Written by Korvus Technology Published on November 3, 2022 The many applications of vacuum deposition processes span industries. Manufacturers use vapour deposition in solar cells, medical implants, LED displays, and other products. Manufacturers and researchers use one of two types of thin film deposition: physical vapour deposition (PVD) and chemical vapour deposition (CVD). Between PVD and CVD, your ideal system will depend on your substrates and application needs, including performance at a high temperature. Below, we explore PVD vs CVD by explaining both techniques and presenting the advantages of each to help you choose your ideal system. What Is Physical Vapour Deposition? Physical vapour deposition takes a solid precursor material and turns it into a gas in a reacting chamber, where the atoms deposit a thin film onto a substrate through condensation. Most PVD coating applications use the following techniques: Evaporation Thermal evaporation vaporises a coating material, turning it into a gas. The released atoms enter a reaction chamber and coat the surface of a substrate material in a very thin layer. Sputtering The sputtering process uses plasma ions moving at high speeds to release atoms from the source material. The atoms in the reaction chamber stick to the target substrate. Korvus Technology’s HEX Series thin film deposition system supports several techniques, including sputtering. What is Chemical Vapour Deposition? Chemical vapour deposition is similar to PVD, but the difference is that CVD uses volatile precursors to deposit a gaseous source material onto the substrate’s surface. Chemical reactions initiated through heat or pressure cause the coating material to form a thin film on the substrate in the reacting chamber. What Is the Difference Between PVD and CVD? While both processes create thin films over substrate materials, PVD and CVD coating techniques differ in several ways: Process The coating process is the main difference between PVD and CVD. Physical vapour deposition uses physical reactions to change a liquid source material to a gas. The material then returns to its solid state as a thin layer on the surface of the substrate. Chemical vapour deposition creates thin films using chemical reactions. The polymerisation and coating phases occur at the same time, which creates copolymers of different monomers for a broad range of applications [1]. PVD and CVD coating processes also differ in how well they coat the substrate. PVD does not perform as well on the sides and back of the coating substrate, whereas CVD techniques produce a uniform thin coat on uneven surfaces. Temperature PVD deposition occurs at a relatively low temperature, up to 450 degrees Celsius. CVD deposition requires higher temperatures above 900 degrees Celsius [2]. Due to the high temperatures, the CVD process often includes heat treatment of the coated surface. Application PVD can improve a substrate’s tolerance to high temperatures and ablation, ideal for glass and decorative coatings, diffusion barriers, and aerospace technology. The high-temperature CVD process creates thin films with superior purity and uniformity. Applications include protective layers, semiconductors, and more [1]. What Are the Advantages of CVD Over PVD? Chemical vapour deposition provides a versatile process for coating the surface of a substrate. When considering PVD vs CVD, keep in mind these advantages of the CVD method: High purity: Many manufacturers prefer CVD for coating materials that require specialised thin films at an exact desired thickness. CVD uses gas coating materials, avoiding the impurities of liquid coating processes. Uniform coating: CVD is a conformal deposition process, which means it uniformly coats a substrate regardless of the shape to produce an even coating. This method builds the desired layer from the substrate up, a significant advantage in creating conductive films [1]. Application variety: Manufacturers use CVD to create thin layers on many materials regardless of rigidity, flexibility, or density [1]. You’ll find CVD systems across industries, from electronics manufacturing to producing crisp bags. CVD can produce large graphene sheets, carbon nanotube arrays, and other essential coated manufacturing materials [3]. Cost: CVD systems cost less than PVD systems. The possibilities of the CVD method continue to expand into new applications. What Are the Advantages of PVD Over CVD? Physical vapour deposition is an often-used method for coating inorganic materials, such as metal and some organic materials. It offers many advantages, including the following: Temperature resistance: PVD films can withstand temperatures over 400 degrees Celcius, making them ideal in the manufacturing of high-performance solar power technology and other applications that require resistance to intense heating [4]. Abrasion and impact resistance: PVD techniques can create a very thin layer of only 2.5 micrometres that provides superior resistance to abrasions. Environmental friendliness: Unlike CVD, PVD does not produce hazardous byproducts and does not use hazardous gases in its processes. Instead of using a reactive gas, PVD uses high-power electricity or lasers to gasify the coating material. Wear-resistant coating: Manufacturers use PVD for many coating applications, including improving wear resistance and reducing the friction of cutting tools, and creating anisotropic glasses for semiconductors. You’ll see examples of PVD use across industries, including architecture, automotive, jewellery, and more. When comparing PVD and CVD costs, PVD tends to cost more than CVD, but many manufacturers consider PVD best for their applications. Conclusion – PVD vs CVD Coating To summarise, PVD and CVD both function as methods of binding the desired layer to a substrate material. The primary difference is that PVD uses a liquid source material to create a thin film, while CVD uses a gaseous source material. PVD and CVD suit different applications, depending on purity, speed, and cost requirements. You may choose a CVD system to form graphene sheets for electronics, or you may select a PVD system for metal coating with plasma ions for solar panels. If you’re looking for a compact, high-performance PVD system, Korvus’ HEX series modular PVD system supports sputtering, thermal evaporation, sample preparation, pulsed laser deposition, and organic PVD thin film deposition. Every vapour deposition application comes with different requirements, and we can provide a custom solution that meets your needs. The versatile HEX series provides the perfect system to teach thin film methodology, research new coatings, or deposit thin films through benchtop production. References [1] Asatekin, A., Barr, M. C., Baxamusa, S. H., Lau, K. K. S., Tenhaeff, W., Xu, J., & Gleason, K. K. (2010). Designing polymer surfaces via vapor deposition. Materials Today, 13:5, 26–33. https://doi.org/10.1016/s1369-7021(10)70081-x [2] Musbah, A., & Eljaafari, W., Fessatwi, E., & Elsahli, Y. (2022). Comparison Between Chemical Vapor Deposition CVD and Physical Vapor Deposition PVD Coating Techniques: A Review Paper. February 2022. [3] David L. Chandler. Explained: Chemical vapor deposition. MIT News | Massachusetts Institute of Technology. https://news.mit.edu/2015/explained-chemical-vapor-deposition-0619. Accessed 02 November 2022. [4] Selvakumar, N., & Barshilia, H. C. (2012). Review of physical vapor deposited (PVD) spectrally selective coatings for mid- and high-temperature solar thermal applications. Solar Energy Materials and Solar Cells, 98, 1–23. https://doi.org/10.1016/j.solmat.2011.10.028

Written by Matt Clancy Published on March 30, 2022 The deposition of a thin-film is a critical manufacturing step involving creating and applying a coating onto a substrate material. The coating can be a compound, metal, or oxide. Each coating has a unique set of characteristics to enhance the substrate and ensure that it is suitable for its application. For example, a coating can protect the substrate against extreme temperatures, scratches, or infrared radiation. A coating can also be transparent or change the conductivity of the substrate. Various methods exist to apply thin films to substrates, and the suitable method depends on the source material, substrate, and application. This guide looks at electron beam evaporation applications, one of the most effective forms of physical vapour deposition, and what this thin-film deposition method entails. To learn more about the equipment necessary for e-beam evaporation, sputtering, and thermal evaporation, read more about the HEX Series from Korvus Technology. Physical Vapor Deposition: What Is E-Beam Evaporation? Various industries use high-vacuum chamber systems for the thin-film deposition of materials, such as insulators or metals, to substrates. The processes for producing these films include physical vapour deposition (PVD) and chemical vapour deposition (CVD). Physical vapour deposition processes are ideal for creating a rigid thin film resistant to extreme temperatures and corrosion. The three primary physical vapour deposition (PVD) methods for thin films include: Sputtering Thermal evaporation Electron-beam evaporation (e-beam evaporation) Sputtering involves plasma generation under high voltage between the source material and the substrate. These methods include ion beam-assisted deposition, reactive sputtering, and magnetron sputtering. Electron-beam and thermal evaporation use an evaporation coating process. An electric current heats the target material during the thermal evaporation process, melting it and evaporating it to a gaseous phase. The vapour cloud travels upwards in the deposition chamber and precipitates against the substrate that requires the coating, forming a thin film. The e-beam evaporation process is similar to thermal evaporation in that it uses evaporation deposition. However, an e-beam evaporation system doesn’t heat the evaporation material using electric resistance. Instead, a charged tungsten filament aims a beam of high-energy electrons at the source material or a crucible containing the target material. The high kinetic energy of the focused electron beam transfers to the target material, which evaporates and deposits onto the substrate. The e-beam has a high electricity density, allowing for the efficient evaporation of high-melting-point materials that don’t sublimate during thermal evaporation. These materials include deposit metals and materials that transition to a vapour phase at high temperatures, including gold, platinum, and silicon dioxide. Electron-Beam Deposition: An Overview of the Thin-Film Deposition Process An electron beam system has two components – the electron gun, containing a filament, and the crucibles, containing the evaporation materials for coating the substrate. The substrate is above the crucible in the vacuum chamber. Heating the tungsten filament [1] is necessary to generate the electron beam. Sending a current of up to 10 kV through the electron gun heats the filament and generates an electron beam via thermionic emission. E-beam generation can also occur via the field-electron emission or anodic-arc method. Depending on the electron-beam configuration, a set of magnets direct the electron beam towards the evaporation materials in the crucibles. When the electron beam hits this source material, the high energy of the electrons converts into heat, evaporating the material. The evaporated material is a vapour stream that traverses the vacuum environment without colliding or reacting with other atoms. When the vapour hits the substrate, it clings to the surface as a thin film. Electron-Beam Evaporation Configurations Three electron-beam evaporation configurations exist: Electromagnetic focusing Electromagnetic alignment Pendant drop configuration E-beam evaporation systems with electromagnetic focusing and alignment configurations bend and guide electron beams towards the source material using a magnetic field. With magnetic field e-beam guidance, direct heat transfer occurs instead of indirect heating via the container. [2] In e-beam evaporation systems with a pendant drop configuration, the evaporation material is in the form of a wire or a rod in the centre of a cathode loop. As the rod’s tip melts, the material evaporates to coat the substrate. Reactive Evaporation vs Co-Evaporation A reactive gas, such as oxygen or acetylene, reacts with the target material vapours near the substrate to form the thin film during reactive electron-beam evaporation. The co-evaporation process involves simultaneously heating a metal and carbon ingot to form a metal carbide film on the substrate. Electron Beam Evaporation Applications in Modern Times The Advantages of E-Beam Evaporation Electron-beam evaporation is a thin-film deposition method with a wide application range. The direct heat transfer between the e-beam and the target material is the most significant advantage of e-beam evaporation over thermal evaporation. Electron-beam evaporation allows for very high deposition rates and high melting temperatures, including: Refractory metals, such as tantalum, tungsten, and graphite Metals with high melting temperatures, such as silicon dioxide and gold With a deposition rate ranging from 0.1 to 100 nanometers (nm) per minute at low substrate temperatures, e-beam evaporation is ideal for achieving a high-density thin film and optimal substrate adhesion. The ability to control the coatings’ reflection of specific wavelength bands is valuable in producing laser optics and architectural glass products. The crucible holding the target material typically has a copper or tungsten construction. [3] Crucibles holding high-temperature materials can also be ceramic. The focused electron beam only heats a small area of the target material, which means there is enough room for multiple crucibles in the high-vacuum chamber. An e-beam evaporation configuration with a four-pocket hearth can contain up to four source materials. This configuration allows for the sequential deposition of four material layers without needing to break the vacuum. During some e-beam evaporation techniques, water cooling the crucible prevents it from heating through thermal energy. Directly heating the source materials also eliminates the risk of heat damage to the substrate. The electron beam only heats the target materials and not the crucible. Keeping the crucible cool throughout e-beam evaporation prevents target material contamination and maximizes material use efficiency, reducing costs. In others, the crucible is the part targeted by the electrons and so is the part of the source being heated, this is turn, indirectly heats and vaporises the material within the crucible. Electron-Beam Evaporation Applications The automotive and aerospace industries typically use e-beam evaporation when constructing components that should have high wear resistance. This process creates rigid chemical barriers resistant to extreme temperatures and corrosive environments, making it ideal for manufacturing cutting tools, machinery components, and marine fittings. Optical Thin Films Multi-layer electron-beam evaporation allows for the production of optical films with unique reflective and transmissive properties. It is possible to achieve specific film properties by layering multiple optical coatings—for example, cold filters that block infrared radiation on a glass substrate. Optical and oxide thin films have multiple uses. Applications requiring optical coatings include the production of architectural glass, laser optics, solar panels, semiconductors, and eyeglasses. Metallic Films With the e-beam evaporation of low-resistance metals, manufacturers can produce various metallic films, including wiring films, decorative films, electromagnetic shielding films, and reflective films. The products requiring metallic film e-beam evaporation during production include: Power packs Organic and inorganic electroluminescent (EL) diode displays Surface acoustic wave (SAW) filters Some components of watches and lithium-ion batteries also have metallic films. Electron-Beam Evaporation Limitations Like thermal evaporation, e-beam evaporation is a line-of-sight deposition method and is unsuitable for coating the inner surfaces of complex geometries. Secondary electron emission and X-ray production can cause incident electron energy loss. During e-beam evaporation, filament degradation can also cause an inconsistent evaporation rate by the e-beam. E-Beam Evaporation System: How Does It Work? Electron beam evaporation involves the acceleration of electrons as a targeted beam to a source material within a crucible. Quartz crystal monitors [4] regulate the thickness of the developing film during deposition. The HEX Series by Korvus Technology includes compact thin-film deposition systems. These high-end systems are suitable for a wide range of research and development applications with sufficient energy for several deposition methods, including: Sputtering Thermal evaporation Electron-beam evaporation Organic physical vapour deposition (PVD) Pulsed laser The Korvus’ thin film deposition systems feature a modular design with a six-sided vacuum chamber that is lightweight but rigid. The systems offer six modular panels that include: A blank panel A viewport panel A deposition source panel A QCM panel for evaporation speed monitoring A pulsed laser deposition (PLD) instrument panel for controlling mass flow and film thickness The HEX deposition systems are highly versatile with standard fittings, including Hamlet gas and water connections. The base HEX system features a multi-sample hearth and supports electron microscopy (EM) sample preparation, new film research, magnetron sputtering deposition optimization, and other methodologies. Final Words E-beam evaporation is among the most effective methods for the deposition of dielectrics and metals with high melting points. Generally speaking, this process offers a higher deposition rate than resistive thermal evaporation or sputtering. Electron beam evaporation also offers exceptional directionality, allowing multiple crucibles and optimal target material heating. The high uniformity and purity levels translate to a high material use efficiency and low costs. These systems are also compatible with ion-assist sources. To learn more about the benefits of other deposition methods, read these articles on thermal evaporation, sputtering, and PVD coating. References [1] Bishop, Charles. (2007) “Electron Beam (E-Beam) Evaporation,” Chapter 15 in Vacuum Deposition onto Webs, Films, and Foils, 239-250. Elsevier Press. DOI:10.1016/B978-081551535-7.50013-6 [2] Wang, Zhongping, and Zengming Zhang. (2016) “Electron Beam Evaporation Deposition.” In Advanced Nano Deposition Methods, 33–58. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. http://dx.doi.org/10.1002/9783527696406.ch2. [3] Madou, M. J., Fundamentals of Microfabrication: The Science of Miniaturization, 2nd Edition. CRC Press (2002), 135–136. [4] Varineau, Pierre T., and Buttry, Daniel. (1987) “Applications of the Quartz Crystal Microbalance to Electrochemistry.” J. Phys. Chem. 1987, 91, 6, 1292–1295. https://doi.org/10.1021/j100290a003

Written by Korvus Technology Published on August 8, 2023 What Is Low-Temperature Thermal Evaporation of Organic Materials? Low-temperature evaporation offers a unique alternative that minimises the energy requirements and high-temperature risk involved in evaporating organic materials. Low-temperature evaporation uses a vacuum chamber to vaporise materials, through thermal deposition techniques. This low temperature in the source allows for temperature-sensitive materials to be deposited effectively and safely. How Low-Temperature Evaporation Works for Thin Film Deposition Many organic materials already have low boiling points, and exposing them to high temperatures during evaporation is unnecessary. By vaporising organics in a low-temperature evaporation system, these materials can avoid being exposed to unsafe levels of heat that could impact their deposition rate and form ineffective films on the target substrate. Because organic materials are extremely sensitive to temperatures, even a small temperature increase during thin-film deposition could cause the organic material to eject from the source. Low-temperature evaporation techniques allow for greater control over the deposition rate and vacuum temperatures of organic materials within physical vapour deposition. By regulating the temperature in the vacuum system, certain qualities of the organic material can be preserved that would otherwise fail within high temperatures, such as concentration and thickness measurements. If the liquid falls below the necessary boiling temperature, a heat exchanger can recover heat from other sources to increase the temperature within the source. Low-Temperature Evaporation Systems for Controlled Deposition Several low-temperature evaporation techniques offer fine control over material heating power, including: Two-stage systems, which provide intermediate gas cooling between two compressor steps Intercooler systems, which use an intermediate evaporation step to cool the discharge gas Cascade systems, which utilise two refrigeration circuits connected by an intermediate cascade heat exchanger Low-temperature vapour systems typically operate in a feedback loop based on thickness measurements, which allows for a highly specialised layer deposition rate. Most systems maintain normal levels of condensing pressure with low evaporation temperatures. Evaporating the material over multiple stages prevents high local pressures from increasing the discharge temperature of the material. However, some materials with high vapour pressures may exhibit isotropic qualities through vacuum evaporation due to the high local pressures in the deposition plume. Meet the ORCA: Our Solution for Organic Material Deposition The ORCA Organic Evaporation Source from Korvus Technology is a vacuum evaporation system that uses low evaporation temperatures and high thermal conductivity to maximise stability and fine control. This user-friendly system makes low-temperature vacuum evaporation accessible to businesses across the UK, especially those in organic electronics manufacturing. The ORCA supports vapour temperatures ranging between 50 and 600 degrees Celsius and uses a K-Type thermocouple that produces highly accurate temperature readings. You’ll enjoy a simplified solution to low-temperature evaporation that perfectly complements the Korvus Technology modular PVD systems. The ORCA low-temperature evaporation source employs active cooling of the crucible to ensure that the heating process is balanced by a strong opposing cooling process which results in excellent temperature stability and control. The crucible is constructed from high thermal-conductivity material, ensuring no hot-spots arise which could distort the evaporation rate. Optionally, alumina or graphite liners may be employed. The crucible (complete with liner if fitted) is easily removed/swapped without the need for any tools, although this is often not necessary since access to the source in order to refill the crucible is rapid and simple. The K-type thermocouple is inserted into the body of the crucible, giving much more accurate readings than typical touch-contact arrangements. The ORCA is supplied with a power unit coupled with a PID controller tuned for low-temperature operation, ensuring precise temperature control. The source may be used in conjunction with sputter sources, e-beam sources, thermal sources, and others. Thermal crosstalk is minimised through the cooled shielding cap. The ORCA is also perfectly paired with our temperature gradient sample stage, allowing precise temperature control of the substrate. The ORCA system is designed specifically for the evaporation of materials at low temperatures (50-600°C). Conventional evaporation sources typically operate at over 1,000°C, which can lead to temperature control issues. The ORCA’s specialised design for low temperatures prevents such issues, making it an ideal solution for organic evaporation processes. Our low-temperature evaporation and modular PVD systems are reliable, cost-effective solutions for forming thin films across numerous industrial applications. To learn how the ORCA can benefit your company, discover more about the Hex PVD system, or better understand PVD coating, contact Korvus Technology today. Low-Temperature Evaporation vs. Standard Thermal Evaporation Low-temperature evaporation stands in contrast to thermal evaporation, exhibiting these unique qualities. Temperature The primary difference between these two evaporation techniques is the temperature required within the chamber and source. Thermal evaporation methods typically heat the source’s materials to temperatures of 1,000 degrees Celsius or higher, though some standard thermal evaporation systems allow for evaporation temperatures of up to 1,500 degrees [1]. Meanwhile, low-temperature evaporation supports temperatures of 600 degrees Celsius and below. These systems are ideal for organic materials that are extremely sensitive to a small temperature increase and need to maintain highly specific properties for their applications. Design These two evaporation systems also utilise different designs. In a low-temperature vacuum evaporation system, the heating element is separate from the material support. This design allows for more control over the material heating power. In contrast, standard thermal evaporation uses emissions at the heated source that immediately condense onto a cold substrate. There is no separation of the heating element from the substrate materials. Properties A material’s evaporation method impacts its properties, requiring developers to choose the right method when forming thin films. For example, TiN coatings produced using a low evaporation temperature of approximately 200 degrees Celsius showed an increase in hardness and residual compressive stress when compared to the same coating produced with a standard temperature method [2]. In the same study, CrN coatings deposited with low-temperature evaporation demonstrated different small-molecule compounds and chemistry than their standard evaporation counterparts. Radiative Loss Evaporation using lower temperatures significantly reduces radiative loss compared to conventional evaporation sources. This method is more suitable for materials that benefit from slow temperature change during organic evaporation. Applications of Low-Temperature Evaporation for Thin Films The industrial applications of low-temperature evaporation are numerous, spanning industries ranging from pharmaceutical to wastewater treatment. Pharmaceuticals Pharmacists have begun developing a bubble column low-temperature evaporation process for dissolving pharmaceutical APIs improving the production efficiency of pharmaceutical compounds [3]. This method can achieve an evaporation rate of up to 6.4 grams per minute within a single stage. Nanotechnology Researchers have successfully used a low-temperature, catalyst-free evaporation route to evaporate ZnO nanoneedles and nanosaws [4], which can be applied in the development of solar cells. Food Science The food science industry is always looking for new methods of drying and concentrating food products to prevent spoilage. Low-temperature evaporation presents a unique, efficient and energy-saving solution to removing liquid from foods. Traditional drying methods are energy-intensive, but low-temperature evaporation methods can reduce water content before sending foods to the dryer, improving the efficiency of the process. Wastewater Treatment Reducing the volume of wastewater through drying or evaporation can minimise storage needs and disposal costs. By using vacuum evaporation, the liquid in the chamber will evaporate at lower temperatures, reducing the amount of energy necessary for evaporation. Oil Field Vacuum evaporation also plays a valuable role in separating water and other small-molecule compounds from oil. Oil companies can reduce operating costs by using energy-efficient evaporator systems to separate oil instead of traditional thermal evaporators. Battery Science Researchers have even begun using low-temperature evaporator systems within the mass spectrometry titration protocol for quantifying inactive lithium in batteries [5]. References [1] Koskinen, J. (2014). Films and Coatings: Technology and Recent Development. Comprehensive Materials Processing, Accessed on 29 June 2023. [2] Gahlin, Rickard, Bromark, Michael, Hedenqvist, Per, Hogmark, Sture, & Greger Hakansson. (1995). Properties of TiN and CrN coatings deposited at low temperature using reactive arc-evaporation. Surface and Coatings Technology, 76-77:1, 174-180. [3] Roche, Phillip, Glennon, Brian, Jones, Roderick C., & Philip Donnellan. (2021). Low-temperature evaporation of continuous pharmaceutical process streams in a bubble column. Chemical Engineering Research and Design, 166, 74-85. [4] Fan, H.J., Scholaz, R., Dadgar, A., Krost, A., & M. Zacharias. (2005). A low-temperature evaporation route for ZnO nanoneedles and nanosaws. Applied Physics A,, 80, 457-460. [5] Tao, Mingming, Xiang, Yuxuan, Zhao, Danhui, Shan, Peizhao, & Yong Yang. (2022). Protocol for quantifying inactive lithium in anode-free lithium batteries by mass spectrometry titration. Communications Materials, Accessed on 29 June 2023.

Written by Bryan Stuart Published on March 29, 2024 An Introduction to Electron Beam Evaporation and E-Beam Evaporators Electronic beam evaporation, also known as e-beam evaporation, is one of the four main forms of physical vapour deposition (PVD). It uses an intense beam of high-energy electrons to evaporate the source material [1], reducing limitations on maximum evaporation temperatures. E-beam evaporation works in a different way to sputtering, which collides energetic ions with a target to sputter or eject the target material. Electron beam evaporation expands upon the applications of thin film deposition common to more traditional vaporisation processes. But which method is better? Is electron beam evaporation what you need from your thin film deposition system? Read ahead to learn the ins and outs of electron beam evaporation, along with its advantages over sputtering, from our Korvus Technology team. The TAU E-Beam Evaporator The TAU e-beam evaporator stands out with its compact framework, uniquely opting out of the use of beam-bending magnets that are common in bulkier counterparts. Instead, it leverages a positive charge to direct a focused electron beam towards a target crucible, with a DC voltage applied to a tungsten filament to initiate indirect heating and evaporation of the material. Central to the discussion on the e-beam evaporator process is the heat management during material vaporisation. The electron beam is accelerated under controlled conditions to minimize excessive thermal build-up. The TAU incorporates an ingeniously designed enclosed head, significantly reducing the thermal footprint within the vacuum chamber. This meticulous design allows for deposition at lower substrate temperatures, making the TAU an invaluable asset for lift-off techniques and the coating of heat-sensitive substrates, ensuring precision and integrity in the final application. The Electron Beam Evaporation Process Electron beam evaporation is a form of physical vapour deposition that uses a focused electron beam within a vacuum environment to heat evaporation material. The e-beam evaporation process is based on the emission of electrons from a tungsten filament when exposed to a current. The electron gun system sends an electric current of sufficient energy, between five and ten kV, through the tungsten filament, which is located outside the deposition area. This high-voltage current heats the tungsten to high temperatures, allowing the thermionic emission of electrons to occur. The e-beam evaporator then uses permanent magnets or electromagnetic focusing to direct the high-energy electrons toward the target material, which is placed in a water-cooled crucible. As the crucible is bombarded with an electron beam, the kinetic energy is converted into thermal energy. This causes the material inside to evaporate, rise through the vacuum chamber and deposit onto the substrate as a thin layer. This focused, high kinetic energy can evaporate high melting point materials not capable of evaporation through traditional deposition methods. It can yield very high deposition rates at low substrate temperatures. This method of thermal evaporation is useful for deposit metals, refractory metals, optical thin films, and a range of other electron beam evaporation applications. The Main Advantages of Electron Beam Evaporation Electron beam evaporation offers excellent precision and versatility. It enables the vaporisation of materials with high melting points, such as tungsten and niobium, and provides exceptional control over the coating process. High-Temperature Thin Film Deposition One significant advantage of electron beam heating is the ability to work with higher deposition temperatures than traditional thermal evaporation. This method of evaporation can vaporise coating material metals with high melting temperatures, such as Tungsten Niobium Silicon dioxide Ruthenium Coating Control Electron beam evaporation allows for high material utilisation and is applicable across a broad range of evaporation materials. Using the electron beam allows for precise control over the deposition rate and monitoring of the growing film on the substrate. Using an electron beam evaporator enables you to create a coating that matches your desired properties, down to a fraction of a nanometre. Substrate Protection Processes like sputtering can cause damage to the substrate because the high-energy particles involved in the sputtering process can physically dislodge atoms from the substrate, leading to erosion or the implantation of unwanted materials. This action can also introduce thermal stresses due to the high kinetic energy of the particles impacting the substrate, potentially altering its physical and chemical properties. Electron beam evaporation, on the other hand, minimises damage to the substrate as it utilises an electron beam to heat and evaporate the source material in a vacuum. This method allows for more precise control over the deposition rate and substrate temperature, reducing the risk of thermal damage. Additionally, since the process is less aggressive compared to sputtering, there’s a lower likelihood of substrate alteration or damage from high-energy particle impacts. Applications Electron beam evaporation applications vary between ceramic coating deposition [2], the growth of zinc oxide thin films [3], creating coatings to protect surfaces in corrosive environments, and more. One of the most promising uses of electron beam evaporation is within laser optics. The thin films produced by this thermal deposition process are ideal for optical coatings, such as those on solar panels, eyeglasses, architectural glass, and more. Electron beam evaporation is also applicable in the aerospace and automotive industries. These industries often have high temperature requirements and strict guidelines for the wear resistance of their materials. Comparing Electron Beam With Other Thin-Film Deposition Processes A common question is, “How do I know if I should use e-beam over deposition methods?” The thin films deposited with different PVD techniques vary, as well as different procedures being suited to different coating materials. Take a look below to see common comparisons. E-Beam Evaporation vs Thermal Evaporation E-beam evaporation is used over thermal evaporation when high energy and precise control over the evaporation rate and substrate temperature are required. This method is particularly beneficial for materials that have very high melting points or those that are sensitive to thermal decomposition. With that being said, thermal evaporation is a great choice if you are working with materials that evaporate at lower temperatures and require a simpler, more cost-effective setup. Thermal evaporation can offer a uniform and high-quality coating for a wide range of materials, making it suitable for applications where material properties allow for its use. E-Beam Evaporation vs Sputtering Electron beam evaporation and sputtering both have a range of applications. However, electron beam physical vapour deposition allows for the vaporisation of high-melting-point materials with a relatively low deposition time [4]. E-beam evaporation is more suitable for high-volume batch production and thin-film optical coatings. While sputtering is applicable to some optical processes, its applications are more limited. As such, sputtering is more commonly used within applications requiring high levels of automation. FAQs About E-Beam Evaporation How Is Sputtering Different from Electron Beam Evaporation? While sputtering and e-beam evaporation are both forms of physical vapour deposition, their deposition processes differ significantly. Electron beam evaporation is a form of thermal evaporation. The thermal evaporation process focuses an electron beam on a source material to produce very high temperatures, allowing it to vaporise high-temperature materials. Meanwhile, magnetron sputtering collides positively charged energetic ions with a negatively charged target material, ejecting atoms from the target material and depositing them onto a substrate. Sputtering occurs within a closed magnetic field, while electron beam evaporation occurs within a vacuum or deposition chamber. Both sputtering and e-beam evaporation have a low level of impurity, but e-beam PVD has a higher deposition rate. However, sputtering has the highest rate of scalability, as it can be automated in many applications. In some cases, using ion-beam-assisted deposition, such as that involved in sputtering, can expand the functionality of thermal evaporation. Understanding the right evaporation system, or the right combination of systems is essential to optimising precision, functionality, and efficiency in your desired application. What Are the Disadvantages of E-Beam Evaporation? While electron beam PVD has some industrial applications, it is not suitable for coating the inner surface of complex geometries. Additionally, the filament degradation used within this vaporisation process can produce a non-uniform evaporating rate, producing less precise results than other methods. Evaporation deposition also has limited scalability with a lower utilisation and deposition rate. Further, this system is relatively complex, leading to a higher cost compared to other deposition methods, like pulsed laser deposition or chemical vapor deposition. Weighing up the advantages and disadvantages of this thermal evaporation technique can help you determine whether it is suitable for your application. References [1] Bashir, Almas, Iqbal Awan, TAhir, Tehseen, Aqsa, Bilal Tahir, Muhammad, Ijaz, Mosin. (2020, May 27). Interfaces and surfaces. Chemistry of Nanomaterials. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/pii/B9780128189085000032 [2] Shamala, K. S., Metzner, C., Maiti, N., Zhigarev, A. A., Evans, ?., Kanareykin, A. D., Ganz, S. N., Avdeeva, D. K., Garshin, A. P., Balkevich, V. L., Kunevich, A. V., … Hocking, M. G. (2017, June 19). Ceramic coating deposition by electron beam evaporation. Surface and Coatings Technology. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S025789721730645X [3] Caglar, M., Fang, G. J., Karuppasamy, A., Asmar, R. A., Zhu, B. L., Daniel, G. P., Fang, Z. B., Zhang, D. H., Chu, S. Y., Zhaoyang, W., Li, X. H., & Kim, D. C. (2011, March 29). Effect of heat treatment on characteristics of nanocrystalline ZnO films by electron beam evaporation. Vacuum. Retrieved December 28, 2022, from https://www.sciencedirect.com/science/article/abs/pii/S0042207X11001205[4] Maiti, N., Karmakar, P., Barve, U. D., & Bapat, A. V. (2008). An evaporation system for film deposition using electron beam sources. IOPScience. Retrieved December 28, 2022, from https://iopscience.iop.org/article/10.1088/1742-6596/114/1/012049

Written by Korvus Technology Published on November 10, 2022 Sputtering: What is it and how does sputter deposition work? Most people are familiar with the three states of matter: solid, liquid, and gas. However, gaseous plasma exists as a state apart. This unique dynamic condition creates a flux of neutral gas atoms coexisting with electrons, photons, and accelerated ions in the same space. Since plasma consists of unstable high-energy particles (i.e., ions and electrons), it needs an external energy source like powerful voltages or high temperatures. Gas plasma has many uses across different industries, one of which is a surface modification by sputter deposition. Physical sputtering[1] is a thin film creation method that directs accelerated ions from the source material onto a target surface to create a coating. This technique has applications in the semiconductor industry and solar panels, disk drives, optical devices, and other major industries. This overview covers the basics of the sputter deposition method and its advantages compared to other deposition methods. What Does Sputtering Mean? The word “sputtering” originates from the Latin “Sputare,” which means “to spit out noisily.” You may picture a spray fountain made up of tiny moist particle flux. While crude, this image depicts the gaseous plasma-based sputter remarkably well. People who deal with car mechanics may also associate “sputter” with the series of explosive noises an engine makes when it overheats and is about to give out. In industrial physics, however, the meaning of “sputtering” has an entirely different context. This process is one of many forms of Physical Vapour Deposition (commonly refer as PVD). One of its most widely used alternatives is the thermal deposition method. Sputtering is a process that enables the creation of film coating made of sputtered atoms. Without this method, it would be nearly impossible to attain the high-quality coating films necessary for LED displays, optical filters, precision optics, and more. Plasma sputter began in 1970 [2] when Peter J. Clarke presented the first sputtering device that used electron and ion collisions to deposit an atom scale coating on a target surface. Today, more than five decades later, thin film applications form an inseparable part of aerospace, solar energy, microelectronics, automotive, and other industries. The Sputtering Process The sputtering process starts with placing the substrate (the surface that requires a coating) in a vacuum chamber filled with inert gas atoms. The source material, which will transfer onto the substrate, then receives a negative charge and becomes a cathode. This causes free electrons to flow from the charged source materials. These electrons collide with the outer electrons surrounding the gas atom, which has the same negative charge, driving the gas electrons off. Once it loses electrons, a neutral atom turns into a high-energy ion. When the cathode target is bombarded, electrons get knocked out due to the collisions, and the gas atoms turn into positively charged ions. The negatively charged source material attracts these positive ions, which fly at it with such high velocity that atomic-sized particles “sputter off,” or detach. Finally, the sputtered particles cross the vacuum chamber and start landing on the substrate surface as a growing film made of ejected target ions. How Does Sputtering Work? Sputter systems come in different sizes, depending on the industry application. The process happens in a vacuum chamber. Glass (e.g., architectural glass, solar cells, and so on) is the most common substrate for the film coating. Korvus Technology manufactures the HEX Series, a sputtering system capable of several thin film deposition techniques. The sputter coating is one of the most common applications of this incredibly versatile and efficient system. What Is a Sputtering Target? The film material source is a rotary target made of metal, ceramic, or even plastic. As an example, let’s take a molybdenum target. Molybdenum often functions in producing conductive thin films in displays or solar cells. Throughout the process, pumps keep removing air to create a vacuum environment. The base pressure in the chamber is around 10 to -6 millibar or about a billionth part of the normal atmospheric pressure. Inert gas atoms flow continuously into the deposition chamber, creating a low gas pressure atmosphere. In physical vapour deposition,[3] a magnet array may sit inside the cylindrical target, releasing a magnetic field. Cooling water inside the target cylinder dissipates the heat generated in the process. How does a sputter coater work? Under high voltage, the molybdenum target creates a gaseous plasma, which concentrates along with the magnetic fields. The plasma consists of gas atoms, free electrons, and positively charged argon ions. Continuous electron collisions with the argon atoms keep producing positively charged ions. Since the target surface, or the cathode, is negatively charged, its binding energy attracts the energetic ions. As the target gets bombarded, ions displace atoms. You could think of it as a billiard ball that collides with another ball and sends it rolling. The sputtered atoms gradually settle on the glass substrate, or the anode, which sits opposite the target. Layer by layer, these ejected atoms form a thin film. This process’ deposition rate calculation depends on various factors, such as the target material’s physical properties, the current, and beam energy. Target Surface Quality Ions that hit the target surface don’t distinguish between the desired target atoms (e.g., molybdenum) and any impurities with the same charge. Any atoms that get ejected may consist of both. If the target surface contains impurities, they may end up on the substrate as sputtered atoms and compromise the thin film properties, such as its electrical conductivity. To ensure high-quality thin film, the process must use a highly pure target by a trustworthy manufacturer as well as high-performing equipment. The Role of Argon Argon works well in sputter systems because it is an inert gas with high-mass ions. However, the reactive method may also use a non-inert gas, such as oxygen or nitrogen. In reactive setups, gas ions recombine with the target material to produce the deposited film. Ion Beam Sputtering Ion beam sputtering is a thin film deposition method in which an ion source sputters a target metal or dielectric material onto a substrate. The monoenergetic and highly collimated properties of the ion beam enable precise control of film growth. The result is a highly dense, superior quality film. DC vs RF Sputtering DC sputtering uses a DC (Direct Current) power source. This method is widely used, effective, and economical. It allows the processing of large substrate quantities. The RF sputtering method uses a high voltage AC (Alternating Current) power source and works for both conductive and non-conductive sputtered material. The RF stands for radiofrequency. This technique is more expensive and has a lower sputter yield, making it more suitable for lower substrate sizes. Magnetron Sputtering Magnetron sputtering[4] relies on magnetic fields to control the velocity and direction of charged ion particles from the magnetron sputtering source. Although diode sputtering can yield atomic-scale thin films, it is a slow process that works best with a limited-size substrate. Moreover, particle bombardment can cause overheating and damage the substrate. In magnetron sputtering, magnets placed behind the cathode will trap electrons and prevent them from bombarding the substrate, creating faster deposition. Benefits of Magnetron Sputter Deposition Unlike other technologies, magnetron sputtering does not call for the source materials’ melting and evaporation. This process works for nearly all materials, regardless of melting temperature. The magnetic field technique allows the use of compounds and alloys as magnetron sputtering sources while maintaining their composition as similar as possible. The Advantages and Applications of Sputtering Deposition Sputter deposition can only occur when the bombarding particles have extremely high kinetic energy, which allows the creation of gas plasma. This method enables a pure and accurate atomic-level film deposition, infinitely superior to any conventional thermal energy techniques. The energy transfer of the bombarding particles,[5] the target atom and ion relative masses, and the target atoms’ surface binding energy all control the sputter yield, which is the average number of atoms that fly off from the source material. The process yield’s outstanding precision and constant rate allow the exact programming of the sputtering coating thickness. Compared to other deposition methods such as thermal evaporation, sputtering works well with a broader range of materials, including diverse mixtures and alloys. Its higher energy transfer produces better surface adhesion, more uniform films, and higher packing densities, even at low temperatures. Many industries rely on high-quality thin films produced by the aforementioned deposition methods. Here are just a few examples: The optoelectronics industry, such as optical filters and precision optics Medical devices and implants Consumer electronics and LED displays Fibre lasers and semiconductor lasers Microscopy and microanalysis sample slides Sputtering film deposition is a diverse field with many methods and techniques. It includes RF and DC magnetron sputtering, ion beam sputtering, reactive sputtering, and more. Final Words The sputtering deposition has brought innovation and superior performance to a wide array of industries. The method comprises many sub-techniques, all of which use high-energy collisions to create a thin, precise coating of material. Magnetron sputter deposition further expanded the range of applications and substrates. The final film quality depends on several factors, including target material properties, process methodologies, and sputtering system performance. Are you interested in learning more about sputtering? We invite you to read other blog articles from Korvus Technology, manufacturer of the innovative HEX Series of modular thin film deposition systems that use physical vapor deposition methods. References [1] Berg, S., et al. Fundamental understanding and modeling of reactive sputtering processes. Thin Solid Films Volume 476, Issue 2, 8 April 2005, Pages 215-230. [2] Greene, J. E. Review Article: Tracing the recorded history of thin-film sputter deposition: From the 1800s to 2017. Journal of Vacuum Science & Technology, Volume 35, Issue 5, 10 May 2017. [3] Rossangel, S. M. Thin film deposition with physical vapor deposition and related technologies. Journal of Vacuum Science & Technology, Volume 21, Issue 5, 17 June 2003. [4] Safi, I. Recent aspects concerning DC reactive magnetron sputtering of thin films: A review. Surface and Coatings Technology, Vol 127, Issues 2-3, 22 May 2000, Pages 203-218. [5] Mattox, D. M. Particle bombardment effects on thin‐film deposition: A review. Journal of Vacuum Science & Technology, Volume 7, Issue 3, 04 June 1998.

Written by Bryan Stuart Published on April 24, 2022 Thin Film Deposition By Thermal Evaporation Systems Thermal evaporation is a common physical vapour deposition (PVD) method. This basic form of PVD involves the use of resistive heating at high temperatures in a high vacuum chamber to cause solid material evaporation and create high vapour pressure. Then, the stream of evaporated material coats the surface of the substrate present in the vacuum chamber. As a thermal evaporation technique, thin-film deposition has many industrial applications, including the creation of metal bonding layers in solar cells, thin-film transistors, semiconductor wafers, and carbon-based OLEDs. A film can consist of a single component or form co-deposition layers of different materials. How does thermal vapour deposition work? What does this type of thermal evaporation system involve, and what is the role of high-temperature PVD in the thin film manufacturing industry? What Is Thermal Vapour Deposition? As the term implies, thermal deposition[1] requires heat. In a high vacuum chamber, a heat source acts on a solid material to produce vapour pressure. Most thermal evaporation systems provide an evaporation temperature ranging from 50 to 2500 degrees Celsius to bring the source materials from a solid state to vapour. The basic unit of a thermal evaporation system is a vacuum chamber that holds the substrate and the source material. The source material typically sits at the lower part of the chamber, while fixtures hold the substrate in an inverted position at the top. Thanks to the vacuum environment, even comparatively low vapour pressure can produce a vapour cloud. Once this happens, the vapour stream consisting of evaporated particles can traverse the chamber and stick to the substrate surface as a thin film coating. The reistive evaporation process is one of the most straightforward and efficient forms of physical vapour deposition (PVD). This common method provides cost-effective tools to create thin films of both metals and nonmetals like oxides and nitrides. Compared to the sputtering process, it produces higher deposition rates and thicker coatings, allows fast flash evaporation, and works particularly well for applications that use electric contacts. Breakdown of the Thermal Deposition Process In principle, thermal evaporation deposition consists of basic processes and is one of the oldest technologies in the thin film industry. Unlike thermal chemical vapour deposition, it does not require complex precursors or reactive gas. A simple schematic diagram can help illustrate the method. For thermal evaporation to occur, the deposition chamber must supply proper conditions, namely a high-vacuum environment and a temperature that is high enough to turn the target atoms of the source material into vapour. The Vacuum Chamber Environment Effective thermal evaporation requires a high-vacuum environment to remove the gas particles that may interfere with deposition. A vacuum pump creates and maintains the vacuum in the thermal evaporator. In some systems, the vacuum chamber has low pressure around the source material and high pressure in the substrate area. The bottom of the vacuum chamber contains the heater evaporator, which holds the source material and provides joule heating to bring it to the required temperature. Physical Vapor Deposition The heat dissipation of the source material creates vapour pressure. As the vapour stream rises, it meets the substrate. Then the evaporated materials condense on the target material surface to form a solid film. The substrate holder in the chamber rotates continuously to ensure that the deposited film creates an even layer. PVD works on both metals and nonmetals and on many types of substrates, such as silicon wafers and various polymers. Other Considerations The thin film quality depends on several factors, including the pressure in the vacuum chamber, the source material’s molecular weight and evaporation rate, and the substrate holder’s rotation speed. A higher degree of vacuum will give the source material molecules an improved free path and reduce any impurities in the film. In contrast, a rough surface of the substrate may cause non-uniform deposition. The thermal evaporation deposition method may work less well for materials with a very high melting point. Thermal Evaporation Systems and How They Work Industrial thermal evaporation deposition systems must operate under precise conditions to ensure film purity. The two main subdivisions of thermal evaporation processes are Filament Evaporation and Electron Beam (E-Beam) Evaporation. The first method involves resistive evaporation filaments, also known as “boats.” Essentially, these are thin sheets of metal, often tungsten, that act as an evaporation source and hold the source material in appropriate-sized indentations. Filament evaporation is comparatively safe thanks to low voltage. However, this method requires very high currents. Other thermal evaporation systems apply the more high power density method of E-Beam Evaporation. This method involves high voltages (typically upwards of 10,000 volts) and requires specialised safety features. The energy source is an electron beam “gun” that accelerates electrons using high voltage and directs them as a targeted beam. This electron beam hits the crucible that contains the source material. Many E-Beam systems have several crucibles that hold multiple sources of material at once to enable seamless co-deposition and multi-layer coating.[2] To control evaporation speed and thermal evaporation deposition rate, most thermal evaporation systems use quartz crystal monitors (QCMs) to measure and regulate deposited film thickness. Thermal evaporation systems may also use various software or hardware configurations to manage evaporation rate and film properties. Introducing Korvus Technology’s Thermal Evaporation System Our TES thermal evaporation source is one of the many customisations you can add to the HEX benchtop coating system, HEX-L or HEX-XL. The Korvus TES thermal boat sources are designed for easy removal and quick refilling with new evaporant material. They also support the straightforward and rapid replacement of boats and filaments. Offered as a unit with one source per flange, these TES sources can also be outfitted with thermocouples to keep an eye on the boat temperatures. Users have the option to equip each source with either a manual or an automatic shutter. Systems can integrate multiple sources, and these sources are designed to work alongside other deposition technologies like sputtering, e-beam deposition, and low-temperature sources. If you are interested in seeing if it is right for you, you can learn more about the TES here. What Kind of Material Is Used in the Thermal Evaporation Process? There are several examples of commonly used thermal evaporation sources. Metals, alloys, and ceramics can all work as source materials for evaporated films in thermal evaporation deposition. Thermal evaporation can deposit chrome, aluminium, silver, gold, and many other metals. Generally, resistive evaporation works best for elemental materials with a uniform melting point. Since E-Beam evaporation debuted as a thermal evaporation technique over 50 years ago, it has enabled effective deposition in high-temperature source materials like transition metal oxides. These materials, which include SiO2, HfO2, Al2O3, and others, often function as UV coatings. Thermal evaporation is a thermodynamic process with some inherent instability. To achieve more uniform processes and higher film purity, starting materials often undergo special processing like pre-melting, additive mixing, density control, and producing conductive sub-oxides. E-Beam evaporation may also use ion assist (IAD) for more stable, higher-density films.[3] However, even with the technological advancements of the past decades, E-Beam deposition may not offer enough accuracy for producing high-precision optical coatings in the astronomy, biotech, medical, and aerospace industries. These applications have mostly transitioned to other film deposition methods, like sputter deposition processes, that offer improved step coverage. The Applications of Thermal Vapour Deposition Thermal evaporation deposition has many industrial applications, including: Optics. Manufacturers use thermal evaporation to produce optic and ophthalmic lens coatings. Thermal evaporation can create hard coatings, anti-reflective layers, mirror coatings, and layers that protect against UV or infrared light. Electronics. Thermal evaporation works well for ultra-thin metal plating on devices such as OLEDs and solar cells.[4] Consumer packaging. Packaging foils are among the largest-scale applications of thermal evaporation. Many foodstuffs benefit from improved shelf life and prolonged freshness thanks to a thin aluminium film applied to plastic packaging.[5] Jewellery and accessories. Costume jewellery, accessories, buttons, and other apparel elements also often benefit from the aesthetic effects of a thin film coating deposited by thermal evaporation. In accessories, thin metal plating enables to keep production affordable and cost-effective. Choosing a thermal evaporation method and investing in an industrial-scale system will influence a manufacturer’s entire line of production. When manufacturers plan to invest in the thermal evaporation technique, they should consider elements such as quality, consistency, film purity, and more. Naturally, requirements will vary by line of production. Film quality that is acceptable in accessories or consumer packaging may not provide adequate optical or electrical properties for precision lenses or organic photovoltaics. When commercial enterprises choose industrial-scale thermal evaporation systems, it’s important to make sure that, first, the system works well for the materials the company plans to apply as thin-film coatings, and second, that the system uses adequate quality controls like quartz crystal sensors or optical monitoring systems. The base pressure in the vacuum chamber also plays a crucial role in the final product’s quality. Most systems should supply a partial pressure of 10(-07) to 10(-05) mbar to ensure that the evaporated material has a sufficiently long mean free path and avoid scattering of vapour particles by residual gases. An adequate base pressure level is also important for providing a clean substrate surface and a stable coating. Thin-Film Deposition by Thermal Evaporation: Final Words Thin-film coatings have come a long way from antique metal platings to today’s precise and advanced thin-film deposition systems, like the HEX Series by Korvus Technology. Thermal evaporation deposition, an early and common method of thin-film deposition, retains an essential place in various industries, including optics, electronics, and solar cells. Thanks to its high deposition rate and material utilisation efficiency, thermal evaporation has the edge over other methods in thin-film applications. Advanced technologies such as E-Beam deposition help thermal evaporation produce high-quality coatings with an excellent degree of accuracy. Are you interested in further details about thin films and their applications? Browse other articles on thin film deposition by Korvus Technology. References [1] Bashir, A., et al. 2020. Chapter 3 – Interfaces and surfaces. Chemistry of Nanomaterials, Fundamentals and Applications. Elsevier Press. Pages 51-87. [2] Körner, C. 2016. Additive manufacturing of metallic components by selective electron beam melting — a review. International Materials Review. Volume 61, Apr 2016, Issue 5. [3] Yang, T., et al. 2006. Effect of N2 ion flux on the photocatalysis of nitrogen-doped titanium oxide films by electron-beam evaporation. Applied Surface Science. Volume 252, March 2006, Issue 10. [4] Bello, M., and Shanmugan, S. 2020. Achievements in mid and high-temperature selective absorber coatings by physical vapor deposition (PVD) for solar thermal application – a review. Journal of Alloys and Compounds. Volume 839, October 2020. [5] Struller, C.F., et al. 2014. Aluminum oxide barrier coatings on polymer films for food packaging applications. Surface and Coatings Technology. Volume 241, February 2014, pages 130-137.

Written by Korvus Technology Published on March 1, 2024 Thin Film Deposition Techniques and Systems Thin films are an inseparable part of modern technology. When deposited on the surface of an object, thin film coatings can alter its qualities, for example, increasing durability, changing electric conductivity, or improving optical properties. But how do we define a ‘thin film’? A thin film is a layer of material ranging in thickness from sub-nanometres to microns. A few popular examples of thin film deposition techniques are physical vapour deposition (PVD), chemical vapour deposition (CVD) and atomic layer deposition (ALD). The history of thin solid films begins in antiquity [1], with metallic films (usually gold platings) used on various artefacts for decorative and protective purposes. Today, many industries rely on precise atomic layer deposition (ALD) to produce high-purity thin films. Industrial applications include thin film solar cells, optical lenses with a high refractive index, anti-reflective optical coatings, semiconductor devices, light crystal displays, and more. In this article, you’ll find out more about thin films and the thin film deposition process. What is Thin Film Deposition? The thin film deposition process may vary depending on the techniques used, but all the methods we will discuss here involve placing a thin layer of deposited film on the substrate surface within a vacuum chamber. The first creation of metal films by chemical vapour deposition took place in the mid-17th century. Experiments in oxide deposition began circa 1760, while sputter deposition took its first steps in the 1850s [2]. By the 1930s, manufacturers already used early-stage thin films for high-reflectivity mirrors. The 1960s technologies of ultra-high vacuum and in situ electron microscopy enabled the creation of more advanced, pure, and uniform thin films. In 1970, Peter J. Clarke launched the first sputter gun that created atomic-scale films by using ion and electron collisions. Advanced technologies, such as atomic resolution surface imaging, allowed the progress of the thin film industry as we know it today. Methods for depositing thin films, such as sputtering-based methods, continue to grow and develop into new applications. Physical vapour deposition (PVD), which involves the vaporisation and depositing of solid material on a substrate, encompasses a range of methods from a basic evaporation process to magnetron sputtering and pulsed laser deposition [3]. Many advanced thin-film devices, like the HEX Series by Korvus Technology, use physical deposition methods. PVD, in particular sputtering systems, allow manufacturers to create highly precise and uniform thin films. In contrast, chemical vapour deposition relies on a reaction between precursors in the deposition chamber. CVD has several common uses, like creating Si thin films. A potential drawback of CVD however, is the need for extra-high temperatures to incite the process. The Different Thin Film Deposition Techniques: Physical Vapour Deposition and Chemical Vapour Deposition Deposition techniques fall into two main groups: physical vapour deposition and chemical deposition. Physical Vapour Deposition (PVD) and Chemical Vapour Deposition (CVD) differ fundamentally in their deposition methods. PVD involves the physical transfer of materials under vacuum, where vaporised materials condense onto the substrate, making it ideal for metals and alloys. In contrast, CVD utilises chemical reactions at elevated temperatures to deposit materials from a vapour phase, suitable for complex compounds and polymers. PVD offers precise control over thickness and purity, whereas CVD excels in achieving uniform coatings over intricate shapes. The choice between PVD and CVD depends on the required material properties and the specific demands of the application. See more: PVD vs CVD Physical Vapour Deposition Methods There are a wide range of thin film deposition techniques and choosing the best deposition method for you will depend on numerous factors. Things to bear in mind as you make your decision are: The target material The substrate The required deposition rate Your application Budget available At Korvus Technology, the HEX Series is a physical vapour deposition coating system, covering a range of techniques which we will explore below. Thermal Evaporation Thermal evaporation deposition occurs in a chamber under the pressure of 10(-7) to 10(-5) mbar. A crucible that connects to a high-current source holds the target material. Here are the basic steps for thermal evaporation deposition: A current is applied to the source and the material in the crucible is resistively heated. This will eventually vaporise the material and release the vapour into the chamber. The vapour stream then crosses the chamber and coating particles attach to the substrate generating a thin film of the evaporated material. Throughout the process, the vacuum pump keeps working to maintain a high-vacuum environment and ensure a free path for the film particles. Magnetron Sputtering Sputtering is a physical phenomenon leveraged by thin film deposition to expel microscopic particles of solid materials from their surface. This ejection is achieved by attacking the solid material with energetic particles. The particles are then deposited in the target materials forming the thin film layer. Like other deposition methods, sputtering takes place in a chamber with a vacuum pump constantly working to remove air. The vacuum is a crucial condition for this process, which occurs naturally in outer space. Magnetron sputtering involves the following steps: An inert gas, usually argon, flows continuously into the chamber. Magnet arrays within the vacuum chamber generate a magnetic field. The high voltage creates a gaseous plasma near the target’s magnetic field. The plasma contains argon gas atoms, argon ions, and free electrons. Electrons that hit argon atoms continuously create more positively charged ions. The negatively charged sputtering target attracts the positively charged ions. As the ions hit the target, they eject atoms through a process called ion bombardment. The ejected atoms settle on the substrate’s surface and create a thin film of the target used on the magnetron. Electron Beam Evaporation Electron beam evaporation is a process where a focused electron beam vaporises a target material, causing it to condense and deposit material onto a substrate. This technique is preferred over thermal evaporation due to its precise control over the deposition rate and film thickness. It is particularly beneficial for materials with high melting points, ensuring the deposited material maintains purity and quality without substrate contamination. Thus, electron beam evaporation is selected for its superior efficiency and effectiveness in producing high-quality thin films. Learn More About Electron Beam Evaporation Low-Temperature Organic Evaporation Organic evaporation involves heating organic materials until they vaporise, allowing the material to be deposited onto a substrate, but having a precise control of temperature due to the nature of many organic substances. This method is particularly suited for organic compounds that are sensitive to high temperatures or electron beam exposure. Low-temperature evaporation is chosen for its ability to gently deposit thin films of organic materials, such as polymers and organic semiconductors, without altering their chemical structure. It ensures the integrity of the material to be deposited, making it ideal for applications in organic electronics and bio-compatible coatings. Meet The HEX: A Modular Thin Film Deposition System The HEX Series offers a flexible array of thin film deposition systems tailored for both research and practical applications. Initially, you can acquire the basic model and progressively enhance it with advanced components based on your desired film thickness, materials and other requirements. This makes it suitable for many applications. These components are designed for easy integration, minimising both the downtime of the system and the cost of installation. This series is comprised of the compact HEX model and the more spacious HEX-L and HEX-XL Systems. See more: Comparing The HEX and HEX-L The HEX Glovebox Integration Types of Thin Film Coatings and What They’re Used For Thin films are coatings deposited upon a substrate material (like a silicon wafer, electronic part, or optical lens). Depending on the material and purpose, the film thickness can be anything from one atomic layer to several micrometres. Different applications will call for distinct types of thin films. These include: AR/HR (antireflective or high-reflectivity) coatings alter the optical properties of a material, for example by filtering visible light or deflecting a light beam. Common uses for these thin films include electronic displays, low optical thickness lenses, and output mirrors. TCO (transparent conductive oxide) coatings are electrically conductive, transparent coatings with many uses in touchscreens, LCDs, and photovoltaics. One example is hydrogenated microcrystalline silicon-germanium thin films in solar cells. DLC (diamond-like carbon) thin films increase the coated object’s hardness and scratch resistance. These electrically resistive protective coatings improve the lifespan and durability of microelectronics, medical devices, sensors, and more. Biocompatible hard coatings protect implanted devices, biosensors, and artificial limbs to improve the devices’ longevity and prevent contamination. Biocompatible thin films typically use compounds like titanium nitride and chrome nitride. In this article, we discuss two main deposition techniques: physical vapour deposition (PVD) and chemical vapour deposition (CVD). These methods have shown significant advantages over other techniques, like dip or spin coating, in most applications. Physical vapour deposition involves vaporising materials in a low-pressure chamber to deposit them upon a substrate. Films deposited by PVD can create highly durable, corrosion-resistant coatings that tolerate exposure to high temperatures. Chemical vapour deposition typically involves chemical reactions between precursors, which combine to create a thin film coating on the substrate surface. CVD may involve several advanced techniques, such as reactive ion etching. How PVD is Used to Create Thin Films in The Industry As we’ve discovered, thin film processes have applications in various fields and form the cornerstone of many industries today. Thin films are used in semiconductors, medical devices, fibre lasers, LED displays and much more. Here are just a few examples of advanced applications of thin film technology: Solar cells. A thin film solar cell owes its energy generation properties to the layer of silicon thin film (also known as “Si Thin Films”) deposited on a glass or metal substrate. Second-generation Si thin film solar cells are flexible and lighter than crystalline silicon cells, which enables applications like photovoltaic glazing [4]. Amorphous silicon, a non-crystalline form of silicon, is an affordable substrate that helps reduce the cost and scale the production of thin film panels. Read more about thin film solar cells Thin film transistors. Thin film transistors are a vital component of liquid crystal displays. This type of transistor is inexpensive, energy-efficient, and offers better response time. Read more about thin film transistors Thin film batteries. A thin film battery is more efficient, charges faster, and lasts longer compared to a conventional Li-ion battery. This type of battery can improve the performance of medical products, implants, smart cards, and green energy storage banks. Read more about thin film batteries The thin-film industry keeps evolving. Researchers never stop looking for ways to improve the purity, accuracy, optical properties, and other qualities of thin films. Meanwhile, industry experts work towards reducing costs and overcoming scaling obstacles in thin film production. To implement thin film deposition in your production chain, you’ll need to deploy a thin film deposition system. Learn More: The HEX Series Cluster Systems Korvus Technology is a reliable provider of modular deposition systems and other thin-film accessories and components for laboratories and manufacturers. Thin Film Deposition Technologies: Final Words The world as we know it today relies on thin films. Thin films are everywhere, from a bag of crisps to the device you are using to read this article. Often invisible, thin films are the quiet superheroes of modern industry, with a range of uses from prolonging shelf life to improving optical properties of lenses. Thin films may consist of metals, oxides, and organic materials. The technologies for making thin films vary depending on the application and industry demands. If you are interested in learning more about thin films, we invite you to browse other articles at Korvus Technology. References [1] Greene, J.E. Review article: Tracing the 5000-year recorded history of inorganic thin films from ∼3000 BC to the early 1900s AD. Applied Physics Reviews, Volume 1, Issue 4, 22 July 2014. [2] Greene, J. E. Review Article: Tracing the recorded history of thin-film sputter deposition: From the 1800s to 2017. Journal of Vacuum Science & Technology, Volume 35, Issue 5, 10 May 2017. [3] Baptista, A., et al. On the Physical Vapour Deposition (PVD): Evolution of Magnetron Sputtering Processes for Industrial Applications. Procedia Manufacturing, Volume 17, 2018, Pages 746-757. [4] Luceño-Sánchez, J.A., et al. Materials for Photovoltaics: State of Art and Recent Developments. International Journal of Molecular Sciences. Volume 20, Issue 4, 23 February 2019.

Written by Matt Clancy Published on July 12, 2022 Thin Film Solar Cells and Solar Panels: Everything You Need To Know When people think about solar energy materials, they often mean crystalline silicon (c-Si) cells, the most popular solar technology. Many don’t realise that thin film solar cells are another excellent option for converting visible light into useable power output. Professor Karl Böer discovered the potential for combining thermal collectors and thin film photovoltaic cells in 1970. By 1986, the first commercial thin film technologies became available to the public. Below we discuss everything you need to know about thin film technology and solar panels. What Are Thin Film Solar Cells and How Do They Work? Thin film solar cell technology is a second-generation evolution from c-Si modules made by applying one or several layers of thin photovoltaic materials atop different elements, like glass, metal, plastic, or a combination of each. The thin layers allow for more flexible and lightweight applications compared to the first-generation c-Si technology. While thin film solar panels use less semiconductor material during manufacturing, they still rely on photovoltaic (PV) energy. The electrons inside the thin film PV module’s semiconductor shift positions, creating a harnessable electric flow that an external circuit can convert into useable electricity. Thin film panels typically offer lower costs and less efficiency than c-Si models. Thin film solar efficiency directly depends on the materials, including the growth technology and semiconductor. While they do not have a reputation for offering high-efficiency outputs, recent technological strides show the potential that thin film solar modules provide. In December 2015, the world’s largest CIS solar energy provider, Solar Frontier, set a new record for thin film solar module efficiencies, achieving a 22.3% conversion efficiency [1]. The company aims to achieve 30% soon. What Is Used in Thin film Solar Cells? Thin film solar cells require a very thin layer of PV materials atop an element that absorbs light. Light-absorbing layers commonly include cadmium telluride, copper indium gallium selenide, amorphous silicon, and gallium arsenide. Thin film solar cell materials offer reduced ecological impacts when considering all manufacturing stages compared to crystalline silicon panels [2]. Certain materials involve much more complicated manufacturing than others. For example, permanent applications might require different materials than portable models, and large-scale commercial operations differ greatly from home rooftop needs. Below, we discuss the specific element requirements and manufacturing steps for the most common layering materials. Why Is Thin Film Used in Solar Cells? Developers may opt for a thin film solar panel to reduce costs, use less material, and create less waste. These solar panels are easier to manufacture, reducing time limitations and excessive expenses. You also have more versatility when choosing thin film technologies over the first-generation c-Si option. With the decreased weight and increased flexibility, commercial contractors can apply the cells between window panes or laminate the thin film panel directly on the glass. Additional applications include portable calculators, vehicles, and more. Source: Fieldsken Ken Fields The Different Types of Thin Film Solar Technology Thin film solar panels work well across different materials to meet the needs of various commercial applications. Below, we explain the advantages and disadvantages of each. Cadmium Telluride (CdTe) CdTe panels rely on two absorber layers, p-doped Cadmium Telluride and n-doped CdS, which combine to create a p–n heterojunction. Above this layer, the CdTe cells use fluorine-doped tin oxide and zinc telluride with a paste substrate to form a Transparent Conductive Oxide layer. CdTe technology usually requires either: Vapor-transport deposition Closed-space sublimation deposition The current top efficiency level reached under Standard Testing Conditions using CdTe panels is 19%, which is 3.1% beneath the top single solar cell achievements [3]. Calcium telluride boasts a 5.1% worldwide market share, making it the most widely used material for thin film applications. Copper Indium Gallium Selenide (CIGS) Copper selenide thin film panels use a molybdenum electrode layer over the substrate (usually metal foil or polyimide) with a sputtering process. CIGS thin film manufacturers also rely on a p-n heterojunction, combining a p-doped layer (made of CIGS cells) on top of an electrode. CIGS panels require the formation of a CdS n-doped buffer through a chemical-bath deposition. Copper Indium Gallium Selenide (CIGS) thin film solar cells boasted a record-breaking 23.3% efficiency in 2019, with the theoretical ability to increase efficiency to 33% [4]. Amorphous Silicon (a-Si) Amorphous silicon (a-Si) solar cells use a p-i-n or n-i-p configuration instead of an n-p heterojunction by adding an intrinsic semiconductor. The main design configurations for silicon cells include: Amorphous silicon Microcrystalline silicon tandem cells Polycrystalline silicon on top of a glass surface These a-Si thin film modules don’t offer high efficiencies and cost more than other options, with a maximum efficiency of only 14% [4]. Gallium Arsenide (GaAs) Gallium arsenide thin film cell technology requires more complex manufacturing steps that involve growing the GaAs buffers in Si substrates through different chemical and temperature alterations. Next, manufacturers fabricate the solar cell and bond it to the electrode before assembling the layers. The final top contact layer of Pt/Titanium requires electron beam evaporation. The long and complicated manufacturing process and increased costs make this material less accessible. Considering the maximum 29.1% efficiency, this investment usually only gains attention from larger organisations [4]. Thin Film Solar Panels and Crystalline Silicon Solar Panels Thin film solar panels and crystalline silicon solar panels differ in many ways. Crystalline silicon solar panels are the first generation of solar power technology, while thin film cells are the evolved second generation. Regarding performance, c-Si panels display greater reactivity to temperature variations, showing increased thermal PV losses, making them the better choice for extremely hot climates. Another key difference is the balance between efficiency and cost. Some thin film materials offer a low cost, but the efficiency also drops. GaAs thin film panels might display the best efficiency levels out of all the options, though they’re the most expensive and inaccessible, making them only obtainable for space applications. Crystalline silicon solar panels are popular because they offer an appropriate balance between affordable pricing and efficient results. These panels are usually the most suitable choice for commercial, industrial, utility, and residential needs. When looking to save money on thin film solar panels, residential contractors usually consider one of the cheaper material options, as they require a much lower upfront investment. CdTe offers an excellent balance between cost and efficient results. The Applications of Thin film Solar Panels While c-Si panels hold the largest market share amongst residential and commercial users, thin film solar panels also corner different unique market areas. The most typical applications include portable vehicles, rooftops, and large-scale needs. The following use cases are not the only possible applications; they’re just the most popular. Portable Thin Film Solar Panel Thin film technology weighs less and is much smaller than some other options, making it perfect for portable on-the-go use cases. The most common place we see portable panels is in calculators, though recently, increased developments show more potential opportunities. For example, companies could use portable thin film solar panels in laptops, banks, remote locations, and more. The portable application is one of the most accessible options for individual buyers wishing to purchase low-cost products with solar-powered energy. Rooftop People often install flexible PV modules on top of vehicles, like buses, RVs, boats, and more. Since these solar panels are thinner, installers can apply them to curved surfaces commonly found at the top of vehicles. The panels remain nearly invisible from ground level, so consumers can maintain their cars’ appearances while improving their practicality. Typically, since rooftop applications are quite small and only involve a few panels, anyone can purchase with low upfront investment costs. Large Scale Big organisations also occasionally use thin film solar technology for large-scale purposes. These panels are durable and degrade very slowly, potentially offering a better long-term investment. As the manufacturing process becomes cheaper, some predict this underdog will take over the solar power industry. The best example of large-scale thin film applications is in outer space advancements. The lightweight technology offers ideal temperature and damage resistance for the extreme conditions found in space. Thin Film Solar Cell Final Thoughts We’ve seen enormous strides in solar panel technology in recent years. Today, commercial and residential contractors have many materials to choose from, depending on their budget and application needs. Thin film solar cells may not be the most popular option today, though considering their flexibility, application ranges, and potential efficiencies, they could become the next industry standard. Understanding the physics and science behind how these technologies work is complicated. If you’d like to continue learning about thin films, we invite you to browse through more articles from the Korvus Technology blog. References: [1] Maraun, K., & Yamiya, A. Solar Frontier achieves world record thin film solar cell efficiency: 22.3%. Solar Frontier, 8 December 2015. [2] Pearce, J., & Lau, A. Net Energy Analysis for Sustainable Energy Production From Silicon Based Solar Cells. ASME Digital Collection, 5 January 2009. [3] Romeo, A., & Artegiani, E. CdTe-based thin film solar cells: Past, present and future. Laboratory for Photovoltaics and Solid-State Physics, 18 March 2021. [4] Green, M. A., Dunlop, et al. Solar Cell Efficiency Tables (version 55). Progress in Photovoltaics, 20 December 2019

Written by Matt Clancy Published on May 31, 2024 Applications of Thin Film Coatings in Various Fields Are you curious about the many different thin film applications in today’s world? You may not realise it, but thin films play a starring role in many of the creature comforts we’ve come to rely on in our everyday life, from the mirror in your bathroom to the mobile phone in your pocket. However, thin films aren’t new; instead, they’ve been around for a long time. The earliest documented instances date over 5,000 years ago to the Ancient Egyptians, who gilded statues and artefacts with decorative coatings of gold using a chemi-mechanical technique. At Korvus Technology, we know how critical thin-film technology is to our world. We have over 20 years of experience developing, creating, and installing thin-film deposition systems, supplying a wide range of organisations, brands, universities and research centres. Keep reading to learn more about thin films, including structure, morphology, properties, and applications. A Brief Overview of Thin Film Applications Thin-film measurements can range from a single atom to several micrometres. During the thin-film deposition process, we can deposit a single layer of target material onto the substrate, which can enhance certain physical and chemical properties that aren’t present in bulk materials of the same chemical composition. [1,8] Some example thin-film deposition techniques include chemical vapour deposition (CVD) and physical vapour deposition (PVD). [5] PVD involves vaporising the target material, which condenses on the substrate surface, forming a deposited film. PVD deposition techniques include a thermal evaporation process (aka vacuum evaporation), sputtering, and ion plating. [5] CVD triggers a chemical reaction, creating a thin target material layer on the substrate surface. Standard methods include spin coating, laser CVD, and thermal CVD. [5] CVD and PVD methods require complex equipment — i.e., a deposition system with a vacuum chamber. Thin Film Morphology and Structure Thin-film microstructure and properties depend on the growth mechanism, deposition parameters (i.e., low temperature or vapour pressure) and techniques we employ during the manufacturing process. Microstructures consist of three types: Amorphous: Forms a lattice that lacks long-range crystalline structures Polycrystalline: Forms nano/micro crystallites of varying sizes Epitaxial thin films: Forms solid crystalline film with latticework [1] Thin film applications depend heavily on thin-film morphology, and that depends on various factors. It includes deposition techniques and atom adsorption during film growth. Also, the type of material and the flux of vapour and atoms impact the final morphology, growth structure, and film thickness. For example, thin films grown via vapour deposition often feature cylindrical structures. [1] Properties of Thin Films There are several properties that are crucial for modern thin film applications. The manufacturing process must observe certain conditions and take certain precautions, so it’s not harming the thin film applications afterwards. When depositing thin films onto a substrate, essential considerations include characterisation techniques and long-term performance of the enhanced properties. Thin-film coatings behave differently from bulk material, and residual stress during deposition can alter the film’s properties, like causing defects in the crystalline structure or epitaxial growth. [1,4] Such stressors and the film’s microstructure can negatively affect its mechanical properties, like hardness and yield. [3] Substrate and film type (i.e., metallic films, insulators, semiconductors), purity, and scaling alter electrical properties, such as reducing conductivity. [4] Finally, the connection between deposition parameters and microstructure growths influences a thin film’s optical properties. [1] Applications of Thin Film Technology in Various Industries Thin-film technologies are prevalent in virtually every industrial sector. For example, this technology is essential for fabricating active and passive devices, complex optical systems, and even protective coatings for tools. Read on as we explore nine typical thin film applications, including thin film batteries, optics, magnetics, resistors, solar cells, and many more. Thin-Film Interference Applications Among the modern thin film applications, thin film interference is often one of the first that comes to mind. Thin-film interference is an optical illusion caused by the interaction and reflection of light on the top and bottom surfaces of a film [3]. This phenomenon occurs when a light ray partially reflects off the surface of a thin film. The remaining light passes through, reflecting off the film’s bottom and then interfering with the first ray on the top. [3] The most common application of thin-film interference is optical devices, including lenses and mirrors. It’s also present on the wings of certain butterflies, on soap bubbles, and as a security feature on money, credit cards, driver’s licenses, etc. [3] Zinc Oxide-Based Thin-Film Applications ZnO thin film applications (zinc oxide) are commonplace in several industries and devices, including thermal, optical, magnetic, and electrical. However, primary uses of ZnO thin films include semiconductor devices and coatings. [8] ZnO films are also suitable for these applications: Displays Solar cells LED OLED Gas sensors Lasers Biosensors Photodetectors ZnO is also physically and chemically stable, readily available, inexpensive, and has excellent conductivity. For those reasons, it’s a popular alternative to other materials in the thin film sector, like indium tin oxide or gallium nitride. [8] Thin Film Resistor Applications Thin-film resistors are widespread in modern technology and crucial among thin film applications. Its applications range from radio receivers and circuit boards to computers and radiofrequency devices. Additional applications include monitors, wireless routers, Bluetooth modules, cell phone receivers, and electronics, where they’re invaluable. For example, nickel-chromium alloy-embedded resistors are vital for manufacturing smaller, thinner electronic devices due to their high resistivity [9]. Researchers discovered that embedding these resistors into a printed wiring board improves electrical performance and reliability while increasing device functionality. They can also enhance temperature stability by infusing the alloy with small amounts of aluminium and silicon [9]. Magnetic Thin Film Applications Magnetic thin films are essential components of many devices, including electronics, data storage, radio-frequency identification, microwave devices, displays, circuit boards, and optoelectronics. Beyond that, they’re critical for fabricating wearable electronics, including biomedical sensors. By far, this is one of the most common uses that drive thin film applications to be so important. [7] Magnetic films are ideal for use in those industries due to their lightweight, portable size, flexible substrates, and biocompatibility. These properties make them highly suitable for photonic, spintronic, and recording devices. [7] Sensors containing magnetic films that use a flexible substrate (instead of a flat substrate) during deposition may even have the potential to detect the magnetic field of living organisms. [7] Optical Coating Optical thin films have firm roots in today’s modern technologies. Standard applications include optical coatings and optoelectronics, which have an impressive range of uses. For example, manufacturers can create optoelectronic thin-film chips (semiconductors) using molecular beam epitaxy. MBE involves depositing a single atom at a time onto the substrate to create epitaxial films. [1,5,6] A highly pure, high vacuum environment is necessary to fabricate optical coatings due to the negative effect impurities can incur in any film, these coatings have numerous uses, including lenses (i.e., glasses, telescopes) and mirrors. The coating itself affects how the optics reflect and convey light; for example, we can create anti-reflective coatings or the opposite, highly reflective coatings. [6] Polymer Thin Film Applications Applications for polymer thin films range from solar cells and electronics to healthcare and memory chips. Advancements in chemical deposition methods (CVD) allow greater control over polymer film coatings, including coating thickness and conformity. Certain chemical reactions allow for solvent-free fabrication, eliminating the risk of adverse reactions to human tissue. [2] Now, there are “smart membranes,” which change permeability or selectivity based on environmental stimuli, like low temperatures, very low pressures or pH changes. [2] These polymer thin film coatings have many biomedical applications, including drug delivery systems, tissue engineering and biosensor creation. [1] Thin-Film Battery Applications Have you ever heard of a lithium-ion battery? These rechargeable batteries power many of the world’s mobile phones and laptops. The technology has grown exponentially in the last decade, but the integration of thin films has advanced it further than ever before. Now, thin-film batteries are the superior choice over lithium-ion. They’re thinner, lighter, and denser without sacrificing voltage or current. [6] Their narrower proportions are ideal for use in complex electronics, like ultra-thin laptops. Another application for thin-film batteries is in the healthcare industry, where they power implantable medical devices. [6] Thin-Film Coating Applications Thin-film coatings provide many practical uses in various industries and technologies. During deposition, manufacturers use coating techniques to improve the chemical and mechanical properties of target materials. Common examples include anti-reflective coatings, anti-ultraviolet or infrared coatings, anti-scratch coatings, and lens polarisation. [1] Additional uses for film coatings include: Anti-corrosion coatings: Reduce rust and degradation in pipes, engine parts, bearings, etc. Hard coatings: Increase the durability of cutting tools while reducing friction Architectural glazing: Improve energy efficiency and lower utility costs in offices and skyscrapers [1] Thin-Film Solar Cells Applications Thin-film solar cells are invaluable to the solar energy sector, providing clean, low-cost energy generation. The two primary technologies are thermal energy and photovoltaic systems. [1] At first, solar cell technology used amorphous silicon thin films. However, now the standard is copper indium gallium selenide, which has greater stability and higher efficiency (around 23%). [1] Thin-film solar cells are also prevalent in the solar energy sector because their absorber layer has a high absorption coefficient. That allows for a considerable reduction in cost and material thickness while increasing conversion efficiency. [1] Final Thoughts on Thin Film Applications Thin-film applications are so numerous in everyday life that it would be difficult to find an industry that doesn’t rely on this advanced technology. They have practical uses in almost every sector, from healthcare and memory chips to electronics and solar energy. At Korvus Technology, we have a broad customer base of global brands and organisations that rely on our innovative solutions, including thin-film deposition systems, accessories, and instruments. Do you want to learn even more? Keep browsing the Korvus Technology website to read additional informative blog posts about this fascinating technology. References [1] Acosta, E., & Ares, A. E. (2021). Thin Films/Properties and Applications (Revised ed.). https://doi.org/10.5772/intechopen.87838 [2] Khlyustova, A., Cheng, Y., & Yang, R. (2020). Vapor-deposited functional polymer thin films in biological applications. Journal of materials chemistry. B, 8(31), 6588–6609. https://doi.org/10.1039/d0tb00681e [3] Ling, S. J., Sanny, J., & Moebs, W. (n.d.). University Physics (Vol. 3). Rice University. https://opentextbc.ca/universityphysicsv3openstax/front-matter/preface/ [4] Ohring, M. (2002). Materials Science of Thin Films. Elsevier Gezondheidszorg. https://www.sciencedirect.com/book/9780125249751/materials-science-of-thin-films [5] Oluwatosin Abegunde, O., Titilayo Akinlabi, E., Philip Oladijo, O., Akinlabi, S., & Uchenna Ude, A. (2019). Overview of thin film deposition techniques. AIMS Materials Science, 6(2), 174–199. https://doi.org/10.3934/matersci.2019.2.174 [6] Rao, M. C., & Shekhawat, M. S. (2013). A Brief Survey on Basic Properties of Thin Films for Device Application. World Scientific. Retrieved March 18, 2022, from https://www.worldscientific.com/doi/pdf/10.1142/S2010194513010696 [7] Sheng, Ping & Wang, Baomin & Li, Runwei. (2018). Flexible magnetic thin films and devices. Journal of Semiconductors. 39. https://iopscience.iop.org/article/10.1088/1674-4926/39/1/011006 [8] Vyas, S. (2020). A Short Review on Properties and Applications of Zinc Oxide Based Thin Films and Devices : ZnO as a promising material for applications in electronics, optoelectronics, biomedical and sensors. Johnson Matthey Technology Review, 64(2), 202–218. https://doi.org/10.1595/205651320×15694993568524 [9] Wang, J., & Clouser, S. (2001). Thin film embedded resistors. Ticer Technologies Publication, pp.1-6. https://ticertechnologies.com/wp-content/uploads/2015/12/01_ThinFilm.pdfcom

Written by Matt Clancy Published on December 12, 2022 PVD in the Development of Solid-State Thin-Film Batteries Physical vapour deposition (PVD) is an emerging technology that improves the manufacturing process for batteries, including lithium batteries as an alternative to lithium-ion batteries in modern electronics. A solid-state thin-film battery can be safer, smaller, and less expensive. However, the batteries depend on films that can be less than a micron thick, made of highly purified materials, making them dependent on innovative technologies based on PVD. The manufacture of thin-film batteries depends on scarce materials such as lithium. Loss of raw materials during the process adds to the cost of batteries and other electronic components. Physical vapour deposition is one of many revolutionary technologies that streamline manufacturing across numerous industries and applications. This article will break down the use of PVD in the development of solid-state batteries. What Is a Solid-State Battery? A solid-state thin-film battery is a storage device for electrical energy. Unlike older technologies based on liquid materials, such as lead-acid batteries and lithium-ion batteries, a solid-state battery uses different battery chemistries, electrolyte materials, conductive materials, and other components. Batteries containing liquid electrolytes can leak, lose their ability to retain charge, develop a loss of cycling stability, suffer electrolyte leakage, function poorly at low temperatures and cause damage and harm when they malfunction. A lithium-ion battery also cannot match the high energy density and power density of thin-film batteries. Solid-state batteries, on the other hand, use solid electrolytes that avoid safety concerns and performance issues that limit the usability of earlier battery technologies, such as lithium-ion batteries. These batteries consist of layers of materials, such as lithium. As with older batteries, materials lose or accept electrons, allowing the flow of electrical energy when the battery discharges or takes on a charge. Barrier layers in thin-film batteries control the movement of electrons and prevent the battery from short-circuiting. The solidity and flexible polymers of thin-film batteries give engineers more design options for portable electronics, where optimal use of space is crucial. How Are Thin-Film Batteries Made Using PVD? PVD and solid-state batteries involve creating layers of conductors, insulators, and electrolytes that perform crucial roles in the battery. PVD allows the manufacturer to use different techniques for each layer without disrupting existing layers. What is PVD? PVD stands for physical vapour deposition: the process manufacturers use to create a thin layer of a material. PVD technology reduces waste and increases the purity of lithium layers in the thin-film battery. During the PVD process, the material is converted into a gas and directed toward the substrate. The material deposits on the substrate at a rate of one or more nanometres per second. Manufacturers have precise control over the thickness of the deposition layer and achieve higher energy densities and electrochemical performance. With PVD, manufacturers can create layers that are pure and strong. This can help reduce the size and weight of the created batteries – an essential feature of modern battery manufacturing. The precision of PVD allows for 3D-printed batteries that manufacturers integrate into smart cards and power supply components. The high electrochemical performances of PVD layers and their versatility make thin-film deposition important for developing Internet of Things (IoT) devices with thin-film batteries. The Physical Vapour Deposition Process in the Development of Thin-Film Batteries Several techniques for thin-film deposition exist. [1] One common manufacturing process involving PVD for thin-film batteries is thermal evaporation. Thermal evaporation involves placing the material in a vacuum chamber, heating the material until it evaporates, and sending the resulting plume of vapour toward the material that it will eventually coat. The process is most effective when the material melts and evaporates easily. A high vacuum will improve the process by reducing the concentration of impurities in the thin films. Unlike chemical vapour deposition, which requires a high temperature of over 1,000 degrees centigrade, PVD occurs at a few hundred degrees centigrade. Deposition at low temperatures can be beneficial if a high substrate temperature could damage other battery layers during construction. Thermal evaporation is not the only PVD coating process. Other techniques create thin coatings without generating too much heat. Pulsed laser deposition (PLD) uses a laser beam to vaporize the material. Manufacturers can precisely control the delivery of energy to the material. PLD makes the transfer process more effective and reduces the lithium needed to make the film. Magnetron sputtering [2] creates a plasma of inert gas [3] and uses the ions to disrupt the coating material, spraying it onto the substrate and creating a uniform film across the wafer. Understanding thin-film materials gives manufacturers options in developing a manufacturing process that produces batteries to meet performance standards and constraints for specific applications. What Materials Go Into Making Solid-State Thin-Film Batteries With PVD? Batteries generate current by transferring electrical current between the electrodes, from the anode materials to the cathode materials. Anode materials: A thin film of metallic lithium is the typical anode material for its safety and high negative electrochemical potential. Cathode materials: Lithium oxides such as lithium Ion Phosphate (LFP or LiFePO4), NCM, or other materials with crystalline surface morphologies. The crystal structure of the cathode material facilitates Li-ion transportation (movement of lithium ions). The anode and cathode electrode materials each connect to a current collector. The current collectors let electric current flow out of the battery into the device’s electric circuitry. The purity of PVD cathodes gives lithium battery thin-film models excellent electrochemical performance for high-power applications. A physical separation interface (an electrical insulator) prevents the anode and cathode from touching and short-circuiting the battery. The barrier serves as a solid electrolyte, such as LiPON or related compounds with high conductivity of lithium ions, despite its low electronic conductivity. The barrier consists of a polymer such as a polyether, vinyl alcohol, or polycarbonates, or an efficient ion conductor, good electrical insulator, and solid-state electrolyte interface [4], such as: Lithium lanthanum zinc oxide Lithium lanthanum titanium oxide Lithium phosphorus oxynitride Polyanionic oxides Sulfides The active material component for a thin-film lithium battery depends on the desired electrical performance, nominal voltage, initial capacity, ionic conductivity, and other factors that influence battery performance. How Korvus Technology Can Help Korvus Technology can help you move past li-ion batteries and liquid electrolyte technology and benefit from increased chemical stability, capacity, higher energy density, faster recharge times, and higher average output voltage. Take advantage of ongoing improvements to solid-state batteries’ chemical, electrochemical, mechanical, and thermal stability. [5] At Korvus Technology, we’ve created the HEX thin film deposition system; a system suited to the thin-film lithium batteries and other renewable energy storage devices for wireless sensors, radio frequency identification tags, medical devices, electron microscopy, rechargeable batteries and other thin-film battery applications. Contact us to explore our range of modular PVD systems. References [1] Boone, D. H. (2013). Physical vapour deposition processes. Materials Science and Technology, (2)3 220-224. [2] Baptista, A., F. J. G., Silva, J. Porteiro, J. L. Míguez, G. Pinto, & L. Fernandes. (2018). On the physical vapour deposition (PVD): Evolution of magnetron sputtering processes for industrial applications. Procedia Manufacturing, (17) 746-757. [3] Schneider, J., S. Rohde, W. D. Sproul, & A. Matthews. (2000). Recent developments in plasma assisted physical vapour deposition. Journal of Physics D: Applied Physics, 33(18), R173. [4] Xiao, Y., Y. Wang, S.-H. Bo, J. C. Kim, L. J. Miara & G. Ceder. (2020). Understanding interface stability in solid-state batteries. Nature Reviews Materials, 5, 105-126. [5] Chen, R., Q. Li, X. Yu, L. Chen, & H. Li. (2019). Approaching practically accessible solid-state batteries: stability issues related to solid electrolytes and interfaces. Chemical Reviews, 120(14), 6820–6877.

Written by Korvus Technology Published on February 9, 2022 What Is PVD Coating? Physical Vapour Deposition Explained The need for high-performance thin-film coatings is higher today than ever, and many industries have turned to physical vapour deposition (PVD) as their coating method of choice. PVD is the gold standard for generating extremely thin, pure, and durable coatings from a wide array of target materials and substrates to coat everything from optics to computer chips. What Is the PVD Coating Process? PVD coating, also known as thin-film coating, uses a vacuum chamber to vaporise a solid material and deposit it onto a target substrate, atom by atom. The result is an extremely thin, extremely pure coating from a technique that is more environmentally friendly than many other coating technologies[1]. The PVD coating process occurs under vacuum conditions and consists of four main steps: ablation, transport, reaction, and deposition. This process deposits source atoms onto the surface of the substrate, leaving it coated with a strong, abrasion- and corrosion-resistant film. Evaporation The two main types of physical vapour deposition are Sputtering and Thermal Deposition. Thermal evaporation deposition uses vacuum pressures and high temperatures to create the conditions necessary for the vaporisation of the target material. Sputtering uses a high-vacuum chamber that dislodges atoms from the target using high-energy plasmas. These atoms are then ready for deposit onto the target surface, usually in a plasma arc. This process biases the target before bombarding it with ionised gas in a vacuum environment. This ionic bombardment results in atoms “sputtering” off the target into a plasma cloud arc before transport and condensation. Both processes have unique advantages and disadvantages that make them useful for different applications. Sputtering produces a highly uniform coating with low impurity rates, but it is also the slowest and most complex method. Thermal evaporation has higher throughput and high mineral utilisation efficiency but may require additional tools to achieve good uniformity during the process, such as sample rotation[2]. Transportation The movement of vaporised atoms from the target material to the substrate requires precise timing and positioning. The correct PVD method for the material is important as well as the geometry of the system and deposition source in relation to the sample holder. Reaction PVD processes can use reactive or inert gases to produce a strong bond between the coating and the substrate for the best possible results. For example, oxygen and nitrogen are common gases used for reactive RF sputtering with metal oxides and nitrides. Deposition The final step of the process builds up the coating on the required substrate. Since the thin-film can be anywhere from a few atoms thick up to a few microns, a uniform deposition across the substrate is important. The PVD process involves rotating the substrate at a constant speed while monitoring the rate of deposition with other tools such as a quartz crystal microbalance. Many industrial methodologies can automate the deposition process by putting a conveyor belt of targets in front of the vaporised arc for a certain length of time. Both sputtering and evaporation can use automation to speed up the PVD coating technique for mass production. Safety, Properties, and Advantages of PVD Coatings Advantages of PVD Coatings Safer than Plating PVD coating is an alternative to traditional metal coating processes, where a thin layer of metal coats a substrate. In industry, metal coating processes use either an electric current (electroplating) or an autocatalytic process (electroless plating) to achieve a strong bond between the substrate and metal. However, many traditional coating processes also produce potentially harmful waste products, and some processes such as cadmium coating are decreasing in popularity due to safety concerns[3]. PVD coating requires no compounds other than the substrate and target material, resulting in a more environmentally friendly, safe process that caters to a wide range of industries and applications. Highly Durable PVD coatings tend to have highly robust temperature tolerance and impact strength along with excellent abrasion and corrosion resistance[4]. Versatile Unlike metal plating, PVD is suitable for almost any inorganic coating material over a massive range of substrates. Manufacturers can use different PVD technology to generate a wide range of finishes ideal for almost any application or part. Is PVD Coating Food-Safe? PVD coatings vary dramatically in their chemical properties, but most adhere strongly to their substrate once applied and are often chemically and biologically inert. One of PVD’s most prominent industries is the cutlery industry for both decorative and functional applications, including commercial kitchen equipment. Most PVD finishes are food-safe and provide wear-resistant coatings that can withstand significant wear and tear[5]. PVD Applications Across Industries PVD’s versatility in materials, finish, and composition makes it an appealing coating choice for a vast array of industries. Wherever you find a coated material, you’ll likely find a PVD process behind it. Microelectronics Electronics like phones, circuits, and optical discs have a thin film deposited on them for conductivity and durability. Some films can act like superconductors and enhance the performance of electronic semiconductor devices. Home Hardware Many home fixtures, including taps, sinks, showerheads, window dressings, and drawer handles, use a vacuum coating of various materials, including nickel, stainless steel, copper, bronze, and even black PVD coatings. PVD coatings are also commonly used in interior fixtures such as valves that experience high wear and tear. When coated with robust materials, these fittings can last significantly longer than with traditional chemical coating methods. Automotive Applications Many automotive parts use chrome as a decorative and functional coating, including interior trim, engine components, and even headlamps. PVD coatings allow for a more durable product that uses cleaner technology with PVD coating equipment instead of messy tanks of electrolytes. PVD coating stainless steel creates less friction and higher temperature tolerances, essential to getting the best performance out of engine components. Plastic headlights contain a thin metal coating of aluminium to create a mirror to reflect the light generated from the LED bulb. Food Packaging Aluminium is an often-used preservative in the food industry, but the hardness and rigidity make it unsuitable for some packing applications. Aluminium-coated plastic is a common package for crisps and other snack foods to keep them fresher for longer. Another application is to embed silver in existing PET plastics to prevent microbial growth[6]. This method will ensure that the plastic retains its bulk properties while providing food safety advantages. Optics Modern eyewear uses plastic lenses that are more durable than their glass counterparts but are more prone to scratching and discolouration. A PVD coating retains the hardness and versatility of plastic while adding an anti-reflective or scratch-resistant layer for maximum durability. Several car manufacturers also use a PVD coating machine to tint car windows or apply a UV-resistant film. This film ensures that drivers still get maximum visibility due to the finish of the product while getting the benefits of UV protection and privacy. PVD coating are also implemented in research of future photovoltaic applications and other transparent conducting oxide applications. Medicine PVD films are essential components in the medical field, with an extensive range of applications. A popular PVD coating, titanium nitride, is a standard coating on prosthetics, whose metals the host body often rejects due to interaction with biological liquids. It’s also useful as a surface coating for scalpels as it helps blades retain their sharpness longer. Chromium nitride is a standard thin film for orthopaedic and dental instruments requiring regular sterilisation with high-pressure, high-temperature autoclaves. The film protects the tool’s surface from wear and corrosion, leading to improved performance and cost-effectiveness of the tools. Home Tools Many stainless steel home tools have coatings to keep their edges sharper for longer. Some of the most common finishes and PVD films include titanium nitride and diamond-like coatings that are significantly harder than steel. These films keep drill bits and other tools sharper, which is essential for high-pressure applications. Decorative Applications PVD is appealing for decorative use due to its variety and range of both colours and finishes, as well as its versatility in materials. These include copper PVD coating, nickel or chrome coatings, or even ceramic films. Compared to traditional methods of metal finishing, PVD increases hardness and resistance to tarnishing and fading. A designer can limit its application to one part or use it on multiple components. Common usages are knives and blades, fittings, and even jewellery. What Are the Most Common PVD Coating Target Materials? Evaporative and sputtered PVD coatings are suitable for almost any inorganic solid material and almost any target surface. Materials with a high melting and vaporisation temperature will do better with sputtering in the vacuum chamber instead of evaporation techniques. However, there is a process suitable for almost any material or product on the market. Some common materials for sputtering films include: Cr2N: A beautiful silver film used to PVD-coat external parts of watches or jewellery TiN: One of the most-used sputtering films, useful in decorating phones, glasses, hardware parts, and sanitary ware ZnSn: An optical PVD coating that reflects light, leading to its use in low-e windows and glass AlCr: A sputtering film that extends the service life of equipment like tools and machine parts ITO thin film: A high-conductivity, high-mechanical-hardness film useful for LCDs, plasma displays, and touch panels Different industries will have varying requirements for their PVD material films, with distinct coatings suitable to those requirements. However, some popular compounds make it into a huge range of industries due to their well-documented, universally useful properties. Conclusion Korvus Technology is a leading materials science research and development company in the UK with extensive industrial experience in thin-film technology and high-vacuum PVD coatings. We manufacture the HEX Series, a thin film deposition system that provides support for a variety of techniques, depending on your requirements. Interested in learning more? We’d be happy to speak with you and understand your project and how our HEX system can help. References [1] P. De Araujo, P. Steyer, J.-P. Millet, E. Damond, B. Stauder & P. Jacquot (2003). PVD Aluminium Alloy Coatings: Environmentally Friendly Alternative to Protect Steel Parts Against Corrosion, Surface Engineering, 19:4, 304-309, DOI: 10.1179/026708403322499245 [2] O. Kahveci, A. Akkaya, E. Ayyildiz & A. Turut (2017). Comparison of the Ti/n-GaAs Schottky Contact’s Parameters Fabricated Using DC Megatron Sputtering and Thermal Evaporation. Surface Review and Letters 04:24. DOI: 10.1142/S0218625X17500470 [3] World Health Organization. Exposure to Cadmium: A Major Public Health Concern. https://apps.who.int/iris/bitstream/handle/10665/329480/WHO-CED-PHE-EPE-19.4.3-eng.pdf, Accessed 03 February 2022. [4] J. Smolik, M. Gulde, J. Walkowicz & J. Suchanek (2004). Influence of the structure of the composite: ‘nitrided layer/PVD coating’ on the durability of forging dies made of steel DIN-1.2367. Surface and Coatings Technology 180-181, 506-511. DOI: 10.1016/j.surfcoat.2003.10.152 [5] P.Eh. Hovsepian, W.-D. Münz, A. Medlock, & G. Gregory (2000). Combined cathodic arc/unbalanced magnetron grown CrN/NbN superlattice coatings for applications in the cutlery industry. Surface and Coatings Technology 133-134, 508-516. DOI: 10.1016/S0257-8972(00)00921-X [6] M. Benelmekki, M. Torrell, E. Xuriguera, F. Vaz, & V. Teixeira (2012). Structure and Properties of Silver Clustered Implanted in PET by PVD Stuttering for Active Packaging Applications. Journal of Nano Research 18-19, 105-116. DOI: 10.4028/www.scientific.net/JNanoR.18-19.105