Physical vapor deposition

Comparison to other deposition techniques

Advantages

• PVD coatings are sometimes harder and more corrosion-resistant than coatings applied by electroplating processes. Most coatings have high temperature and good impact strength, excellent abrasion resistance and are so durable that protective topcoats are rarely necessary.
• PVD coatings have the ability to utilize virtually any type of inorganic and some organic coating materials on an equally diverse group of substrates and surfaces using a wide variety of finishes.
• PVD processes are often more environmentally friendly than traditional coating processes such as electroplating and painting.
• More than one technique can be used to deposit a given film.
• PVD can be performed at lower temperatures compared to chemical vapor deposition (CVD) and other thermal processes. This makes it suitable for coating temperature-sensitive substrates, such as plastics and certain metals, without causing damage or deformation.
• PVD technologies can be scaled from small laboratory setups to large industrial systems, offering flexibility for different production volumes and sizes. This scalability makes it accessible for both research and commercial applications.

Disadvantages

• Specific technologies can impose constraints; for example, the line-of-sight transfer is typical of most PVD coating techniques, however, some methods allow full coverage of complex geometries.
• Some PVD technologies operate at high temperatures and vacuums, requiring special attention by operating personnel and sometimes a cooling water system to dissipate large heat loads.

Applications

Anisotropic glasses

PVD can be used as an application to make anisotropic glasses of low molecular weight for organic semiconductors. The parameter needed to allow the formation of this type of glass is molecular mobility and anisotropic structure at the free surface of the glass. The configuration of the polymer is important where it needs to be positioned in a lower energy state before the added molecules bury the material through a deposition. This process of adding molecules to the structure starts to equilibrate and gain mass and bulk out to have more kinetic stability. The packing of molecules here through PVD is face-on, meaning not at the long tail end, allows further overlap of pi orbitals as well which also increases the stability of added molecules and the bonds. The orientation of these added materials is dependent mainly on temperature for when molecules will be deposited or extracted from the molecule. The equilibration of the molecules is what provides the glass with its anisotropic characteristics. The anisotropy of these glasses is valuable as it allows a higher charge carrier mobility. This process of packing in glass in an anisotropic way is valuable due to its versatility and the fact that glass provides added benefits beyond crystals, such as homogeneity and flexibility of composition.

Decorative applications

By varying the composition and duration of the process, a range of colors can be produced by PVD on stainless steel. The resulting colored stainless steel product can appear as brass, bronze, and other metals or alloys. This PVD-colored stainless steel can be used as exterior cladding for buildings and structures, such as the Vessel sculpture in New York City and The Bund in Shanghai. It is also used for interior hardware, paneling, and fixtures, and is even used on some consumer electronics, like the Space Gray and Gold finishes of the iPhone and Apple Watch.

Cutting tools

PVD is used to enhance the wear resistance of steel cutting tools' surfaces and decrease the risk of adhesion and sticking between tools and a workpiece. This includes tools used in metalworking or plastic injection molding. The coating is typically a thin ceramic layer less than 4 μm that has very high hardness and low friction. It is necessary to have high hardness of workpieces to ensure dimensional stability of coating to avoid brittling. It is possible to combine PVD with a plasma nitriding treatment of steel to increase the load bearing capacity of the coating. Chromium nitride (CrN), titanium nitride (TiN), and titanium carbonitride (TiCN) may be used for PVD coating for plastic molding dies.

Other applications

PVD coatings are generally used to improve hardness, increase wear resistance, and prevent oxidation. They can also be used for aesthetic purposes. Thus, such coatings are used in a wide range of applications, such as:

• Aerospace industry
• Architectural ironmongery, panels, and sheets
• Automotive industry
• Dyes and molds
• Firearms
• Optics
• Watches
• Jewelry