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Physical Vapor Deposition Of Thin Film

PVD or physical vapor deposition is a method with the help of which a thin film of material is coated on a substrate by following certain steps. First, the material which is to be deposited is changed to vapor with the help of physical means. It is then transported to a region of low pressure from the substrate. Then, it undergoes condensation on the substrate to form the thin film.

Physical vapor deposition and thin film deposition methods are clean and the coating is deposited over the entire object at the same time rather than going for localized regions. All of these processes combine a method for deposition of the material, combination with an active gas like oxygen, nitrogen or methane and plasma bombardment of the substrate to make a hard coating. The methods in PVD differ in the means for producing the metal gas and the way plasma is created. The main PVD methods are ion manipulation, laser surface alloying, plating and spluttering.

PVD has many classes of vacuum coating processes in which the material is physically removed from a source of sputtering or evaporation and then transported through vacuum by the energy of the particles of the vapor. It is then condensed as a film on the surfaces of appropriately placed substrates. In case of chemical compounds, they are deposited by adding a reactive gas which contains desired reactants that react with metal from the PVD source or by using a similar source material.

Over the last few years, many PVD processes have evolved. They are recognized by many names. Most of them are named after the physical gas source like radio frequency sputtering, diode or triode sputtering, electron beam evaporation, planar or cylindrical magnetron sputtering, arc evaporation and activated reactive evaporation.

Despite of all the names they are given, they can broadly be categorized under three phases namely emission from a source, condensation on substrates to be coated and transport in vacuum.

Usually, PVD processes have been relatively costly due to expensive vacuum equipment, slow deposition rates and throughput limitations. Recently, the use of PVD methods have increased a lot due to decreased costs and increased demand for high performance materials and coatings.

PVD is a good coating process for hard coatings. Although it requires more parts preparation, greater processing time, more expensive equipment and more system maintenance as compared to other processes, it is all worth it when it comes to the end product. At times, it is the only method that is capable of depositing a coating of the desired material. When all the factors are considered, the overall cost of PVD can be quite less than other coating processes.