Physical Vapour Deposition or PVD is a general term for deposition of a thin film of metallic material on surfaces, eg. coating of semiconductor devices and aluminised PET film for snack bags. The method is an entirely physical process using techniques such as high temperature vacuum evaporation or plasma sputter bombardment instead of chemical reaction at the surface. Sputter deposition has become one of the most popular PVD methods. In this case, the sputtering gas ions, typically inert argon, krypton or xenon, form ions as sputter atoms from a target. The target atoms then condense on the substrate to form a thin film.