Physical vapor deposition

Physical vapor deposition (PVD) is a variety of vacuum deposition and is a general term used to describe any of a variety of methods to deposit thin films by the condensation of a vaporized form of the material onto various surfaces (e.g., onto semiconductor wafers). The coating method involves purely physical processes such as high temperature vacuum evaporation or plasma sputter bombardment rather than involving a chemical reaction at the surface to be coated as in chemical vapor deposition. The term physical vapor deposition appears originally in the 1966 book “Vapor deposition” by CF Powell, JH Oxley and JM Blocher Jr, but Michael Faraday was using PVD to deposit coatings as far back as 1838.

[
thumb|320px|Molecular dynamics computer simulation of the basic physical process underlying physical vapour deposition: a single Cu atom deposited on a Cu surface.]

Variants of PVD include, in order of increasing novelty:
*Evaporative deposition - In which the material to be deposited is heated to a high vapor pressure by electrically resistive heating in "low" vacuum.
*Electron beam physical vapor deposition - In which the material to be deposited is heated to a high vapor pressure by electron bombardment in "high" vacuum.
*Sputter deposition - In which a glow plasma discharge (usually localized around the "target" by a magnet) bombards the material sputtering some away as a vapor.
*Cathodic Arc Deposition - In which a high power arc directed at the target material blasts away some into a vapor.
*Pulsed laser deposition - In which a high power laser ablates material from the target into a vapor.

PVD is used in the manufacture of items including semiconductor devices, aluminized PET film for balloons and snack bags, and coated cutting tools for metalworking. Besides PVD tools for fabrication special smaller tools mainly for scientific purposes have been developed. They mainly serve the purpose of extreme thin films like atomic layers and are used mostly for small substrates. A good example are mini e-beam evaporators which can deposit monolayers of virtually all materials with melting points up to 3500°C.

Some of the techniques used to measure the physical properties of PVD coatings are:
*Calo tester - coating thickness test
*Scratch tester - coating adhesion test
*Pin on disc tester - wear and friction coefficient test

See thin-film deposition for a more general discussion of this class of manufacturing technique.

Body jewellery

Physical vapor deposition is often used to produce black implant-grade, autoclavable body jewellery. Biocompatible titanium coating is vaporized in an arc then electrically deposited on stainless steel jewellery.

External links

* [http://www.svc.org/ Society of Vacuum Coaters]