Vacuum Coating
Vacuum deposition is a group of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes operate at pressures well below atmospheric pressure (i.e., vacuum). The deposited layers can range from a thickness of one atom up to millimeters, forming freestanding structures. Multiple layers of different materials can be used, for example to form optical coatings. The process can be qualified based on the vapor source; physical vapor deposition uses a liquid or solid source and chemical vapor deposition uses a chemical vapor. Description The vacuum environment may serve one or more purposes: * reducing the particle density so that the mean free path for collision is long * reducing the particle density of undesirable atoms and molecules (contaminants) * providing a low pressure plasma environment * providing a means for controlling gas and vapor composition * providing a means for mass flow control into the processing chambe ...
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