Behavior of Three Types of Plasma Sources for Optical Coating

Typical plasma sources, as used in optical coating, bombard the surfaces of the substrates with electrons and ionized gasses such as argon, oxygen, and nitrogen. The energy of the ions in electron volts and the ion current depend primarily on the source geometry, gas flow, pumping speed of the chamber, and the current provided by the power supplies to the ion source and electron source. Three common types of such sources with differing geometries are compared over their practical ranges of operation in various optical coating production chambers. Some aspects of using plasma assisted deposition to influence coating properties such as density, absorption, microscopic structure, adhesion, hardness, etc., are touched upon. The probable benefits of the various source geometries for different applications are mentioned.