Preparation and properties of GaP films on ZnS substrate

By using Radio Frequency and Plasma Enhanced Chemical Vapor Deposition(RF-PECVD), GaP film is fabricated on ZnS substrate. Under low load condition, the film features Vickers hardness of 750kgf/mm²and film thickness of 10μm. With designed and fabricated DLC/GaP/ZnS film system on ZnS substrate with thickness of 4.2mm, the average transmittance in the bandwidth 8~12μm reached 80.4%. It is indicated by the study of deposition rate of GaP film, optical and mechanical properties and anti-rain erosion and anti-sand erosion that the film growing rate will be faster with the increase of RF power and the deposition rate will be decreased because of the increase of substrate temperature, so it is as the lab atmospheric pressure increase. However , it has more defects in films with the increase of RF power and this results in more absorption, reflection and scattering in the IR transmittance. The higher lab atmospheric pressure and vacuum is, the less impurity in the deposited film will be. GaP film has the ability of protecting ZnS substrate from rain erosion and this ability increases by the thickness of film. And the combination of DLC and GaP has excellent property in anti-sand erosion.