Abstract

Thermally evaporated ZnS forms dense polycrystalline films which exhibit compressive stress that may lead to structural failure of thicker samples. However, we have observed that ZnS films deposited onto liquid nitrogen cooled substrates are amorphous and exhibit tensile stress and lower refractive indices. The last two factors indicate that the cooled films have a lower density than conventionally deposited films. Ion assisted deposition (IAD) can be used to densify a film which leads to increased compressive stress. We have investigated the possibility of tuning the stress within a ZnS film by using IAD in conjunction with substrate cooling, with the goal of improving the structural stability of thicker ZnS coatings.

© 1988 Optical Society of America