Influence of Substrate Temperature on the Condensation of Vacuum Evaporated Films of MgF2 and ZnS

Abstract

The influence of substrate temperature on the condensation and properties of thin films of MgF2 and ZnS was investigated. The properties of films on heated substrates were compared with the properties of films on unheated substrates. In both cases a decrease of film thickness with increasing substrate temperature was observed. In the case of MgF2 the packing density of the films changes from 0.80 to 0.95 with increase of substrate temperature from 40° to 365° C. This change in packing density explains the thickness differences observed. In the case of ZnS, which dissociates during evaporation, the decrease of thickness is due to a decrease of the condensation coefficient of Zn. For the adsorption energy of Zn on ZnS, 4.2 kcal/mol were calculated from the experimental data.