Structure of Magnesium Fluoride Films on Amorphous Substrates

Abstract

Structure of magnesium fluoride films of thickness from 40 Å to 8000 Å evaporated on optical glass and on fused quartz was studied by means of electron microscope and diffraction and its correlation with optical properties and tenacity of the films was examined. Films deposited at room temperature are amorphous, and the grains remain considerably small and tend to grow in height. Effects of residual gas, contamination of substrate surface and rate of deposition were examined. Films deposited in poor vacuum are shown to be porous in structure. Films deposited on substrate kept above 220°C have [301] preferred orientation, and the grains remain thin and grow along the substrate surface. The causes of tenacity of the films deposited at high substrate temperatures are discussed.