The structure of vacuum-deposited cadmium iodide films

Abstract

The structure of cadmium iodide films evaporated onto amorphous carbon substrates has been studied by electron microscopy and diffraction. Films with average think nesses less than about 200 A are found to give random electron diffraction patterns. Thicker films consist of continuous deposits which give electron diffraction patterns similar to a single crystal oriented with its basal plane parallel to the substrate. The formation of a continuous single crystal film on an amorphous substrate indicates that cadmium iodide crystallites which condense on the substrate in the early stages of deposition undergo considerable coalescence and re-orientation as the deposition proceeds. The final orientation of the deposit is consequently independent of the orientations of the initial nuclei.