Structure Analysis of Evaporated Films in Scanning Electron Microscopy

Abstract

This paper experimentally evaluates the structure of evaporated films commonly employed by SEM users to prevent charging, to reduce specimen damage, and to enhance secondary electron emission. Films of gold, gold-palladium, gold-platinum, platinum-palladium, and chromium were deposited with and without a coating of carbon. The structure of films was studied by high resolution transmission and scanning electron microscopy.
The size of the islands formed is a function of the amount of metal evaporated and the vacuum conditions. As the vacuum level was changed from 2×10^-5 to 1×10^-3 Torr, the shadowing effect decreased. Thus, for uniform surface coverage, lower vacuum may be preferable; however, this is at the expense of increased amounts of metal for evaporation. By using an air jet pointed at the specimen surface, the same effect of uniform surface coverage is obtained, but without requiring additional metal.