Investigation of the void structure in amorphous germanium thin films as a function of low-energy ion bombardment

Abstract

Amorphous germanium thin films were prepared by electron-beam evaporation with low-energy Ar ion assist. The ion energy and ion/atom arrival rate ratio were varied from 15 to 110 eV and between 0% and 25%, respectively. The low-density ‘‘void’’ network structure was observed by transmission electron microscopy and characterized by spectroscopic ellipsometry. The void content of the films was shown to depend strongly on the ion/atom arrival rate ratio and to a lesser extent on the incident ion energy. A more quantitative description of thin-film evolution and important factors which affect it are discussed.