Amorphous and polycrystalline Ge-metal films prepared by physical vapour deposition

Abstract

Amorphous and polycrystalline Ge-metal (aluminium, gallium, silver, gold, copper and iron) films with varying metal concentrations were prepared by codeposition onto glass or rocksalt substrates. Amorphous Ge-metal films were obtained by deposition onto substrates maintained at or below 300 K, whereas polycrystalline films were obtained by deposition onto substrates maintained at elevated temperatures ( > 700 K). The structural order, microstructure and structural stability of these films were established by transmission electron microscopy and electron diffraction. The structural and electrical properties of the amorphous Ge-metal films are consistent with the formation of homogeneous alloys and impurity states introduced on alloying. However, the formation of alloys and/or heterogeneous Ge-segregated metal/compound in crystalline Ge-metal films at high metal concentrations explains the observed behaviour.