Epitaxial growth of very thin films of germanium

Abstract

The preparation of germanium electron microscopy specimens by chemically polishing slices cut from a single crystal is a standard technique (1). Also, epitaxial growth of germanium on crystalline substrates has been achieved by vapour deposition (2,3). However, the selfsupporting very thin films required for high resolution, crystal lattice imaging experiments cannot be easily prepared by either method.A uniform amorphous film of germanium of any desired thickness can be prepared, however, by vacuum evaporation of germanium from a tungsten basket onto a suitable substrate at any temperature below 500 K. This amorphous film will crystallize when heated to 675 K or more (2). By controlling the heating of the substrate during evaporation and subsequent crystallization, it is possible to induce epitaxial film growth on single crystal substrates.The work described here has established the conditions necessary for the growth of germanium single crystal films 140Å thick, with [111] and [100] surface orientations.