Elastic strains in epitaxial vacuum-deposited germanium on silicon

Abstract

Abstract The lattice parameters of epitaxial Ge films vacuum-deposited on chemically thinned (111) Si crystals held at 700°–900°C have been determined by selected are electron diffraction. The films were deposited at 12 A/s and their average thicknesses ranged from 25–600 A. In each deposit the Ge parameter was found to be contracted significantly from the bulk value. Contractions ranged from 0.2 to 2% for films prepared at substrate temperatures ranging from 700°–900°C, but were relatively insensitive to the amount of material deposited. In the case of the 25 A deposit prepared at 900°C, the lattice parameters of individual islands in the deposit were found to be contracted from 1.4% for an island on a relatively thick portion of the substrate to 4.2% (complete accommodation of the atomic misfit) for islands near the edge of the polished hole in the substrate. In the latter area, the GeSi bicrystal regions were found to be symmetrically bent, with radii of curvature of about 1 μ. The results are discussed in terms of the theory of crystal interfaces.