Simple chemical routes to diamond-cubic germanium-tin alloys

We report the development of a simple chemical route to growing Ge1-xSnx se miconductors using ultrahigh-vacuum chemical vapor deposition and the molec ular precursor (Ph)SnD3 as the source of Sn atoms. Thin films were deposite d on oxidized and oxide-free Si by reactions of (Ph)SnD3 with Ge2H6 at 350 degreesC. The composition, microstructure, and bonding properties of the fi lms were characterized by Rutherford backscattering, high-resolution analyt ical electron microscopy, and Raman spectroscopy. As-deposited Ge1-xSnx on oxidized Si displayed good crystallinity which improved significantly by an nealing at 400 degreesC. High-resolution electron microscopy and diffractio n indicated a diamond-cubic structure with lattice constants intermediate t o those of Ge and alpha -Sn. As-deposited Ge1-xSnx on pure Si was monocryst alline and epitaxial. Nanoprobe analysis in plan view and cross section rev ealed that the as-deposited and annealed materials were homogeneous with go od chemical purity. The Raman spectra showed bands corresponding to Ge-Ge a nd Sn-Ge vibrations with frequencies consistent with a random tetrahedral a lloy. (C) 2001 American Institute of Physics.