Hydrogen adsorption and desorption on SiGe investigated by in situ surfaceinfrared spectroscopy

The hydrogen adsorption and desorption processes in SiGe films epitaxially grown on Si(100), were investigated using in situ infrared absorption spect roscopy (IRAS) in the multiple internal reflection geometry. We have measur ed Si-H and Ge-H stretching vibration spectra to examine how the distributi on of hydride species (SiHx and GeHx) changes while exposed to atomic hydro gen at room temperature, and also to follow chemical changes of the H-expos ed SiGe surface caused by thermal annealing. IRAS data demonstrate that the SiGe surface that is exposed to hydrogen after annealing at approximately 700 degrees, is dominantly covered with Ge hydrides. When the surface is an nealed up to approximately 400 degrees the Ge-H vibration peak vanished com pletely, and instead, the Si-H vibration peak increased its intensity. We s uggest that upon thermal annealing the hydrogen adatoms migrate from Ge sit es to Si sites and the Ge atoms on the outermost layer are replaced with th e inner Si atoms. (C) 1999 Elsevier Science S.A. All rights reserved.