Ab initio calculations were carried out to investigate the pathways of H-atom migration and H2 desorption on a mixed SiGe(100)-2x1 surface using the cluster model. The H2 recombinative desorption was the rate-determining step in H migration and desorption on SiGe(100) surfaces, since the energy barrier to H-atom migration was generally lower than that of H2 desorption. The energy barriers for H2 desorption from the interdimer, the Si–Ge pair, (52.8kcal/mol), and the Ge–Ge pair, (45.1kcal/mol), were lower than that for the Si–Si pair by 7.5 and 15.2kcal/mol, respectively. Thus, the SiGe(100)-2x1 surface in chemical vapour deposition provided more dangling bonds than the Si(100)-2x1 surface because of Ge inclusion. In contrast, the chemisorbed H tends to stay on the Si-site, since the barrier for H-migration from the Ge-site to the Si-site was lower that in the opposite direction by 5.6kcal/mol. Hence, a considerably higher percentage of Ge sites were dangling bonds, compared with Si sites on the SiGe(100) surface. Related transition state structures in the migration and desorption steps were also considered.

Study of Pathway of Hydrogen Migration and Desorption on SiGe(100) Surface Using ab initio Calculations. C.L.Cheng, D.S.Tsai, J.C.Jiang: Japanese Journal of Applied Physics, 2005, 44[10], 7625-33