Coverage-dependent thermal reactions of digermane on Si(100)-(2×1)

Abstract

In this study, we examine the adsorption and thermal reactions of digermane (${\mathrm{Ge}}_2$ ${\mathrm{H}}_6$) on the Si(100)-(2×1) surface with high-resolution core-level photoemission spectroscopy using synchrotron radiation. At 325 K, the digermane dissociatively chemisorbed to produce ${\mathrm{GeH}}_3$, ${\mathrm{GeH}}_2$, GeH, and SiH species. The sticking coefficient at zero coverage deduced from the photoemission intensity is ∼0.5. Successive annealing of the digermane-saturated surface to higher temperatures causes further decomposition of ${\mathrm{GeH}}_3$ and ${\mathrm{GeH}}_2$ and the desorption H from GeH and SiH, leaving atomic Ge on the surface. In light of the sufficiently large chemical and surface shifts in their core-level binding energies for different surface species, those processes were identified by examining the evolution of Ge 3d and Si 2p line shapes. Experimental results indicate that the reaction for H release from GeH not only occurred in a large temperature range but also depended heavily on the ${\mathrm{Ge}}_2$ ${\mathrm{H}}_6$ adsorption coverages. Two reaction routes for H release from Ge sites were used to describe the large reaction temperature spreads accurately. GeH decomposition by transferring the H atom to a surface Si dangling bond took place for low coverages at ≤590 K, and ${\mathrm{H}}_2$ thermal desorption occurred for higher coverages in the range of 590–770 K. The former process of atom transfer of H from Ge to Si sites was directly observed in the Ge 3d and Si 2p photoemission spectra. © 1996 The American Physical Society.