COVERAGE-DEPENDENT THERMAL-REACTIONS OF DIGERMANE ON SI(100)-(2X1)

In this study, we examine the adsorption and thermal reactions of dige rmane (Ge6H6) on the Si(100)-(2X1) surface with high-resolution core-l evel photoemission spectroscopy using synchrotron radiation. At 325 K, the digermane dissociatively chemisorbed to produce GeH3, GeH2, GeH, and SiH species. The sticking coefficient at zero coverage deduced fro m the photoemission intensity is similar to 0.5. Successive annealing of rhc digermane-saturated surface tc, higher temperatures causes furt her decomposition of GeH3 and GeH2 and the desorption H from GeH and S iH, leaving atomic Ge on the surface. In light of the sufficiently lar ge chemical and surface shifts in their core-level binding energies fu r different surface species, those processes were identified by examin ing the evolution of Ge 3d and Si 2p line shapes. Experimental results indicate that tile reaction for H release from GeH not only occurred in a large temperature range but also depended heavily on the Ge2H6 ad sorption coverages. To reaction routes for H release from Ge sites wer e 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 less than or equal to 590K, and H -2 thermal desorption occurred for higher coverages ill the range of 5 90-770 K. The former process of atom transfer of H from Ge to Si sites was directiy observed in the Ge 3d and Si 2p photoemission spectra.