Thermal reactions of disilane on Si(100) studied by synchrotron-radiation photoemission

H-terminated Si(100) surfaces were formed by saturation exposure of Si(100) to disilane at room temperature. Annealing these surfaces to progressively higher temperatures resulted in hydrogen desorption. This process, of basic importance to the growth of Si by atomic layer epitaxy using disilane, was studied by synchrotron-radiation photoemission. The Si 2p core-level line shape, the position of the Fermi level within the band gap, the work function, and the ionization potential were measured as a function of annealing temperature. These results revealed two steps in the thermal reaction preceding the recovery of the clean surface. The dihydride radicals on the surface are converted to monohydride radicals at 500610 K, and the monohydride radicals decompose at 700800 K.