Thermal and photostimulated reactions on Si2H6-adsorbed Si(100)2×1 surfaces: Mechanisms of Si film growth by atomic-layer epitaxy

Abstract

Electron energy-loss spectroscopy (EELS) and reflection high-energy electron diffraction (RHEED) have been used to investigate thermal and photothermal reactions in dihydride (1×1)::2H surfaces obtained by dosing clean Si(100)2×1 surfaces to a saturation exposure (≊2×1017 cm−2) of Si2H6 at 300 K. With 15-s anneals at progressively higher temperatures, the (1×1)::2H was transformed to a (2×1):H monohydride phase at temperatures between 655 and 725 K and most of the remaining H evolved by 765 K. Complete recovery of the initial clean-surface EELS spectrum and 2×1 RHEED pattern, signaling deposition of one layer of epitaxial Si(100)2×1, was obtained between 845 and 955 K. One pulse of 120 mJ cm−2 ArF laser-beam irradiation resulted in significant hydrogen evolution from Si2H6-saturated dihydride surfaces at 300 K and complete hydrogen desorption, with the reestablishment of the initial clean-surface EELS spectrum, at 525 K. The mechanism was found to be photothermal rather than photolytic and the maximum temperature during the ≊20-ns pulse (at 525-K starting temperature) was calculated to be 800 K. RHEED patterns from dihydride surfaces irradiated at 525 K were 2×1, but with slightly weakened half-order diffraction spot intensities. In initial film growth experiments using continuous Si2H6 dosing and pulsed ArF laser irradiation, epitaxial Si was obtained at a steady-state temperature of 525 K.