SCANNING TUNNELING MICROSCOPE STUDY ON MID-DESORPTION STAGES OF NATIVE OXIDES ON SI(111)

Scanning tunneling microscope images lead us to the conclusion that the thermal desorption of native oxides on Si(111) does not occur layer by layer but through the formation and lateral growth of voids. This conclusion is consistent with results obtained by reflection high-energy electron diffraction, i.e., that in desorption stages, a (7 x 7) pattern appears with streaky diffraction spots due to small diffraction areas and with a background due to an amorphous oxide film on the surface. It also agrees with Auger electron spectroscopy results, that is, the temperature dependence of the oxide area before and during desorption. Nucleation centers for voids have not been identified.