B. Makarenko

Kinetics of H atom adsorption on Si(100) at 500–650 K

The kinetics of isothermal adsorption and migration of atomic hydrogen on a Si(100) surface has been investigated by the time-of-flight scattering and recoiling spectrometry technique. A continuous decrease in saturation coverage with temperature under constant atomic hydrogen exposure has been observed for temperatures in the range 325–750 K. This observation is in contrast with a widely accepted view of the Si(100)/H surface as having three fixed coverage states within certain temperature windows. For TS=500–650 K, the decrease is described by a kinetic model in which the surface concentration of physisorbed hydrogen atoms is depleted due to the increased rate of migration from precursor sites to primary monohydride sites. The model suggests a mechanism to explain the dependence of the saturation value on temperature in this range. The migration constant obeys an Arrhenius expression with an activation energy of 0.71 eV. A significant concentration of hydrogen atoms occupying precursor states acts as a ...