Observation of higher-order hydrogen-desorption kinetics from gas-source-MBE-grown Si(100) surfaces

The hydrogen-desorption process from Si(100) surfaces quenched from gas-source molecular-beam epitaxy using silane has been investigated by the temperature-programmed-desorption method for the hydrogen coverage 0.06<Θ<0.97. An order-plot analysis indicated a reaction order of 1.59, which is in contrast to the first-order desorption kinetics reported for the monohydride phase of Si(100) surfaces formed by atomic hydrogen adsorption. A model calculation involving both first- and second-order desorption kinetics was performed, which successfully reproduced the intermediate reaction order. The presence of atomic roughness on the grown surface is suggested to inhibit formation of paired monohydride dimers, the precursor state for the desorption, by either limiting the migration of surface hydrogens or reducing the number of surface dimers.