THE ADSORPTION-KINETICS OF MOLECULAR-OXYGEN AND THE DESORPTION-KINETICS OF GEO ON GE(100)

The reaction kinetics of molecular oxygen with the Ge(100) surface have been investigated by using molecular beam relaxation spectroscopy, thermal desorption spectroscopy and Auger electron spectroscopy. The adsorption kinetics over a range of impingement conditions and surface temperatures are well described by a model involving dissociative Langmuir kinetics, with the initial sticking coefficient and the saturation coverage both increasing with surface temperature. The only species observed in desorption was GeO(g), which desorbed with a cosine spatial distribution. At low coverage, desorption followed first-order kinetics with an activation energy of 60 kcal/mol. At coverages greater than 0.07 ML, zero-order kinetics were observed, with the same activation energy. These results are explained in terms of the instantaneous coverage on active sites for desorption.