Adsorption and Desorption of O2 on GaAs {111} Surfaces

Abstract

A quadrupole mass spectrometer was used to measure the desorption rate of oxides produced by adsorption of oxygen on GaAs polar {111} crystal planes. The results suggest that oxygen is adsorbed dissociatively at Ga surface atoms and is desorbed as Ga2O in a first-order process with an activation energy of 54±4 kcal/mole from the (111) face and 42±4 kcal/mole from the (1̄1̄1̄) face. In agreement with previous work, O2 sticking probability was∼10−4 at low coverage; however, no activation energy for adsorption was detected for the (111) face. Desorption of Ga2O from the (1̄1̄1̄) surface showed evidence of an additional, weaker binding state not present on the (111) surface.