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.