Abstract
We have studied the interaction of O with GaAs(110) at 25 K as a function of photon beam exposure, using photoemission to detect and characterize reactions. The results show that x rays (hν=1486 and 1253 eV, photon flux 6.8× and 2.3× photons ) induce O dissociation and surface oxidation while ultraviolet photons do not within our detectability limit (hν=21.2 and 40.8 eV). The primary dissociation process for physisorbed O involves the attachment of low-energy secondary electrons created by photoillumination. Following electron capture, O dissociation produces ions that react with GaAs to yield surface Ga and As oxides. Dissociation also produces molecules that desorb without reacting but can be kinetically trapped at low temperature. The As oxides exhibit -like, -like, and intermediate -like bonding configurations in relative amounts determined by kinetic constraints and oxygen availability. The photon-enhanced formation of a thick oxide at low temperature is limited by diffusion through the oxide layer, and the formation of molecules is observed. Warming to 300 K enhances growth at the expense of As-O configurations.
- Received 9 July 1990
DOI:https://doi.org/10.1103/PhysRevB.42.9080
©1990 American Physical Society