Oxidation of InAs(110) surfaces: Auger electron, electron energy loss and ultraviolet photoemission spectroscopy

Abstract

The interaction of unexcited, molecular oxygen with clean cleaved InAs(110) surfaces was studied at room temperature. As with the (110) surfaces of other III–V compound semiconductors, the oxygen uptake proceeds in three consecutive stages, S, T 1 and T 2 , where in the first stage cleavage-induced defects are saturated while the other two stages comprise the main oxygen uptake. At the initially clean surface, a surface component is observed in the photoemission line from the In(4d) core levels which is shifted by 0.28 eV to larger binding energies with respect to the bulk contribution. In a simple electrostatic model, this surface core-level shift is explained by the difference in Madelung energy in the bulk and at the surface. With the onset of the main oxygen uptake, the photoemission spectra show an O(2p)-related peak at E vs -3.9 eV and extra features in the emission from the In(4d) core levels. Two new contributions c 1 and c 2 to the In(4d) emission-line are obtained which are chemically shifted by 0.07 and 0.49 eV, respectively, to larger binding energies: with the onset of T 1 , component c 1 is found to grow at the expense of the surface component of the clean surface while component c 2 is detected in T 2 only and its increase in intensity is correlated with a decrease of the signal from the bulk. The electron energy loss and the photoemission data agree quite well but in EELS an As(3d) related energy loss shifted by 3 eV to larger loss energies is additionally observed.