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

A214 Surface Science 184 (1987) 335-344 North-Holland, A m s t e r d a m ELECTRON EXCITED

ENERGY STATES

H. BEHNER, and

335

LOSS

STUDY

OF THE

ELECTRONICALLY

OF ADSORBED CO2: C A S E

W. SPIESS,

G. WEDLER,

STUDY

CO2/Fe

D. BORGMANN

H.-J. FREUND

lnstitut fiir Physikalische und Theoretische Chemie. Unwersitdt Erlangen Niirnberg, Egerlandstrasse 3, D-8520 Erlangen, Fed. Rep. of Gerrnan.v Received 6 November 1986; accepted for publication 5 January 1987

Electron energy loss (EEL) spectra of CO z adsorbed and condensed on Fe(111 ), Fe(110) and stepped F e ( l l 0 ) are presented. Linear adsorbed or condensed CO 2 shows losses at 6, 8.5. 12, 13.3 and 15.3 eV. These spectra are compared with electronic excitations of gaseous CO 2.

Surface Science 184 (1987) 345-358 North-Holland, Amsterdam OXIDATION ELECTRON

OF lnAs(ll0) ENERGY

PHOTOEMISSION H.-U.

BAIER,

345 SURFACES:

LOSS

AND

AUGER

ELECTRON,

ULTRAVIOLET

SPECTROSCOPY

L. K O E N D E R S

and W. MONCH

Laboratorium fftr FestkOrperphysik, Universitiit Duisburg, D-4100 Duisburgo Fed. Rep. of Germany Received 25 July 1986; accepted for publication 23 January 1987 The interaction of unexcited, molecular oxygen with clean cleaved I n A s ( l l 0 ) surfaces was studied at room temperature. As with the (110) surfaces of other I I I - V compound semiconductors, the oxygen uptake proceeds in three consecutive stages, S, Tj and T2, 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 Evs 3.9 eV and extra features in the emission from the In(4d) core levels. Two new contributions c 1 and c2 to the ln(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 D 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.