AES study of the adsorption of O2, CO, CO2, and H2O on indium

The adsorption of various oxygen-containing gases on clean polycrystalline In has been studied. For the In–O2 system, the relationship between N (E) areas and dN (E)/dE peak heights for In MNN Auger transition was found to be linear. At saturation, an oxygen/indium ratio of 3/2 was measured, consistent with the formation of the stable oxide In2O3. Low-coverage sticking coefficients were found to be ∠0.014 for O2, ∠0.004 for H2O, ∠2×10−5 for CO, and ∠5×10−5 for CO2. In each case, chemical shifts and peaks distortions in the N (E) and dN (E)/dE spectra have been measured for the gas-saturated In, the largest being ∠3 eV for the MNN transition of O2-saturated surface.