Nitrogen, oxygen, and carbon monoxide chemisorption on polycrystalline titanium surfaces

Abstract

Changes in the secondary electron yield spectrum of polycrystalline titanium have been studied during exposure to nitrogen, oxygen, and carbon monoxide. The derivative of the yield is measured as a function of the energy of the incident electron beam. Spectral features are interpreted in terms of the work function, diffraction effects and Auger electron appearance potentials. From the titanium 2p 3/2 appearance potential edge, it is evident that the number of unfilled 3d binding state of titanium is decreased by exposures to nitrogen or oxygen of less than one Langmuir. Changes in the diffraction features are less obvious at small exposures, and consist largely of quenching structure at high energies. Exposure of the oxygen covered surface to the electron beam produced a large decrease in the work function, while producing no appreciable change in either the diffraction or appearance potential structure. Spectral changes were followed by gas exposure up to 2000 Langmuirs. In the case of oxygen these large exposures result in the formation of titanium oxides.