A Metastable-atom Deexcitation Spectroscopy (MDS) study on the First Atomic Layer of a Polycrystalline Titanium Surface

Abstract

ABSTRACTThe oxygen adsorption on a polycrystalline titanium surface at room temperature has been studied by MDS in conjunction with UPS and AES. MDS and UPS spectra were measured using a pulsed-dischaxge-type metastable helium atom source which we have newly developed. FRom the analysis of the measured spectra, we found the following about the local density of states (LDOS) of the oxygen-adsorbed titanium surface: (1) With increasing oxygen exposure at 0-2 L, the LDOS on the first atomic layer (SDOS) at 0-1 eV below the Fermi level (EF) decreases more steeply than that of deeper layers. (2) The SDOS at 5–8 eV below EF remains small at 0-2 L, and begins to increase at ca. 2 L while the LDOS of subsurface layer increases first. We discuss the positions of adsorbed oxygen atoms based on these results.