Oxygen underlayer formation on titanium by “static mode” laser fluorescence and auger spectroscopy

Abstract

A new method for the determination of adsorbate structures based on detailed considerations of relative sputtering yields of the adsorbate and substrate is presented. The method uses Auger spectroscopy to determine, in the present work, the ion-induced desorption cross section of oxygen adsorbed on polycrystalline titanium as a function of monolayer coverage. Laser fluorescence spectroscopy is employed to measure the sputtering yields of titanium as a function of oxygen coverage. Since the origin of sputtered atoms is largely (> 85%) in the surface layer, the relative sputtering yields allow one to decide that oxygen adsorbs as an underlayer for coverages below two monolayers and that the third layer adsorbs as a weakly bound overlayer on polycrystalline titanium at room temperature. TRIM computer calculations confirm these conclusions in that the underlayer structural model is in much closer accord with the experimental yields than are calculations assuming an overlayer model.