Catalytic oxidation of Si(100) and InP(100) surfaces

Abstract

The catalytic oxidation of clean Si(100) and InP(100) surfaces in the presence of a Cs overlayer has been studied by using high resolution electron energy loss spectroscopy (HREELS), photoelectron. Auger and energy loss spectroscopy (XPS, Auger, ELS), and low energy electron diffraction (LEED). At room temperature we obtain, as a function of Cs exposure, saturation for Si(lOO) with a 2 × 1 LEED pattern whereas this is not the case for InP(100). For InP we first observe a 1× 1 structure, which is followed by an amorphous overlayer growth of Cs. This latter effect is probably related to segregation of metallic In on top of the Cs layers. As the amount of Cs actually determines the thickness of the oxide layer, subsequent oxygen exposure results, therefore, in a higher uptake of oxygen for InP compared to that of Si. Annealing the adsorbate/substrate systems at higher temperatures leads to diffusion of oxygen from adsorption sites related to Cs to the semiconductor interface. Simultaneously, different oxidation states at Si and InP are detected. A comparison to oxidation studies of clean Si and InP wafers clearly indicates a strongly enhanced oxidation when using alkali metals like Cs as a catalytic agent. Possible local bond configurations at the interface will be discussed for Si within the framework of existing models. The InP system is much more complicated, and therefore for that system only preliminary results will be presented.