Real-Time X-ray Photoemission Spectroscopy Study of Si(001)-2×1 Exposed to Water Vapor: Adsorption Kinetics, Fermi Level Positioning, and Electron Affinity Variations

Abstract

The great advantage of X-ray photoemission spectroscopy, when performed in real time, e.g., during the reaction of a gas with a surface, is the possibility of monitoring in a single experiment both the chemical aspects (adsorption kinetics, bond formation) and the physical ones (Fermi level positioning, variations in the electron affinity). In the present study we examine the reaction of water with Si(001)-2×1 at room temperature in real time not only because water, ubiquitous in (ultra) high-vacuum systems, is the main source of surface defects controlling the surface Fermi level, but also because water-saturated silicon may become an interesting starting surface in the atomic layer deposition of dielectrics on silicon. The question of water adsorption on silicon Si(001)-2×1 is renewed under the following four perspectives: (1) We propose an original kinetic analysis of the water uptake using an integrated form of the precursor model differential equations, underlying a dependence on pressure. (2) We per...