Adsorption of atomic oxygen on the Si(110)5×1 surface via interaction with N2O

Abstract

This paper describes the interaction of a clean Si(110) surface, showing a prominent 5×1 superstructure, with N2O at 300 K in UHV. Differential reflectometry in the photon energy range 1.5–4.5 eV, Auger electron spectroscopy, and low-energy electron diffraction have been used to monitor this solid–gas reaction. Chemisorption of atomic oxygen (as released by decomposition of N2O occurs via an immobile precursor state in the initial adsorption stage in which the N2O molecule is weakly bound at the surface. Every stage of the reaction involves oxygen attachment to the dangling bonds, the initial sticking probability being (6.0±0.1)×10−6. This reaction terminates at 0.42±0.06 ML oxygen coverage, thereby leaving part of the dangling bonds unreacted. This phenomenon can be explained from the nature of the dangling bonds at the Si(110) surface: these hybrids point in off-normal directions thus creating a barrier against effective decomposition of the N2O molecule at higher oxygen coverages. Additional exposure to O2 results in a passivating oxygen adlayer at 0.71±0.11 ML coverage. The optical spectrum indicates that the Si(110)5×1 surface probably has several types of (dangling bond) surface states.