Adsorption and reaction of NO on the Si(001) surface

The interaction of the nitrous oxide (NO) molecule with the Si(001)2x1 surface at 25-1150 degreesC was investigated by high-resolution photoemission using synchrotron radiation. N 1s, O 1s, and Si 2p core-level spectra are systematically analyzed. At room temperature, the dissociative adsorption of NO yields two distinct components for both N 1s and O 1s core levels indicating different adsorption species. The major N species is found to be stable up to 850 degreesC and is assigned to be in the NdropSi(3) configuration. These N adsorbates are thought to incorporate into the surface and subsurface Si layers. The minor adsorbate species both for N and O are unstable for an annealing above 650 degreesC. The core-level spectra also indicate that a further annealing at similar to950 degreesC converts parts of the incorporated N into the stoichiometric silicon nitride on the surface while the desorption of oxygen starts already at similar to850 degreesC. The Si 2p spectra for the NO-dosed surfaces could be decomposed with four oxide- or nitride-related components shifted from the bulk component by 0.8, 1.3, 2.1, and 2.9 eV, respectively. The origin of these components is discussed.