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

The interaction of the nitrous oxide (NO) molecule with the Si(001)2×{}1 surface at 25--1150 ^∘{}C 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 ^∘{}C and is assigned to be in the N≡Si₃ 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 ^∘{}C. The core-level spectra also indicate that a further annealing at {~}950 ^∘{}C converts parts of the incorporated N into the stoichiometric silicon nitride on the surface while the desorption of oxygen starts already at {~}850 ^∘{}C. 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.