Sodium-assisted nitrogen adsorption on Si(0 0 1) surfaces at room temperature studied by metastable de-excitation spectroscopy

We have investigated the electronic structure of nitrogen–sodium co-adsorbed layers on the Si(0 0 1) surface by metastable de-excitation spectroscopy (MDS). MDS spectra showed that nitrogen was adsorbed in both atomic and molecular states on Na/Si(0 0 1) surfaces at room temperature. The emission intensity related to the Na 3s-induced states near EF did not decrease but slightly increase upon nitrogen adsorption. With oxygen dosing into the Na/Si(0 0 1) surface, the intensity of the Na 3s-induced peak is markedly reduced. Nevertheless the dissociative adsorption of nitrogen was promoted more efficiently. These results demonstrate a promotional function of Na pre-adsorbates on nitrogen adsorption, but suggest rather unimportance of charge transfer from the Na 3s-induced states to nitrogen molecule.