Electronic promotion of silicon nitridation by alkali metals

We report the first observation of a catalytic nitridation of a semiconductor with molecular nitrogen. The Si(100)2×1 surface modified by a sodium monolayer was studied by core-level and valence-band photoemission spectroscopy and work-function measurements using synchrotron radiation. At room temperature, the exposure to molecular nitrogen resulted in Si—N bond formation. The sodium is removed from the surface by thermal desorption at moderate temperature leading to the formation of a clean ${\mathrm{Si}}_3$ ${\mathrm{N}}_4$-Si interface at a much lower temperature than without the alkali metal.