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 Si₃{N}₄$-Si interface at a much lower temperature than without the alkali metal.