SI(100)2 X-1 - THE CLEAN AND AMMONIA EXPOSED SURFACE STUDIED WITH HIGH-RESOLUTION CORE-LEVEL SPECTROSCOPY

High resolution core-level spectroscopy was utilized to study the clean and NH3 exposed Si(100)2 x 1 surface. The clean surface exhibits two approximately equal intensity surface core-level components at -0.48 and 0.28 eV binding energy referred to the bulk component. NH3 exposure at 300 K induces two surface core-level components at 0.31 and 0.72 eV relative binding energy that can be assigned to surface Si atoms bonded to H and NH2, respectively. Alternative interpretations for the adsorption based on different interpretations of the clean surface core-level spectra are discussed. The steps between adsorption at 300 K and the beginning of subsurface silicon nitride formation by annealing the surface up to 1000 K are investigated.