Local structure determination of NH2 on Si(111)-(7X7)

N 1s scanned-energy mode photoelectron diffraction has been used to determine the local adsorption geometry of adsorbed NH2 species on Si(111) (7 X 7) resulting from reaction with NH3 at room temperature. The results show that NH2 is adsorbed (almost) exclusively atop Si surface rest atoms with a Si-N bond length of 1.71 +/- 0.02 Angstrom and very little modification of the geometry of the Si atoms in the layer below. Any coadsorbed NH on the surface is either of low relative coverage or is also adsorbed in local atop sites. There is evidence that a small fraction (8 +/- 7 %) of the NHx species may occupy sites atop Si surface adatoms