Structure determination of Si(100)(2x1)/NH2 using scanned-energy mode photoelectron diffraction

A scanned-energy mode photoelectron diffraction study of the Si(100)(2 x 1) surface with adsorbed NH2 has provided quantitative determination of key structural parameters previously only predicted from theoretical calculations. The N atoms are found to occupy off-atop sites at a dimerized surface Si atom with an N-S1 bondlength of 1.73 +/- 0.03 Angstrom and bond angle relative to the surface normal of 21+/-4 degrees. The positions of Si atoms in the dimer to which the adsorbates are bonded are found to indicate that the marked asymmetry of this dimer on the clean surface is lost as a result of the adsorption. The conclusions are discussed in relation to published results from less direct experimental probes and the results of theoretical model calculations.