Abstract
In situ scanning tunneling microscopy and density functional theory (DFT) calculations are employed to investigate single N H3 -molecule-reacted Si (111) -7×7 half cells at room temperature. An N H3 molecule is dissociatively adsorbed on the surface, and each of its fragments, H or N H2, may be adsorbed at an adatom or at a rest atom site. Intermediated by a metastable species, the N H2 adsorbed atop the adatom is transformed into a stable species when negative sample bias voltages are applied for scanning. By using this property, we determine that 12.1% of the reacted adatom sites are capped by N H2 and, in turn, 87.9% of N H2 are bonded with the rest atoms. According to the DFT calculation results, the metastable species and stable species are considered to be the N H2 - and NH-inserted adatom backbond structures, respectively. © 2007 The American Physical Society.