Optical second harmonic spectroscopy of boron-reconstructed Si(001)

Optical second harmonic generation (SHG) spectroscopy is used to probe Si(0 01) following thermal decomposition of diborane at the surface. Incorporati on of boron (B) at second layer substitutional sires at H-free Si(001) inte nsifies and redshifts the E-1 SHG spectral peak, while subsequent H termina tion further intensifies and blueshifts E-1, in sharp contrast to the effec t of hulk B doping or nonsubstitutional B. Ab initio pseudopotential and se miempirical tight binding calculations independently reproduce these unique trends, and attribute them to the: surface electric field associated with charge transfer to electrically active B accepters, and rehybridization of atomic bonds.