Resonance in the optical second harmonic response from the Si(111)-Sb interface

Abstract Optical second harmonic generation (SHG) studies of Sb deposition on clean Si(111) under ultra-high vacuum conditions are reported. Measurements have been made of the SH intensity in the growth region of zero to one monolayer (ML). By using appropriate choices of polarisation, surface azimuth and excitation wavelength, the second order nonlinear susceptibility tensor elements χ xxx and χ zxx are isolated and their magnitude is followed with increasing Sb coverage. By choosing an excitation wavelength which produces a resonantly-enhanced SHG signal from the Si(111)7 × 7 surface, deposition of 0.01 ML of Sb can be detected. The χ xxx and χ zxx components respond differently to Sb coverage, in a way which is consistent with the SHG resonant enhancement being due to electronic states associated with the Si adatoms of the Si(111)7 × 7 surface.