Sensitivity of second harmonic generation to space charge effects at Si(111 )/electrolyte and Si(111 )/SiO~electrolyte trolyte interfaces

The potential dependence in the surlace second hannonic response from hydrogen terminated n-Si(111) i(l l and oxidized n-Si(1l1) ll surfaces has been examined in aqueous NH4F and H2S04 4 solutions. The relative phase of the nonlinear response as measured by rotational anisotropy experiments is found to be highly sensitive to the presence of the oxide and the field applied across Si(ll I)/mdde/electrolyte the lll)/oxide/ele t interlace. These observations are attributed to field effects within the space-charge region of the semiconductor which vary with the presence and thickness of the Si(11 1) insulating oxide layer on the i(lll surlace.