SURFACE 2ND-HARMONIC STUDIES OF SI(111)/ELECTROLYTE AND SI(111)/SIO2/ELECTROLYTE INTERFACES

The optical second harmonic (SH) response from Sit (111) electrode surfaces has been studied and has been found to be highly potential dependent. For both H-terminated Si(lll) surfaces in NH4F,,F, and oxide-covered surfaces biased in H2SO4, the phase and the amplitude display a potential dependence which are attributed to field effects within the semiconductor space-charge region and at the surface of the Sit (1 1 1) electrode. These studies are the first to demonstrate that for Sit (111) /oxide samples, the potential dependence in the SH phase can be correlated with oxide thickness, as demonstrated by examining samples of 0-40 Angstrom A thickness.