SHG MEASUREMENTS OF N-SI(111) AQUEOUS-SOLUTION INTERFACES

A study of photoelectrochemical Processes at semiconductor electrodes under short-pulse laser irradiation shows that in-situ second harmonic generation (SHG) is feasible in such complex interfacial systems. A N d:YAG laser (532 nm, 7 ns, 40 mW, soft focus 0.2 cm2) was used for SHG in reflection from n-Si(111) electrodes in a p-p polarization configu ration. We investigated the azimuthal dependence of the SHG at oxide-c overed and bare n-Si(111) electrodes with and without Ni deposits. The relatively strong SH signal from an oxide-covered surface originates at the Si/oxide interface. At the bare electrode, the Si/electrolyte i nterface gives rise to a much weaker signal. Deposition of moderate am ounts of Ni on the oxide reduces the SH signal by shadowing the oxide/ silicon interface without changing the azimuthal anisotropy. Complete Ni coverage of bare Si leads to a different SH anisotropy