INSITU 2ND-HARMONIC GENERATION MEASUREMENTS DURING THE ELECTRODEPOSITION OF NI ON N-SI(111)

Reflection measurements of optical in situ second harmonic generation (SHG) from n-Si(111) electrodes in contact with various aqueous electr olytes under potentiostatic control in an electrochemical cell are pre sented. Special attention was payd to both oxide-free and oxide-covere d surfaces, and, particularly, to the electroplating of Ni on Si/SiO2. A SiO2-covered surface yields a SH signal by an order of magnitude hi gher than the bare Si surface. The SH azimuthal anisotropy reflects th e C3v Symmetry of the (111) silicon plane superimposed by an additiona l mirror plane which may be explained by surface step arrays due to sl ight misorientation of the (111) surface. With electrodeposited Ni cov erage on the oxidized surface, the SH signal decreases, probably due t o shadowing without substantially changing the symmetry. These facts p oint to the SHG originating from the Si/SiO2 interface.