In situ optical second harmonic generation studies of electrochemical deposition of tellurium on polycrystalline gold electrodes

Abstract

The electrodeposition of tellurium (Te) on polycrystalline gold electrodes was studied using in situ optical second harmonic generation (SHG) at two different excitation wavelengths. On excitation at 1064 nm, the SH signal decreased dramatically with the first Te underpotential deposition (upd) and increased slightly with the second upd and the bulk deposition of Te. There was a linear correlation between the square root of the SH intensity from the surface and the surface coverage of Te, although the proportionality constant of this correlation for the first Te upd was different from those for the second upd and bulk deposition. This is possibly because of the stronger interaction of the first upd layer of Te than the second and bulk layer of Te with the substrate surface. However, on excitation at 585 nm, the behavior of the SH signal was more complicated, especially during the desorption process of the first Te monolayer. An increase in the SH intensity was observed with the first Te upd, but this increase in SHG still continued in the potential region in which no deposition of Te occurred. These results are interpreted by considering the existence of an optical resonance at the Au surface covered with a Te monolayer.