EXPERIMENTAL INVESTIGATION OF CHARGE-TRANSFER AT THE SEMICONDUCTOR ELECTROLYTE JUNCTION

The behavior of the semiconductor/electrolyte contact is dominated by the exchange of charges at the interface. In this respect, an understa nding of the transfer kinetics is vital in the description of the phen omena and few methods are able to unambiguously characterize it. The p roblems related to this question are surveyed, paying particular atten tion to recently developed Tafel plot measurements. The method, based on the systematic determination of the band edge position as a functio n of the current flow, has been applied to some important aspects of t he semiconductor/liquid junction such as corrosion, stabilization mech anisms and the effect of deposition of dispersed catalysts. Chronologi cally, the latter system is at the origin of this type of measurement, when it was realized that the exchange current deduced from Tafel plo ts was identical to that existing between the solution and the deposit ed catalyst. The generalization of this approach in subsequent studies shows that Tafel plots of semiconductor electrodes constitutes a simp le and quantitative technique which can provide real access to transfe r mechanisms. At the same time, our technique highlights the parallel between the electrochemistry at metal and semiconductor substrates. Fo r the latter it is shown that the effect of the different potential dr ops (in the material, in the double layer) at the interface can be exp erimentally uncoupled.