Double layer structure and electrode processes on elementary and oxide semiconductors

Abstract The influence of semiconductor properties upon electrochemical and photoelectrochemical behaviour has been studied for germanium, silicon, oxidized silver, titanum and tantalum by means of electrochemical and photoelectrochemical methods. Although the interface structure in each system is very specific, the influence of semiconductor properties upon the potential distribution on the interface and, consequently, upon the kinetics of electrochemical and photoelectrial process, has a common feature-the localization of a considerable part of the overvoltage in a space-charge region and in the adsorbed layer of dipoles and ion-radicals that take part in the process. It is concluded that the barrier layer on oxidized electrodes arises as a result of adsorption and penetration of oxygen into the oxide surface layer at the oxide/solution interface. A mechanism of self-dissolution and passivation of silicon in alkaline solution is proposed. Self-dissolution is mainly chemical and only a small part of the process is electrochemical. New phenomena of the dual effect of light of this system have been discovered-photoactivation and photopassivation of self-dissolution. These phenomena are caused by different bonds of adsorbed oxygen on the silicon surface, which determine the potential distribution at the silicon/solution interface.