The effects of chloride ions and benzotriazole on photoresponses of copper electrodes

The effects of chloride ions (Cl-) and benzotriazole (BTA) on a Cu electrode in weakly acidic solution (pH 5.6) and borax buffer solution (pH 8.5) were investigated by measuring the photopotentials, the photocurrent as a function of electrode potential and the intensity modulated photocurrent spectra (IMPS) of the Cu electrode. The photoresponse transition from p-type to n-type was observed in both chloride-containing media and borax buffer containing 0.1 mg/l BTA or above. The photoresponse originated from Cu2O film on the surface of the Cu electrode. The doping of Cl- in the Cu2O film was responsible for the photoresponse transition of the Cu electrode in chloride-containing media. When BTA was added to the solutions, the compact Cu-BTA film was formed and blocked the intrusive ions into the underlying Cu2O film. However, a photoresponse transition was observed with the increase in BTA concentration in borax buffer solutions, It was concluded that the co-existence of heterogeneous p-type region and n-type region in Cu2O film underlayer resulted in the photoresponse transition. (C) 1999 Elsevier Science S.A. All rights reserved.