Hydrogen photoevolution at p-type silicon electrodes coated with discontinuous metal layers

Abstract Hydrogen photoevolution at p-type silicon (p-Si) electrodes coated with platinum or gold layers by various methods has been studied in acid solutions. A p-Si electrode coated uniformly with a Pt layer by vacuum evaporation showed a current-potential curve similar to that for a Pt metal electrode, indicating that the Pt/p-Si contact is nearly ohmic. However, after alkali etching this electrode showed good rectifying character in the dark as well as an efficient photocurrent, indicating that the effective barrier height at the Pt/p-Si contact is much increased. Similar results were obtained for Au-coated p-Si electrodes. When Pt was deposited photoelectrochemically on p-Si, it showed an efficient photocurrent, contrary to the electrodes treated by vacuum deposition. These results are explained well by our recently proposed theory on the mechanism of the generation of photovoltages at semiconductor electrodes coated with discontinuous metal layers.