CURRENT RESPONSES TO AN IMPULSE LASER-LIGHT ILLUMINATION IN SEMICONDUCTOR ELECTRODES

An impulse current response to a short laser pulse was measured using a current-voltage converter with a zero input resistance, which enable d us to provide any band bending of a semiconductor electrode under a potentiostatic condition. The current transient can monitor a net char ge-transfer process across a semiconductor-electrolyte interface becau se the external resistance is almost zero. The current transient was f ound to be characterized by a relaxation time tau = (R(dl) + R(soi))C- sc where R(dl), R(sol), and C-sc are the diffuse double-layer resistan ce, the solution resistance, and the depletion layer capacitance of th e semiconductor. C-sc obtained from the analysis of the current transi ent gave an ideal Mott-Schottky plot. By intentionally increasing the diffuse layer thickness with which R(dl) and then tau increase, the dy namics of protons generated as an oxidation product of water was confi rmed to be monitored from the current transient.