Conduction through a SiO2 layer studied by electrochemical impedance analysis

Abstract This study addresses the effect of protons migrating from an aqueous solution on conduction through a dielectric SiO 2 layer thermally synthesized on a highly n-doped silicon electrode (n + -Si). We investigate the conduction process, which involves an electrogenerated radical (hydrogen atom) in an n + -Si/SiO 2 /aqueous system, using electrochemical impedance analysis. With a sufficiently negative potential such as − 2 V (vs. Ag/AgCl), the charge transfer resistance decreases as a function of time and no SiO 2 layer breakdown is observed. A much thicker SiO 2 layer exhibits similar behavior, which ensures negligible tunneling or leakage. Based on a Randles equivalent circuit involving a variable resistance, the impedance responses enable us to see what occurs in the SiO 2 layer in this system. The results strongly imply that the faradaic reduction of protons occurs at the interface between n + -Si and SiO 2 .