Point Defect Model Description of the Formation of Anodic Gold Oxide in H₂SO₄ Solution

An impedance-based Point Defect Model (PDM) was developed for the potentiostatic, anodic formation of gold oxide at potentials of 1.40–1.70 V vs SHE in H 2 SO 4 (0.1 M and 0.5 M). Film thickness and refractive indices were determined at each oxide formation potential using spectroscopic ellipsometry. The thickness of the oxide increases linearly with increasing potential. Mott-Schottky analysis shows that the oxide exhibits both n-type and p-type character and the dominant defect density is calculated to be in the order of 10 21 −10 22 (1 cm −3 ). The PDM was optimized upon experimental EIS data to extract values for model parameters and accounts well for the experimental observations in both the steady-state time and frequency domains.