Electrochemical Impedance Spectroscopy of 6H-SiC in Aqueous Hydrofluoric Acid

Polarization and electrochemical impedance spectroscopy of p-type 6H-SiC electrodes in an aqueous hydrofluoric acid solution is performed during the formation of porous SiC. The polarization of p-type SiC permits the identification of the flatband voltage, a Tafel-like region, and a limiting current which is attributed to the onset of the electropolishing regime. For some of the potential range studied over which porous layers form, the impedance data are characterized by a single high-frequency semicircle and there is a second low-frequency semicircle at intermediate potentials. The dependence of the fitted capacitance and resistance on the applied voltage suggests that the SiC-electrolyte interface is controlled under different regimes of potential by the space-charge layer, the interaction with surface states, and the formation of a passivating film. © 2001 The Electrochemical Society. @DOI: 10.1149/1.1396652# All rights reserved.