Characterisation of anodic oxide films on Sb+Bi alloys in 1 M H3PO4 by photocurrent and capacitance measurements

An attempt is made to determine the basic electrical and electrochemical characteristics of anodic oxide films on Sb and Sb + Bi alloys in molar phosphoric acid: field strength in the film, diffusivity of the main charge carriers, polarizability of the film/solution interface, dielectric constant of the layer, mobility gap and flatband potential. The procedure is based on the assumptions that the anodic film grows via oxygen vacancy transport and can be regarded as a series combination of a semiconductor region adjacent to the metal/film interface and an insulator region extending in the film bulk. The light-induced electronic conductivity of the layer is shown to obey a Poole-Frenkel mechanism of generation of electric carriers. The structure and properties of the layers as depending on the oxidation potential and the Bi content in the alloy are discussed. (C) 1997 Elsevier Science S.A.