Photoelectrochemical characterization of amorphous anodic films on Ti-6at.%Si

Abstract

The solid state properties of anodic films grown galvanostatically on sputtering-deposited Ti-6at.%Si alloys were studied as a function of the formation voltage (5-40 V). From the photocurrent spectra a band gap of ∼3.4 eV was estimated for all the investigated thicknesses, which is almost coincident with the value measured for amorphous TiO2. The photocharacteristics allowed to estimate the flat band potential of the films, which resulted to be more anodic for thicker layers and allowed to evidence a change from n-type semiconducting material to insulator by increasing the formation voltage. A dielectric constant of ∼31 was estimated by differential capacitance measurements. The dependence of photocurrent on electrode potential was studied in the frame of Onsager-Braun theory, which allows to evidence the influence of the initial recombination on the photocurrent yield for amorphous material.