Photoelectrochemical characterization of amorphous hydrogenated carbon films

Abstract

Amorphous carbon (a-C:H) films of different thicknesses were grown on tungsten substrates by ion-plasma decomposition or magnetron sputtering. The behaviour of different specimens, corresponding to distinct growth conditions, was investigated in 0.5 M H 2SO 4 solution by photoelectrochemical techniques. Depending on the electrode potential, both anodic and cathodic photocurrents were detected owing to an intrinsic semiconductor-like or insulating behaviour of the samples. Different optical gap values were measured for samples grown in different conditions. The influence of the amorphous nature of the films on their behaviour is also briefly discussed. Evidence was also obtained for the growth, under anodic polarization, of an anodic tungsten oxide underlying the a-C:H film which results in the detachment of the amorphous carbon film from the metallic substrate at high potentials.