Optical band gap dependence on the oxalic acid concentration of antimony anodic oxide films

A decrease of the optical band gap of thin films of anodized antimony was observed when the concentration of the oxalic acid used as an electrolyte was increased. The thin films of antimony were obtained using vacuum-thermal evaporation on glass substrates. Electrodes were attached to them and the samples were galvanostaticaly anodized at a constant temperature in a standard two-electrode cell in an aqueous solution of oxalic acid at various concentrations. The normal-incident transmittance and reflectance spectra of the samples were measured and used to calculate by different numerical methods the absorption coefficients and the optical band gaps.