Photoelectrochemical Study of Anodically Formed Oxide Films on Niobium Surfaces

The semi-conducting properties of electrochemically formed oxide films onto Nb surface in 1 M H2SO4 have been studied by photo-electrochemical measurements. By cyclic voltammetry the I vs. E profile of active/passive transition of Nb electrode has been recorded in the potential region from –0.5 to 8 V (SCE). The photocurrent maximums, band gap energies and flat potentials of anodic oxide films formed by stepwise rising of anodic voltage from 10 to 100 V on Nb electrode have been determined. Using Raman spectroscopy the development of crystalline structure in the films with different resultant thickness has been analysed. The semi-conducting properties of niobium oxides with development of crystalline structure have been discussed in term of breakdown processes in the films. The thresholds of transition from amorphous to crystalline form of anodic oxide films depending of applied voltages and time of polarization have been determined