Amorphous niobium oxide thin films

Amorphous niobium oxide thin films were deposited by unbalanced reactive magnetron sputtering under different conditions of pressure (2 to 4 Pa) and oxygen percentage (9, 17, and 23%). The films were characterized to obtain the relationships between the deposition parameters and the most relevant physical properties (structural, optical, mechanical, surface morphology and optical). The composition was determined by Rutherford backscattering spectroscopy and energy dispersive X-ray spectroscopy. From the results of X-ray diffraction and the composition, we can conclude that for all of the deposition pressures and flow ratios used, the films were stoichiometric Nb2O5 and amorphous. Similarly, the mechanical and optical properties did not show significant variation between the different deposition conditions; all the films were transparent with a bandgap of about 3.4 eV and a hardness around 5 GPa. Concerning the electrochemical properties, the response of the films to DC polarization in a 0.89% NaCl solution was significantly different. The parameters used to compare the electrochemical response were the polarization resistance and the corrosion resistance obtained from the Tafel analysis.