Semiconductive properties of anodic niobium oxides

the semiconductive properties of anodic niobium oxides formed at constant potential and constant current density to different final voltages have been examined by mott-schottky analysis. thin anodic oxides were formed on sputtered niobium specimens at constant potential in the range of 2.5 to 10 vag/agcl in a borate buffer solution. thicker oxides were formed, also on sputtered niobium specimens, at a constant current density of 5 ma cm-2 in 0.1 m ammonium pentaborate solution to final voltages of 10, 50 and 100 v. capacitance measurements were performed in a borate buffer solution of ph 8.8, at a frequency range of 200 to 2000 hz, at a sweep rate of 5 mv s-1 from +2.5 to -1 vag/agcl. the results obtained show n-type semiconductor behaviour with a carrier density in the range of 8 ′ 1018 - 6 ′ 1019 cm-3 on films formed to 10 v. thicker films showed lower carrier densities in the range of 1 ′ 1018 - 2 ′ 1018 cm-3 with a calculated charge depletion layer of 33-36 nm.