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The sputtering time corresponding to a decrease of the oxygen peak amplitude to 50% of its maximum value in the film was measured and apparent film thickness was calculated from these values assuming a constant sputter rate of 0.6 nm/min. A maximum in the nitrogen peak amplitude is reached at the oxide-metal interface. The nitrogen peak amplitude monitored with a magnification of five, remains close to zero for the film formed at a current density of 0.01 А/cm 2 but it exhibits a finite value which increases with increasing sputter time for the film formed at 0.33 А/cm 2. Carbon present as an impurity on the surface disappears rapidly with sputtering. The amplitude of the oxygen peak decreases whereas that of the nickel peak increases as the oxide film is removed by sputtering. Figure 3.6 shows typical Auger depth profiles of anodic films formed at two different current densities, 0.01 and 0.33 А/cm 2, in 6 M NaNO, + 0.1 M NaOH. AES depth profile analysis provided information about the film thickness and incorporation of electrolyte anions in the film. They were then introduced into the AES vacuum chamber. For AES analysis, the samples after anodic polarization were removed from the ceil, washed with distilled water, and dried. Alkaline solutions were employed to avoid self-activation of the anode after interruption of the polarizing current. Single-crystal nickel (99.95%, orientation ) anodes were used in a flow channel cell through which the electrolyte was pumped at a flow velocity of 1,000 cm/s.