Surface Structure Analytical Method by Extended Appearance Potential Fine Structure

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We measured the EAPFS spectra using a measuring system of the Auger electron appearance potential(AEAPS) spectra, since both could be obtained as a function of the primary electron energy. The fine structure was recorded in the second-derivative mode. A personal computer was used for initially setting the accelarating voltage as well as for averaging the addition of data points in order to improve the signal-to-noise ratio. The data were stored on a floppy disk. As the samples, polycrystalline Cr, evaporated Ti thin film and amorphous TiFe alloy film were used. 1. Polycrystalline Cr: we obtained a nearest-neighbour atomic spacing of 2.53A(1=0), 2.54A(1=1) and 2.54A(1=2), respectively. These values are in good agreement with the bulk values(2.50A).2. Evaporated Ti thin film: we obtained a nearest-neighbour atomic spacing of 2.93A (1=0),2.93A(1=1) and 2.58A(1=2) by analyzing the fine structure above the <L_2> threshold. On the other hand, the results of 3.29A(1=0), 3.29A(1=1) and 2.97A(1=2) were obtained from the fine structure above the <L_3> threshold. As a nearest-neighbour atomic spacing of bulk Ti is 2.91A, it is considered that the trantition into 1=0 and 1=1 occure prominantly at the <L_1> excitation. The transition to 1=2 is prominant at the <L_3> excitation.3. Amorphous TiFe alloy film: we obtained a nearest-neighbour atomic spacing of 2.58A (1=0), 2.44A(1=1) and 2.31(1=2), respectively by analyzing the fine structure above the Ti- <L_1> threshold and obtained 2.87A, 2.77A and 2.57A above the Ti- <L_3> threshold. As there are no data about the atomic spacing of amorphous TiFe alloy, we can not decide the prominant level of the final state. But, as the same distribution angular momenta in the final state can be assumed in spite of the differing chemical environment, we can estimate a nearest-neighbour spacing of about 2.5A.