Several investigators found by using standard AES equipment that the peak-to-peak heights of the Zr signals in the energy range tstween 80 eV and 170 eV vary in an unusual way after exposure of the sample to oxygen.'-' Normally the decrease of the Auger signal intensity is more pronounced for the metal signals of lower energy in comparison to those of higher energy. In contrast, in the case of Zr, an oxygen exposure leads to a strongly weakened 144 eV peak, whereas the signals in the energy range between 80 eV and 125 eV remain relatively unaffected.In order to study this phenomenon, a series of high resolution spectra on Zr and ZrO, specimens was taken. The corresponding data sets were processed by applying algorithms for background correction, smoothing, and deconvolution resulting in AES spectra, which are almost free from experimental broadening and loss process artifacts, As a result of this procedure, it becomes apparent that with increasing oxygen content an additional peak gradually appears 7 eV tslow the 144 eV Zr signal, whereas the signals between 80 eV and 125 eV show minor liw shape effects. This new marked Auger transition can be explained by the formation of an oxygen 2p band which enables cross transitions and interatomic transitions to take place. This is confirmed by the density of state calculation performed for itetragonal ZrO, ,' which reveals a 0 2p band in the energy range from -4 eV to -8 eV below the Fermi level. Differentiated spectra of lower resolution, such as used for routine analysis, do not resolve these two signals and therefore show a broad peak of comparatively low intensity at 144 eV. INTRODUCTIONIn the last few years zirconium has turned out to be a very interesting material for many technical applications. For example, Zr is an alloying component for some hydrogen storilge intermetallic compounds (e.g. ZrMn,) and is believed to catalyse the hydrogen uptake.'*1° The metal itself, its oxide ZrO,, and Zr alloys also serve as constructing materials especially for high temperature applications (e.g. Refs 11 and 12). In order to understand i:he properties of the materials it is of great importance to gain information about their surface compositions, which may differ from the bulk compositions due to segregational effects and/or due to the formation of new near-surface phases after gas exposures. AES has shown to be a versatile tool for attaining such information.Several investigators, using the differentiating LockIn-technique and measuring the peak-to-peak amplitudes for quantitatiori of the AES signals, found that the Zr signal intensities vary in an unusual way after exposing the sample to oxygen.'-' In all of these works an extreme weakening of the M,,N,,V signal is reported, * Present address: Bergbauforschung Essen, D4300 Essen, FRG. whereas the MNN transitions at lower energy behave quite normally (the moderate signal weakening is mainly due to dilution effects by the ZrO, formation). Taking into account the escape depth of the Auger electrons only, one would expect that th...
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