Composition of the first two atomic layers in Au0.2 Cu0.8 and Au0.8Cu0.2 alloys
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Ratios of the M2,3VV Auger signal of copper for the alloy Au0.2Cu0.8 to that for Cu standard (hCua/hCus) and such a signal of gold for the alloy Au0.8Cu0.2 to that for Au standard (hAua/hAus), expected for particular compositions of the first and second atomic layers of alloys mentioned above and for two incidence angles (0 and 60°) of the primary electron beam in an RFA spectrometer, were calculated with the use of Monte-Carlo computer simulation of the transport of Auger electrons to the sample surface, including elastic and inelastic scattering of those electrons. These ratios were fitted to the corresponding ratios obtained from measurements, which gave the composition of the first and second atomic layers in both alloys. For the Au0.2Cu0.8 alloy, the relative atomic concentrations of copper atoms in the first and second atomic layer XCu1=0.77±0.1 and XCu2=0.93±0.5, respectively, were found while for the Au0.8Cu0.2 alloy XAu1=0.81±0.1 and XAu2=0.44±0.5 were obtained. These results were found to be almost unchanged when the inelastic mean free path of Auger electrons is varied from 0.3 to 0.5 nm and the acceptance angle of the RFA analyzer is varied from 25 to 35° in calculations mentioned above. On the other hand, the change of the measured ratios hAua/hAus or hCua/hCus by 3% changes the XAu1 or XCu1, respectively, by about 0.1. The results obtained are compared with experimental and theoretical results (concerning the AuxCu1−x polycrystalline and crystalline samples) known from the literature. A good qualitative agreement is found.
|Publication status||Published - Mar 2001|
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