ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Ion-beam mixing of Fe-Al and Mo-Cr multilayers was studied by alternately sputtering with 5 keV Ar+ and then analyzing with Auger electron spectroscopy. The target temperature was variously room temperature, 450, 525, or 600 K. The two systems were chosen on the basis of having heats of mixing (ΔHm) which were opposite in sign, namely H1:1m=−0.25 eV for solid Fe-Al and ΔH1:1m=+0.075 eV for solid Mo-Cr. (ΔH1:1m applies to a 1:1 composition.) With Fe-Al a well-defined peak broadening was observed as the profiling temperature increased, while with Mo-Cr there was a slight narrowing of the peaks with increasing temperature. The results were analyzed in terms of numerical solutions of a diffusion equation which contained terms appropriate not only to ballistic motion but also to the motion of bombardment-induced residual defects. The latter were assumed to be in part "chemically guided,'' as quantified with the parameter "qp'' (qp∼∝ΔHm). A major difference between Fe-Al and Mo-Cr was found. The peak changes with Fe-Al scaled with what we have termed the effective diffusion coefficient Deff=Dt(1−qp/4). Here Dt is the total diffusion coefficient, i.e., it describes the total diffusivity for all mixing processes. With Mo-Cr, on the other hand, the peak changes scaled approximately with 1/qp. The mixing behavior of Fe-Al, with negative ΔHm, could thus be said to be mainly kinetic (with Deff playing a major role), while that of Mo-Cr, with positive ΔHm, is more nearly thermodynamic (with qp playing a major role). © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.363187
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