Thermoelasticity and interdiffusion in CuNi multilayers

X-ray scattering experiments on coherent CuNi multilayers are performed at various annealing temperatures. First, we show that the classical thermoelasticity theory can be applied in such nanosamples to link composition and strain fields at intermediate temperature. Second, when interdiffusion takes place at higher temperature, the satellite peaks measured at different annealing times indicate the presence of a layer-by-layer interdiffusion mode controlled by the asymmetry of the atomic mobilities in this system.

Figure 1

Experimental (circle) and calculated (thick line) out-of-plane x-ray diffractogram (a) first order 002 and (b) second order 004 from a CuNi 25 [Cu${}_{2.48\text{nm}}$Ni${}_{3.75\text{nm}}$] bilayers at 298 K. In-plane 200 measurement is shown in the inset.

Figure 2

Experimental (symbols) and calculated (lines) out-of-plane x-ray diffractograms obtained at first order 002 for different temperatures ($T=$ 298, 363, and 458 K) from CuNi 25 [Cu${}_{2.48\text{nm}}$Ni${}_{3.75\text{nm}}$] bilayers.

Figure 3

First order 002 out-of-plane x-ray diffractograms measured ex situ at room temperature after different annealing time (in hours) at 670 K for the CuNi sample 1 made of 25 [Cu${}_{2.77\text{nm}}$Ni${}_{2.86\text{nm}}$] bilayers. In-plane 200 measurements are shown in the inset.

Figure 4

Evolution of the experimental intensities (symbols) of the satellite peak from the first order 002 out-of-plane x-ray diffractograms obtained at 670 K: (a) CuNi sample 1 made of 25 [Cu${}_{2.77\text{nm}}$Ni${}_{2.86\text{nm}}$] bilayers and (b) CuNi sample 2 made of 25 [Cu${}_{2.94\text{nm}}$Ni${}_{4.09\text{nm}}$] bilayers. Lines show the results of our kinetic mean-field simulations [see text].

Figure 5

Sequence of instantaneous concentration profiles resulting from our simulations to model the kinetics in Fig. 4 for (a) sample 1 and (b) sample 2.