✍ Scribed by M. Lindgren; T. Lepistö
No coin nor oath required. For personal study only.
multilayers and single layers of materials indicate that free lattice parameters are different. For Au the differences are smaller than for Ni and this may be caused by differences in the atomic form factor.
For Cu/Ni the simulations of the AXRD profiles were also performed for three period stacks, each period consisting of 15 planes of Ni and 15 planes of Cu. The average width of the grains and vertical mosaicity were as for Au/Ni. The simulated sample consisted of 300 grains and we assumed a (001) fiber texture. In this case we assumed that the in-plane coherency was not completely lost (r coh = 0.8) because in such a case only one broad peak appeared in the reciprocal space map. This is caused by a very small difference in lattice spacing of sublayers and by a small difference in atomic factors.
For the simulation we chose areas around 113, 313, and 402 Cu and Ni planes at W = 25.24, 46.50, 63.44. We simulated maps for 1 and 1.6 % tension strain for Cu in the growth direction that leads to compression deformation of 0.57 and 0.9 % of interplanar distance for Ni in the growth direction. As for Au/Ni we calculate reciprocal space maps for single layers of Cu and Ni, in which the crystalline structure was deformed as in multilayers. Results of both calculations for 1.6 % deformation of Cu are given in Figure , which shows differences in the position of peaks obtained for multilayers and single layers of materials. In this case we can not draw a regression line because the points on the diagram are not in a straight line, suggesting that the dependence of deformation on sin 2 W is not linear.
We can conclude that applying the sin 2 W method to multilayers may give strain (and stress) parameters that are very different from the real ones. We should be very cautious about using this method for multilayered systems and should always use an additional method to determine the strains in such systems. In multilayered systems having satellite peaks in the high-angle AXRD profiles the sin 2 W method cannot be applied.
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