Depth-resolved strain measurements in polycrystalline multilayers by energy-variable X-ray diffraction

Energy-variable X-ray diffraction technique is further established as a novel method for depth-resolved measurements of residual strains in polycrystalline multilayers. Depth sensitivity is achieved by the controlled varying of the X-ray energy and, hence, X-ray penetration into the sample. In this paper, we develop analytical expression for the energy-dependent shape of the diffraction profile taken from a polycrystalline multilayer. We show that the maximum diffraction intensity recorded in the detector originates at a characteristic depth, Zc, which strongly depends on the X-ray penetration length, as in the case of homogeneous material considered in detail in our earlier publications [E. Zolotoyabko et al. J. Synchrotron Radiation 11 (2004) 309; Nucl. Instr. & Meth. Phys. Res. B 246, (2006) 244]. The multilayer periodicity only weakly influences the previously derived expressions for Zc. The accomplished analysis provides theoretical basis of using the energy-variable diffraction in polycrystalline multilayers. We apply this technique for characterizing the alumina/Ni samples produced by high-temperature diffusion bonding.