The local perfection of massive gradient crystals studied by high-energy x-ray diffraction

Structural parameters of bulk crystalline materials can be accessed in a damage-free manner by high-energy X-ray diffraction. Specific parts of the sample can be characterized if they are distinguished by the lattice spacings. This technique is applied for the first time to massive Si₁-_xGe_xcrystals with locally varying concentrations x. The data reveal e.g. an unusual lattice distortion with an in-plane expansion and an out-of-plane contraction if the samples are deposited at high temperature (1350 K). This is opposite to a distortion inferred from the difference in the lattice constants of Si and Ge.