Coherent X-ray diffraction for mapping strains in ZnO nanocrystals

In condensed matter physics, we consider nanometre-sized crystals to be a new frontier of opportunity to tailor physical properties using ''size'' as a control variable. However, when we think about nanostructures, we must reconsider the standard bulk concepts of lattices and crystal defects. Changes here provide nanomaterials with new and exciting properties. This talk will illustrate how coherent X-ray diffraction at a 3rd generation synchrotron source can be used to obtain quantitative three-dimensional maps of the deformation of a crystal from its equilibrium lattice spacing. To invert the diffraction, we have solved the crystallographic ''phase problem'' by oversampling using a support-constrained HIO algorithm. The ZnO crystals we have been investigating were attached by bonding to a SiO2 substrate and show internal strain arising from accidental damage during manipulation. Use of more than one Bragg peak from the same crystal has allowed components of the full strain tensor to be mapped inside the crystal.