Coherent X-Ray Diffraction of Zinc Oxide Nanocrystals

This report outlines the techniques required to obtain and interpret Coherent X-ray Diffraction (CXD) imaging measurements for crystalline materials. ZnO will be introduced as the principle material under investigation with a brief overview of research to date. Chemical Vapour Transport Deposition (CVTD) was used to synthesise ZnO nanorods, initially Scanning Electron Microscopy (SEM) determined the morphology of the ZnO and CXD was used to probe the internal structure. Applications and limitations of the CXD method are discussed. An overview of the iterative algorithm approach to overcoming the phase problem encountered in CXD and the implications for the structural reconstruction are provided. The interpretation of the resulting reconstruction of a single ZnO nanorod identified strains present. We predicted strain due to the presence of oxygen vacancies in n-type ZnO, confirmation was sought in the form of annealing, plasma treatment and metal deposition experiments designed to vary the oxygen vacancy distribution in a controlled manner. Preliminary results for both annealing and plasma treatment showed no variation in strain, deposition of Iron and subsequent annealing significantly altered the internal structure of the material (CXD) but not the morphology of the crystal (SEM).