ZnO films grown on Si substrates with au nanocrystallites as nuclei

ZnO films were grown on Si substrates with Au nanocrystallites at different temperatures. The morphologies of Au at different annealing temperatures suggest that Au nanocrystallites can perform in the role of crystal nucleus. Surface morphologies of as-grown ZnO films were characterized as a number of hexagonal heaps in the size range of 3-5 mu m by scanning electron microscopy. X-ray diffraction data support the theory that the ZnO grains are well-aligned in the c-axis. Cathodoluminescence mappings show that the ultraviolet emission at the band edge is suppressed on top of the hexagonal heap in which the green band is intense. The red shift of the E-2 mode demonstrates that the ZnO films in our work are under a weak tensile stress. This should be attributed to the effect of Au nanocrystallites. The convergent beam electron diffraction (CBED) patterns further reveal that the ZnO films grow in Zn-polar. An ab initio simulation agrees well with the results obtained from the CBED images and provides an intrinsic geometry of the growth of ZnO films.