We report a naturally grown stripe structure with a nanometer scale wavelength in REBa2Cu3O7-δ (RE = Sm and Eu) superconductors investigated with scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). Such a periodic array was unveiled owning to the 3 dimensionally spatial oscillation of RE and Ba around the stoichiometric ratio. The study displayed that novel nanostripes function as robust pinning sites and effectively enhance the peak effect and the irreversibility line at 77K. This illustrates an approach to fabricate high performance REBa2Cu3O7-δ superconductors for application in liquid nitrogen temperature.
We report the influence of nitrogen implantation and annealing on the microstructures and photocatalytic properties of a nanostructured titania (TiO2) film. Titania samples were implanted at 40 keV and ion dose range of 1016/cm2 to 4×1016/cm2. From X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses it was found that the anatase phase of titania predominated with small amount of brookite, and the structure was stable at annealing temperatures up to 973 K. The samples showed narrower XRD peaks corresponding to larger mean-grain sizes comparing to the un-implanted titania samples. The SIMS (secondary ion mass spectroscopy) nitrogen depth profile showed a maximum nitrogen concentration at about 70 nm beneath the film surface. The absorption edge of the titania samples as measured using spectrophotometer was found to shift toward longer wavelengths with the increase of ion dose. The experiments of photodegradation of phenol were performed under a UV illumination for the N-implanted titania film which exhibited improved photocatalytic properties with the increase of annealing temperature.
Gallium nitride (GaN) thin films were grown by laser induced molecular beam epitaxy (LIMBE). Their microstructures were studied by transmission electron microscopy (TEM). Threading dislocations with Burgers vectors of 1/3<1120>, 1/3<1123> and  were observed as common linear defects with predominantly the first type. Additionally, nano-structured planar defects as called domain boundaries were found. Convergent beam electron diffraction (CBED) technique coupled with chemical and cathodoluminescence measurements was employed to characterize the nano-structured domains, indicating that a domain is of Ga-polarity with respect to the adjacent matrix which is of N-polarity. It was found that experimental parameters such as N/Ga ratio were closely associated with the development of domains as well as the surface morphology. High-resolution transmission electron microscopy (HRTEM) results indicate that IDBs have Ga-N bonds between domains and the adjacent matrix without displacements along the c-axis in the basal planes. Upon the determination of the polar property of a thin GaN film and the optimization of experimental conditions, the nano-structured GaN films can be modified and controlled by changing substrate and pre-growing an AlGaN layer and a GaN buffer layer.