Novel silicon oxide nanojunction structures with various shapes, such as X type, Y type, T type, ringlike and treelike, are fabricated in a self-assembled manner by the hydrothermal method without any metallic catalyst. In the silicon oxide nanojunctions, both the silicon oxide nanowire part and the junction part consist of the same chemical composition, forming homogeneous homojunctions and being made suitable for application in nanoscale optoelectronics devices. The formation of silicon oxide nanojunctions may be influenced by the surrounding environment in the reaction kettle, growth space among the silicon oxide nanowires and the weight of SiO droplets at the growth tip.

GaN thin films were grown on Si(1 1 1) substrates using a pulsed KrF excimer laser-deposition system, and post-annealing was examined to improve the films' quality. In order to investigate the effect of thermal annealing temperature on the crystalline quality, optical properties and surface morphology of the samples, after deposition, the samples were subsequently annealed at different temperatures in ammonia (NH 3 ) ambience for 15 min. The annealed films were characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), Raman spectra and photoluminescence spectra. The measured results show that annealing temperature plays an important role in improving the quality of GaN films, polycrystalline wurtzite structure GaN thin films with c-axis preferred orientation were successfully obtained by annealing, and the optimum annealing temperature is 1100 • C.