Single crystal growth of one-dimensional GaN nanostructures by halide vapor-phase epitaxy

High-quality one-dimensional GaN rods and nanowires were grown on Ni-coated c-plan sapphire substrate using halide vapor-phase epitaxy (HVPE). Their structure and optical properties were investigated by X-ray diffractometery, scanning and transmission electron microscopy, and photoluminescence techniques. A high density of straight and aligned one-dimensional GaN nanowires with a diameter of 80 nm was uniformly formed on the entire substrate at 700^∘C. The X-ray diffraction patterns, transmission electron microscopic images, and selective area electron diffraction patterns indicate that the one-dimensional GaN are nanostructure pure single crystals preferentially oriented in the [001] direction. Photoluminescence analysis revealed that the HVPE grown GaN nanowires have high optical quality.     

Dependence of Magnetoresistance on the Thickness of a Dusted Al Spacer Inserted in CoFe／Cu／CoFe Sandwiches

A series of CoFe(4nm)/Cu(X nm)Al(Y nm)/CoFe(6 nm） samples have been prepared at room temperature.An exponential decay of the GMR (Giant Magnetoresistance) with Y was observed for fixed X=2nm.The characteristic decay parameter of Al is obtained to be about 0.26nm,which is rather close to 1 monolayer for Al.A coexistant state of GMR and AMR (anisotropic magnetoresistance) was observed when Y=2nm.As the Cu spacer is replaced by Al layer,only AMR effect dominates.The experimental data further underline the important role played by the nonmagnetic spacers.