Growth of large-scale GaN nanowires and tubes by direct reaction of Ga with NH3

Large-scale wurtzite GaN nanowires and nanotubes were grown by direct reaction of metal gallium vapor with flowing ammonia in an 850–900 °C horizontal oven. The cylindrical structures were as long as 500 μm with diameters between 26 and ∼100 nm. Transmission electron microscopy, scanning electron microscopy, and x-ray diffraction were used to measure the size and structures of the samples. Preliminary results show that the size of the nanowires depends on the temperature and the NH3 flow rate. The growth mechanism is discussed briefly. The simple method presented here demonstrates that GaN nanowires can be grown without the use of a template or catalyst, as reported elsewhere.