| Gallium nitride (GaN) is an excellent chemical semiconductor material and also is one of the most advanced semiconductors in the world. In fact, GaN has been regarded as one of the most promising materials for the fabrication of opto-electronic devices operating in the blue and near-ultraviolet (UV) regions, for instance light-emitting diodes (LEDs) and laser diodes (LDs), because it has large direct energy band gap of 3.4 eV at room temperature. These light sources have promising applications and potential market demands for the high-density storage of opto-information, high-speed laser print, high-brightness and dynamic display in all colors, solid light sources, signal detectors and communication. In addition, GaN has been attracted much attention as a candidate for fabrication of high temperature, high frequency and high power devices. After 1990, the realization of some pivotally technieal methods and the development of materials growth and devices technics made GaN to be the research focus of the world. MOCVD, MBE and HVPE have become dominating techniques to grow GaN materials. Among these methods, MOCVD is the most important and widely used by researchers. But now large-scale application of GaN devices is confined for the reason of costly equipments and complicated technics. Many research institutes and universities in the world are trying to grow GaN materials with simple and lower cost methods.In this paper, GaN one-dimensional nanostructures were prepared through magnetron sputtering and ammoniating progress on Si (111) substrates. The morphology, microstructure, and components of nanostructures were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR) and X-ray photoelectron spectra (XPS) and so on. We also have a primary discussion about the growth progress of GaN nanostructures.The effects on GaN nanostructures, which stem from various experimental conditions such as the thickness of the middle layer, ammoniating temperature and ammoniating time, were discussed.Firstly, Ga2O3/Ta film is deposited on Si (111) substrates by magnetron sputtering system, and then GaN nanostructures were fabricated through ammoniating. The results of these tests indicated that the as-synthesized GaN nanostructures were hexagonal GaN with wurtzite structure. The crystalline quality and morphology of GaN nanostructures were greatly influnced by the ammoniating temperature, ammoniating time and the thickness of the Ta films. With the increase of temperature, the diameter of GaN nanostructures was decreased and some batt-shaped crystals were formed, and then the diameter of GaN nanostructures was increased and these GaN nanostructures changed to be relative smooth. The crystalline quality of these GaN nanostructures was also improved. The samples annealed at 1000℃for 10min exhibited the best crystal quality and morphology. But the crystalline quality falled and the amount of these GaN nanostructures decreased when the temperature keep on increasing(above 1000℃).We can get the best results when the ammoniating time is 10min. Nanostructures with different morphology were fabricated by this sputtering-post-annealing technique with the help of Ta films with different thickness as middle layers. A VLS mechanism was possible valid in the growth process of GaN nanostructures in this method. The Ta film broke up, and then the liquid Ta nanodroplets which act as energetically favorable sites for absorption of gas-phase reactants are formed on the Si surface at high temperature, which may plays an important role in the formation of GaN nanostructures. |
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