Synthesis And Luminescence Properties Of Quasi-one-dimensional AIN Nanostructures

The synthesis of quasi-one-dimensional nanomaterials has become investigativefocus and foreland in nanomaterials science. The reason is the synthesis ofquasi-one-dimensional nanostructures are the basis of understanding nanomaterialsphysical characteristics and building a nano-functional devices. It exhibits many uniqueproperties which are different from the bulk materials in optics, electricity andmachinery. The quasi-one-dimensional nanostructure has wide prospect application inthe manufacture of novel nano optoelectronic device. In the recent years, as animportant wide band gap semiconductor materials, the study of synthesis and propertiesof low dimensionality AlN nanostructures has attracted many attention.In this thesis, we synthesized a variety of morphologies of AlN nanostructures, suchas nanocones, nanorods, nanobelts, nanosheets, nanowires were by solid-phase sourcechemical vapor transport method using a self-made vacuum tube furnace depositionsystem. The growth of quasi-one-dimensional AlN nanostructures was controlled bychanging the experimental parameters, mainly include the temperature, flow rate,substrate, and the substrate position. The microstructures and morphology of AlNnanostructures were characterized by X ray diffraction (XRD), scanning electronmicroscopy (SEM) and transmission electron microscopy (TEM). The optical propertiesof quasi-one-dimensional AlN nanostructures were measured by photoluminescence andFourier infrared spectrometer. The results are that as follows: the morphology ofquasi-one-dimensional AlN nanostructures are controlled by adjusting the reactiontemperature, gas flow rate and others parameters. The higher the temperature, thealuminum is more easily diffused on the epitaxial growth surface of the AlN crystal.With the ammonia flow becoming greater, the nitrogen source flows become largerrelatively. In the meantime, it will promote nitriding of Al and suppress the diffusion ofthe aluminum vapor in the epitaxial growth surface of the AlN crystals. The two combined factors affect the morphology of the AlN nanostructures.Quasi-one-dimensional AlN nanostructures grow along c axis direction of wurtzitestructure, the growth mechanism can be explained by the gas-solid growth mechanism.For the quasi-one-dimensional AlN nanostructures, the morphology can affect theluminescence characteristics, and high concentrations of defects lead to the greaterchance of the luminescence and the stronger emission intensity. Blue green range ofluminescence peak in AlN nanostructure mainly are related by defect levels, which arecaused by the Al (or N) vacancy and O impurities. AlN nanostructures show a widerinfrared absorption peak than AlN single crystal.