Preparation And Properties Of One-dimension GaN Nanostructures And GaN Thin Films

In this paper, one-dimension GaN nanostructures were synthesized on Si substratesby ammoniating Ga2O3/BN films. The growth mechanism of these GaN nanostructureswas proposed and discussed based on the investigation of the influence of theammoniating temperature, ammoniating time and the BN films' thickness on theproperties of GaN nanostructures. GaN films were prepared on GaAs and Si substratesby sol-gel method and electrophoretic deposition technique, and the effects of theannealing temperature on the crystalline quality and morphology properties of the GaNfilms were discussed.One-dimension GaN nanostructures were fabricated on Si(111) substrates throughammoniating Ga2O3/BN films deposited by ratio frequency (RF) magnetron sputteringsystem. The structure, elemental composition, morphology and photoluminescenceproperties of the GaN nanostructures were determined by X-ray diffraction (XRD),Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron energyspectroscopy (XPS), scanning electronic microscope (SEM), high-resolutiontransmission electronic microscope (HRTEM) and photoluminescence spectroscopy(PL). The results showed that the as-synthesized one-dimension nanostructures werehexagonal GaN with wurtzite structure. The ammoniating temperature, ammoniatingtime and the thickness of the BN films greatly affected the crystalline quality,morphology and photoluminescence properties of the GaN nanostructures. A strongemission peak at 373nm (ultraviolet band) and a weak emission peak at 434nm (violetband) were found from the GaN nanostructures, which were excited by 320nm light atroom temperature. It was found that the PL intensity of the two emission peaksenhanced with the increase of the ammoniating temperature and time, and the positionsof them had no change. Because the as-prepared GaN nanostructures is too large forquantum confinement, and in fact the Bohr exciton radius of GaN is 11nm. Theemission peak at 373nm has no blue shift of the band-gap emission compared with thebulk GaN. Another emission peak at 434nm may be attributed to the existence ofdefects or surface states. Further detail work is needed to clarify the underlyingmechanism for the PL spectrum of the one-dimension GaN nanostructures. The growthmechanism of the one-dimension GaN nanostructures can be explained as thevapor-solid growth mechanism, of which the BN films play a very important role in theformation process of the GaN crystal nuclei.GaN films were grown on GaAs and Si substrates by sol-gel method. XRD, XPS,SEM and PL were used to analyze the structure, morphology and photoluminescenceproperties of the GaN films. The results showed that high-temperature annealing madefor the crystallization of the GaN crystals. The diameters of the GaN crystallites becamelarger and the crystal quality of the GaN films was improved with the increase of theannealing temperature. The samples annealed at 950℃ for 10min exhibited the bestcrystal quality and morphology. Under 280nm photo-excitation, a strong emission peakat 385nm, as well as two weak emission peaks at 440nm and 475nm, was observed. ThePL intensity of the emission peaks increased with the increasing of the ammoniatingtemperature. The emission peaks at 440nm and 475nm can be ascribed to the radiantcombination from conduct band to the energy level of acceptor impurity. Further detailwork is needed to clarify the underlying mechanism for the PL spectrum of the GaNfilms grown by sol-gel method. Some clusters of nanowires appear on the surface of thesamples annealed at 1000℃ for 10min on Si substrates. Every cluster of the GaNnanowires was grown along a radiant direction. These nanowires were very straight andsmooth, being identified to be hexagonal wurtzite structure GaN single crystal.GaN films were deposited on Si(111) substrates by electrophoretic depositiontechnique, and the effects of the annealing temperature on the properties of the as-grownGaN films were investigated. The structural, compositional, morphologic andluminescent properties of the GaN films were studied in detail. The results indicatedthat the annealing temperature had a great effect on the crystal quality, morphology andphotoluminescence properties of the GaN films.