Different Morphology Of Beta-ga <sub> 2 </ Sub> O <sub> 3 </ Sub> Situ Growth Of Nanostructures And Their Luminescent Properties

Nanowires, cone-like nanowires, hexagonal nanodisks, nanobelts and nanochains ofβ-Ga₂O₃ have been prepared by an in-situ growth method. The hexagonal nanodisks were synthesized for the first time. The morphologies, crystal structures and photoluminescence properties of theseβ-Ga₂O₃ nanostructures were investigated, and the possible growth mechanisms were also proposed to account for the formation of theseβ-Ga₂O₃ nanostructures with different morphologies. These investigative results would provide a base for research of physical and chemical properties and application of theseβ-Ga₂O₃ nanostructures.(1)β-Ga₂O₃ nanowires have been grown on the surface of gallium grains through heating gallium grains in a N₂ gas atmosphere containing a small quantity of oxygen. Theβ-Ga₂O₄ nanowires are single crystalline with a monoclinic structure, the diameter and length of the as-synthesizedβ-Ga₂O₃ nanowires are 50-100 nm and several tens of micrometers, respectively. We have investigated the growth process of nanowires and a possible mechanism was also proposed to account for the formation ofβ-Ga₂O₃ nanowires. Photoluminescence spectrum of theβ-Ga₂O₃ nanowires was measured at room temperature, and a strong blue photoluminescence with peak at 457 nm originated from the recombination of an electron on an oxygen vacancy and a hole on a gallium-oxygen vacancy pair was observed.(2)β-Ga₂O₃ cone-like nanowires have been in-situ grown on the surface of gallium grains and films by heating gallium substrates in air. The controllable synthesis ofβ-Ga₂O₃ nanowires with different diameters and lengths was achieved by adjusting the heating temperature and time. The as-synthesizedβ-Ga₂O₃ nanowires obtained at different temperature are single crystalline with a monoclinic structure and have a controllable diameter and length in the range of 30-100 nm and 0.5-1.5 urn, respectively. A possible mechanism was also proposed to account for the formation ofβ-Ga₂O₃ conelike nanowires. Photoluminescence spectra of theβ-Ga₂O₃ nanowires obtained at different temperatures were measured at room temperature, and two blue photoluminescence with peaks at 430 and 460 nm and a red photoluminescence with peak at 713 nm were observed. The blue light emission intensity increases with the reaction temperature, however, the red light emission intensity hardly change. The blue and red light emissions originate from the recombination of an electron on an oxygen vacancy and a hole on a gallium-oxygen vacancy pair and the nitrogen etc dopants, respectively. (3)β-Ga₂O₃ hexagonal nanodisks, nanobelts and nanochains were prepared by heating gallium grins under a mixed gas atmosphere of N₂, HCl, NH₃ and H₂O. The control over theβ-Ga₂O₃ nanodisks, nanobelts and nanochains was achieved by adjusting the amount of ammonium chloride and the distance between the gallium and ammonium chloride powders. All of the nanodisks, nanobelts and nanochains are single-crystalline with monoclinic structure.β-Ga₂O₃ nanodisks have a regular hexagonal shape, their edge lengths and thicknesses are in the range of 1.3-2.3μm and 120-200 nm, respectively.The lengths and widths of nanobelts are about 100μm and 400-600 nm, respectively. The length of the nanochains is up to 100μm. The effection of ammonium chloride in the growth of nanodisks was discussed and the possible growth mechanisms for theβ-Ga₂O₃ nanostructures with different morphologies were proposed. Photoluminescence properties of theβ-Ga₂O₃nanodisks, nanobelts and nanochains were measured at room temperature.