The Investigation Of The Synthesis Of One Dimension GaN Nanostructure By Ammoniating Ga₂O₃/Ti/Si And Ga₂O₃/TiO₂/Si Films

In this paper, GaN nanostructures have been synthesized on Si(111) substrates by ammoniating Ga₂O₃/Ti and Ga₂O₃/TiO₂ films. The growth mechanism of these GaN nanostructures was proposed and discussed briefly based on the investigation of the influences of different growth conditions.First, Ti films were deposited on Si(111) substrates by magnetron sputtering system, and the structure and composition of Ti/Si samples were determined by X-ray diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR). The results indicated that on one hand Ti could react with Si to form TiSi2 easily. On the other hand, Ti could also react with NH3 at high temperature to form TiN. With the temperature increase, both TiSi2 and TiN had the tendency to transform into TiO₂, which is consistent with thermodynamic analysis.GaN nanostructures were fabricated on Si(111) substrates through ammoniating Ga₂O₃/Ti films deposited by magnetron sputtering system. The structure, elemental composition and morphology of the GaN nanostructures were determined by X-ray diffraction(XRD), Fourier transformed infrared spectroscopy(FTIR), X-ray photoelectron energy spectroscopy (XPS), scanning electronic microscope (SEM) and high-resolution transmission electronic microscope (HRTEM). The results 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 and the thickness of the Ti films. With the increase of temperature, the crystalline quality of GaN nanostructures was improved and the diameter of these nanowires was also increased. But the diameter decreased again when the temperature reached 1000℃. Nanostructures with different morphology were fabricated by this sputtering-post-annealing technique with the help of Ti films with different thickness as middle layers. A VS mechanism was still valid in the growth process of GaN nanostructures in this method. The surface energy distribution of the substrate was greatly changed by the reaction between Ti and Si substrate, which may plays an important role in the formation of GaN nanostructures.GaN nanostructures have also been fabricated on Si(111) substrates through ammoniating Ga₂O₃/TiO₂ films deposited by magnetron sputtering system. The structure, elemental composition and morphology of the GaN nanostructures were determined by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electronic microscope (SEM) and high-resolution transmission electronic microscope (HRTEM). The results indicated that the crystallization of GaN films on TiO₂ middle layers was excellent, which suggest that TiO₂ may be a promising material as middle layer for the fabrication of GaN film in other methods. Besides, we also find that these GaN nanostructures were greatly influnced by the ammoniating temperature, the ammoniating time and the thickness of middle layer. The effects of TiO₂ middle layer on the synthesis of GaN nanostructures are also attributed to the change of the surface energy distribution.