Fabrication of GaN Nanorods in a Large Scale on Si（111）Substrate by Ammoniating Technique

GaN nanorods in a large scale have been synthesized on Si （111） substrates by ammoniating Ga2O3/Mg films under flowing ammonia atmosphere at the temperature of 1000℃ for 15 min. The as-synthesized GaN nanorods are characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and highresolution transmission electron microscopy. The results demonstrate that these straight nanorods are hexagonal wurtzite GaN single crystals in diameters ranging from 200 nm to 600 nm.     

Synthesis and Growth Mechanism： A Novel Fishing Rod-Shaped GaN Nanorods

A novel fishing rod-shaped GaN nanorod is successfully fabricated through a new method by using the two-step growth technology. This growth method is applicable to continuous synthesis and is able to produce a large number of single-crystalline GaN nanorods with a relatively high purity and at a low cost. X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy are used to characterize the as- synthesized nanorods. The results show that most of the nanorods consist of a main rod and a top curved thread. It is single-crystal GaN with hexagonal wurtzite structure. The representative photoluminescence spectrum at room temperature exhibits a strong UV light emission band centered at 370.8nm. Furthermore, a possible two-stage growth mechanism of the fishing rod-shaped GaN nanorod is also briefly discussed.     

Selective Area Growth and Characterization of GaN Nanorods Fabricated by Adjusting the Hydrogen Flow Rate and Growth Temperature with Metal Organic Chemical Vapor Deposition

GaN nanorods are successfully fabricated by adjusting the how rate ratio of hydrogen(H_2)/nitrogen(N_2) and growth temperature of the selective area growth(SAG) method with metal organic chemical vapor deposition(MOCVD).The SAG template is obtained by nanospherical-lens photolithography.It is found that increasing the flow rate of H_2 will change the GaN crystal shape from pyramid to vertical rod,while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale.Finally the GaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H_2:N_2 ratio is 1:1 and the growth temperature is 1030℃.The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy.The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.     

Synthesis of GaN Nanorods by Ammoniating Ga2O3/ZnO Films

Large quantities of CaN nanorods are successfully synthesized on Si（111） substrates by ammoniating the films of Ga2O3/ZnO at 950℃ in a quartz tube. The structure, morphology and optical properties of the as-prepared CaN nanorods are studied by x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence. The results show that the CaN nanorods have a hexagonal wurtzite structure with lengths of several micrometres and diameters from 80 nm to 300hm, which could supply an attractive potential to harmonically incorporate future GaN optoelectronic devices into Si-based large-scale integrated circuits. The growth mechanism is also briefly discussed.     

Growth of β-Ga2O3 nanorods by ammoniating Ga2O3/V thin films on Si substrate

This paper reports that/3-Ga2O3 nanorods have been synthesized by ammoniating Ga2O3 films on a V middle layer deposited on Si（111） substrates. The synthesized nanorods were confirmed as monoclinic Ga2O3 by x-ray diffraction,Fourier transform infrared spectra. Scanning electron microscopy and transmission electron microscopy reveal that the grown β-Ga2O3 nanorods have a smooth and clean surface with diameters ranging from 100 nm to 200 nm and lengths typically up to 2μm. High resolution TEM and selected-area electron diffraction shows that the nanorods are pure monoclinic Ga2O3 single crystal. The photoluminescence spectrum indicates that the Ga2O3 nanorods have a good emission property. The growth mechanism is discussed briefly.     

A study of transition from n-to p-type based on hexagonal WO3 nanorods sensor

Hexagonal WO3 nanorods are fabricated by a facile hydrothermal process at 180 ℃ using sodium tungstate and sodium chloride as starting materials. The morphology, structure, and composition of the prepared nanorods are studied by scanning electron microscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. It is found that the agglomeration of the nanorods is strongly dependent on the PH value of the reaction solution. Uniform and isolated WO3 nanorods with diameters ranging from 100 nm-150 nm and lengths up to several micrometers are obtained at PH = 2.5 and the nanorods are identified as being hexagonal in phase structure. The sensing characteristics of the WO3 nanorod sensor are obtained by measuring the dynamic response to NO2 with concentrations in the range 0.5 ppm-5 ppm and at working temperatures in the range 25 ℃-250 ℃. The obtained WO3 nanorods sensors are found to exhibit opposite sensing behaviors, depending on the working temperature. When being exposed to oxidizing NO2 gas, the WO3 nanorod sensor behaves as an n-type semiconductor as expected when the working temperature is higher than 50 ℃, whereas, it behaves as a p-type semiconductor below 50 ℃. The origin of the n- to p-type transition is correlated with the formation of an inversion layer at the surface of the WO3 nanorod at room temperature. This finding is useful for making new room temperature NO2 sensors based on hexagonal WO3 nanorods.     

Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films

The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si （100） substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700℃. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite （OZn）, interstitial oxygen （Oi）, interstitial zinc （Zni） and zinc vacancy （VZn^-）, which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.     

Synthesis of flower-shape clustering GaN nanorods by ammoniating Ga2O3 films

Flower-shape clustering GaN nanorods are successfully synthesized on Si（111） substrates through ammoniating Ga2O3/ZnO films at 950℃. The as-grown products are characterized by x-ray diffraction （XRD）, scanning electron microscope （SEM）, field-emission transmission electron microscope （FETEM）, Fourier transform infrared spectrum （FTIR） and fluorescence spectrophotometer. The SEM images demonstrate that the products consist of flower-shape clustering GaN nanorods. The XRD indicates that the reflections of the samples can be indexed to the hexagonal GaN phase and HRTEM shows that the nanorods are of pure hexagonal GaN single crystal. The photoluminescence （PL） spectrum indicates that the GaN nanorods have a good emission property. The growth mechanism is also briefly discussed.     

Growth of Indium Nanorods by Magnetron Sputtering

Indium nanorods are grown on silicon substrates by using magnetron-sputtering technique. Film morphologies and nanorod microstructure are investigated by using scanning electron microscopy, high-resolution transmission electron microscopy （HRTEM）, and x-ray diffraction. It is found that the mean diameter of the nanorods ranges from 30nm to 100nm and the height ranges from 30nm to 200nm. The HRTEM investigations show that the indium nanorods are single crystals and grow along the [100] axis. The nanorods grow from the facets near the surface undulation that is caused by compressive stress in the indium grains generated during grain coalescence process. For low melting point and high diffusivity metal, such as bismuth and indium, this spontaneous nanorod growth mechanism can be used to fabricate nanostructures.     

Hybrid solar cell based on polythiophene and GaN nanoparticles composite

Hybrid solar cells based on poly(3-hexylthiophene)(P3HT)and Galium nitride(GaN)nanoparticle bulk heterojunction are fabricated and analyzed.The GaN nanocrystal is synthesized by means of a combination of sol–gel process with high temperature ammoniation using Ga(OC2H5)as a precursor.Their characteristics are determined by X-ray diffraction,X-ray photoelectron spectroscopy,and scanning electron microscopy.With the addition of GaN nanoparticle to P3HT,the device performance is greatly enhanced.