Gallium nitride nanowires doped with magnesium

GaN nanowires doped with Mg have been synthesized on Si (111) substrate through ammoniating Ga₂O₃ films doped with Mg under flowing ammonia atmosphere. The Mg-doped GaN nanowires were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL). The results demonstrate that the nanowires were single crystalline with hexagonal wurzite structure. The diameters of the nanowires ranged 20-30 nm and the lengths were about hundreds of micrometers. The intense PL peak at 359 nm showed a blueshift from the bulk band gap emission, attributed to Burstein-Moss effect. The growth mechanism of the crystalline GaN nanowires is discussed briefly.     

Synthesis of GaN nanowires through Ga2O3 films' reaction with ammonia

GaN nanowires were synthesized by ammoniating Ga₂O₃ films on Ti layers deposited on Si (111) substrates at 950 °C. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM). The XRD, FTIR and HRTEM studies showed that these nanowires were hexagonal GaN single crystals. SEM observation demonstrated that these GaN nanorods with diameters ranging from 50 nm to 100 nm and lengths up to several micrometers intervene with each other on the substrate.     

Synthesis of GaN nanorods by ammoniating Ga2O3 films on TiO2 (rutile) layer deposited on Si(111) substrates

GaN nanorods have been synthesized by ammoniating Ga₂O₃ films on a TiO₂ middle layer deposited on Si(111) substrates. The products were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformed infrared spectra (FTIR) and high-resolution transmission electron microscopy (HRTEM). The XRD analysis indicates that the crystallization of GaN film fabricated on TiO₂ middle layer is rather excellent. The FTIR, SEM and HRTEM demonstrate that these nanorods are hexagonal GaN and possess a rough morphology with a diameter ranging from 200 nm to 500 nm and a length less than 10 μm, the growth mechanism of crystalline GaN nanorods is discussed briefly.     

Synthesis and characterization of C3N4 nanowires and pseudocubic C3N4 polycrystalline nanoparticles

C₃N₄ nanowires and pseudocubic C₃N₄ polycrystalline nanoparticles have been synthesized by the reaction between C₃N₃Cl₃ and NaN₃ with Zn powder as catalyst. The process was carried out using a constant-pressure benzene thermal method at 40 MPa and 220 °C. The prepared nanowires have a diameter range of 3-6 nm and length range of 100-200 nm, while the diameters of the nanoparticles range from 10 nm to 40 nm. The as-prepared samples were characterized by X-ray powder diffraction (XRD), Fourier transform spectroscopy (FTIR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS).     

Fabrication of needle-shaped GaN nanowires by ammoniating Ga2O3 films on MgO layers deposited on Si (111) substrates

Needle-shaped GaN nanowires have been synthesized on Si (111) substrate through ammoniating Ga₂O₃/MgO films under flowing ammonia atmosphere at the temperature of 950 °C. The as-synthesized GaN nanowires were characterized by X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and high-resolution transmission electron microscopy (HRTEM). The results demonstrate that these nanowires are hexagonal GaN and possess a smooth surface with an average diameter about 200 nm and a length ranging from 5 μm to 15 μm. In addition, the diameters of these nanowires diminish gradually. The growth mechanism of crystalline GaN nanowires is discussed briefly.     

Preparation of Li2B4O7 thin films by chemical solution decomposition method

Li₂B₄O₇ polycrystalline films on silica glass and Si(111) substrates were prepared by chemical solution decomposition(CSD) method. After spin coating, the wet film was dried at 200 °C, and then annealed at different temperatures to form polycrystalline Li₂B₄O₇ film. These annealed films were characterized by using X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), transmission electron microscope (TEM) and selective area electron diffraction (SAED). All these results show that the main component of the film is Li₂B₄O₇ crystalline phase and the average crystalline size of these films is in the range of 20-50 nm.     

Effect of ammoniating temperature on morphologic and optical properties of GaN nanostructured materials

GaN nanostructured materials have been obtained on Si(111) substrates by ammoniating the Ga₂O₃/ZnO films at different temperature in a quartz tube. X-ray diffraction (XRD), Scanning electron microscope (SEM), and photoluminescence (PL) are used to analyze the structure, morphology and optical properties of GaN nanostructured films. The results show that their properties are investigated particularly as a function of ammoniating temperature. The optimally ammoniating temperature of Ga₂O₃ layer is 950 °C for the growth of GaN nanorods. These nanorods are pure hexagonal GaN wurtzite structure with lengths of about several micrometers and diameters of about 200 nm, which is conducive to the application of nanodevices. Finally, the growth mechanism is also briefly discussed.     

Controlled synthesis and characterization of 10 nm thick Al2O3 nanowires

α-Al₂O₃ nanowires, with diameter around 10 nm, were synthesized in bulk quantity by heating the mixture of pure aluminum and graphite powders at 900 °C. Scarcity of oxygen is regarded as the reason for the growth of the small diameter α-Al₂O₃ nanowires at relatively low temperature. The product was characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy and photoluminescence. The Oxygen vacancies in the nanowires lead to the strong photoluminescence in the wavelength range of 400-700 nm with its peak at 527 nm.     

Synthesis of single-crystal GaN nanowires on Si(111) substrate by ammonification technology

GaN nanowires have been synthesized on Si(111) substrate through ammoniating Ga₂O₃/BN films under flowing ammonia atmosphere at the temperature of 900 °C. The as-synthesized GaN nanowires were characterized by X-ray diffraction (XRD), selected-area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results demonstrated that the nanowires are hexagonal wurtzite GaN and possess a smooth surface with diameters ranging from 40 to 100 nm and lengths up to several tens of micrometers. The growth mechanism of crystalline GaN nanowires is discussed briefly.     

Synthesis and characterization of ?-Fe3N/GaN, 54/46-composite nanowires

?-Fe₃N/GaN, 54/46-composite nanowires (aspect ratio: 40), with core-shell structure, are synthesized by wet chemical method. Structural and morphological investigations are performed using X-ray diffraction (XRD)-Rietveld analysis and microscopy techniques. The encapsulation of ?-Fe₃N by GaN is probed by X-ray photoelectron spectroscopy (XPS). The in-depth profile analysis probes the large interface region consisting both the phases. Although the respective surface oxynitride phases are present, the nitride phases are dominant inside the nanowires. The interface region of the nanowires influences the low temperature magnetic behavior. The superparamagnetic and ferromagnetic fractions coexist even at 5 K, due to the nanowire size distribution. Spin-glass-like collective ordering is observed below 50 K due to the freezing of the localized frustrated spins. Room temperature photoluminescence (PL) reveals the presence of surface states in the GaN shell.     

The preparation,characterization and optical properties of Cd2V2O7 and CdCO3 compounds

Cadmium vanadium oxides (Cd₂V₂O₇) and Cadmium carbonates (CdCO₃) were synthesized via a facile hydrothermal method. X-ray diffraction (XRD), Raman spectroscopy, infrared spectrometer (IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the structure, morphology and chemical state of the samples, respectively. The photoluminescence (PL) properties of the as-synthesized Cd₂V₂O₇ and CdCO₃ were measured at room temperature using an excitation wavelength of 325 nm. The Cd₂V₂O₇ shows two visible light emission centers located at 589 and 637 nm, which are supposed to be relevant to local defects in Cd₂V₂O₇. The CdCO₃ shows three emission centers located at 408, 530 and 708 nm, which are supposed to be relevant to the electron transition from the conduction band to valence band and defect related energy level.     

Ultraviolet photodetectors made from SnO2 nanowires

SnO₂ nanowires can be synthesized on alumina substrates and formed into an ultraviolet (UV) photodetector. The photoelectric current of the SnO₂ nanowires exhibited a rapid photo-response as a UV lamp was switched on and off. The ratio of UV-exposed current to dark current has been investigated. The SnO₂ nanowires were synthesized by a vapor-liquid-solid process at a temperature of 900 °C. It was found that the nanowires were around 70-100 nm in diameter and several hundred microns in length. High-resolution transmission electron microscopy (HRTEM) image indicated that the nanowires grew along the [200] axis as a single crystallinity. Cathodoluminescence (CL), thin-film X-ray diffractometry, and X-ray photoelectron spectroscopy (XPS) were used to characterize the as-synthesized nanowires.     

Self-catalytic formation and characterization of Zn2SnO4 nanowires

Mass production of transparent semiconducting ternary oxide Zn₂SnO₄ nanowires is successfully synthesized by the thermal evaporation method without any catalyst. The as-synthesized products are characterized with field-emission scanning electron microscope (FE-SEM), X-ray powder diffraction (XRD), energy-dispersive spectroscopy (EDS), high-resolution transmission electron microscope (HR-TEM) and selected area electron diffraction (SEAD). A formation of Zn₂SnO₄ nanowires based on a self-catalytic VLS growth mechanism is discussed. The photoluminescence spectrum (PL) of the nanowires shows a broad blue-green emission around the 300-600 nm wavelengths with a maximum center at 580 nm under room temperature.     

Deposition of ZnO thin films on SiO2/Si substrate with Al2O3 buffer layer by radio frequency magnetron sputtering for high frequency surface acoustic wave devices

ZnO films with c-axis (0002) orientation have been grown on SiO₂/Si substrates with an Al₂O₃ buffer layer by radio frequency magnetron sputtering. Crystalline structures of the films were investigated by X-ray diffraction, atomic force microscopy and scanning electron microscopy. The center frequency of the surface acoustic wave (SAW) device with a 4.8 μm thick Al₂O₃ buffer layer was measured to be about 408 MHz, which was much higher than that (265 MHz) of ZnO/SiO₂/Si structure and approaches that (435 MHz) of ZnO/sapphire. It is a possible way as an alternative for the sapphire substrate for the high frequency SAW device applications, and is also useful to integrate the semiconductor and high frequency SAW devices on the same Si substrate.     

Synthesis of GaPO4-GaN Coaxial Nanowires

GaPO₄-GaN coaxial nanowires were synthesized by two-step chemical vapor deposition method using H₂ and NH₃ as reactant gas in turn at 950°C. The morphology and microstructures of the GaPO4-GaN coaxial nanowires were studied by scanning elctron microscopy (SEM), X-ray diffraction (XRD) and transmission lectron microscopy (TEM). The nanowires have an average diameter of ~15 nm and length of hundreds of anometers. The core is GaPO₄ crystal and the outer shell is GaN crystal. The formation mechanism was iscussed and the key factors controlling the growth are temperature and the concentration of reactant gases. hese coaxial nanowires may have potential application for piezoluminescence nano-devices, and the two-step ynthetic technique could be used to grow rationally other 1D GaN-based nanowire heterostructures.     

Building crystalline Sb2S3 nanowire dandelions with multiple crystal splitting motif

Crystalline dandelion-like antimony (III) sulfide (Sb₂S₃) nanowires were synthesized by a PEG-assisted solvothermal process. The orthorhombic crystal structure and dandelion-like multi-branched nanowire morphology were revealed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM) respectively. High-resolution transmission electron microscopy (TEM) identified that the highly crystalline Sb₂S₃ nanowires grew along the [001] direction with individual wire diameter of 195 ± 52 nm. The band gap of the Sb₂S₃ nanowires was measured to be ca. 1.67 eV. A combination of PEG-templated assembly and crystal splitting mechanism was likely responsible for the growth of the observed nanowire dandelion structures.     

Preparation and luminescence properties of Mn-doped ZnGa2O4 nanofibers via electrospinning process

One-dimensional Mn²⁺-doped ZnGa₂O₄ nanofibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. SEM results indicated that the as-formed precursor fibers and those annealed at 700 °C are uniform with length of several tens to hundred micrometers, and the diameters of the fibers decrease greatly after being heated at 700 °C. Under ultraviolet excitation (246 nm) and low-voltage electron beams (1–3 kV) excitation, the ZnGa₂O₄:Mn²⁺ nanofibers presents the blue emission band of the ZnGa₂O₄ host lattice and the strong green emission with a peak at 505 nm corresponding to the ⁴T₁–⁶A₁ transition of Mn²⁺ ion.     

Multifunctional Zn0.99−xMn0.01CuxS nanowires: Structure, luminescence and magnetism

The wurtzite-type Zn_0.99−xMn_0.01Cu_xS (x = 0, 0.003, 0.01) nanowires were prepared by a simple hydrothermal method at 180 °C. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron micrograph (FESEM) and X-ray photoelectron spectrum (XPS). The results showed that both the Mn²⁺ and Cu²⁺ ions substituted for the Zn²⁺ sites in the host ZnS. The ethylenediamine-mediated template was observed, which was used to explain the growth mechanism of the nanowires. The color-tunable emission can be obtained by adjusting the concentrations of Mn²⁺ and Cu²⁺ ions. The ferromagnetism was observed around room temperature.     

Synthesies and properties of Tb-doped GaN nanowires

The synthesis of Tb-doped GaN nanowires on Si (111) substrates through ammoniating Ga₂O₃ films doped with Tb was investigated. X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy and photoluminescence were used to characterize the composition, structure, morphology and optical properties of the products. The results show that the as-synthesized GaN nanowires doped with 3 at % Tb are of single-crystalline hexagonal wurtzite structure. The nanowires have diameters ranging from 30 to 50 nm and the lengths up to tens of micrometers. An f-f intra-atomic transition of rare earth at 545 nm corresponding to ⁵ D ₄–⁷ F ₅ of the Tb³⁺ and other two peaks related with doping are observed in PL spectrum, confirming the doping of Tb into GaN. The growth mechanism of GaN nanowires was discussed briefly.     

Control of growth orientation and shape for epitaxially grown In2O3 nanowires on a-plane sapphire

Vertically aligned indium oxide nanowires were grown on a-plane sapphire substrate by the method of catalyst-assisted carbothermal reduction. The morphology and crystal structure of the nanowires are determined by X-ray diffraction, transmission electron microscopy and field-emission scanning electron microscopy. Two types of In₂O₃ nanowires were found by controlling the growth conditions. The nanowires with a hexagonal cross-section were shown to grow in [1 1 1] direction, whereas those with a square cross-section grow in [0 0 1] direction. In addition to the temperature effects, the concept of supersaturation in Au catalyst is proposed to explain the formation of these two types of nanowires. Besides, tapering, which is explained with the interplay between the vapor-liquid-solid and vapor-solid growth mechanisms, is observed in the nanowires.