Spinel-type ZnSb<Subscript>2</Subscript>O<Subscript>4</Subscript> nanowires and nanobelts synthesized by an indirect thermal evaporation

Uniform zinc antimoniate (ZnSb₂O₄) nanowires and nanobelts with a spinel structure were synthesized by an indirect thermal evaporation method in air. The as-synthesized ZnSb₂O₄ nanowires and nanobelts are single crystalline, usually several tens of microns in length. The diameter of the nanowires is about 20 nm; the thickness and the width of the nanobelts are about 15 nm and 60 nm, respectively. Most of the nanowires and nanobelts grow along the [001] direction. A possible formation mechanism is also proposed to account for the growth of these ZnSb₂O₄ nanobelts and nanowires. PACS 61.46.+w; 81.07.-b     

Electrical and photocatalytic properties of Na2Ti6O13 nanobelts prepared by molten salt synthesis

Single-crystalline Na₂Ti₆O₁₃ nanobelts were prepared on large-scale by molten salt synthesis at 825 °C for 3 h. The obtained nanobelts have typical width of less than 200 nm and thickness of 10-30 nm, and length up to 10 μm. The growth direction of the nanobelts was determined to be along [0 1 0]. Electrical transport property of an individual nanobelt was measured at room temperature and ambient atmosphere, and results showed that the nanobelts are semiconductor. Na₂Ti₆O₁₃ nanobelts exhibited good photocatalytic efficiency for the degradation of RhB under UV irradiation.     

Structure and NO2 gas sensing properties of SnO2-core/In2O3-shell nanobelts

SnO₂-core/In₂O₃-shell nanobelts were fabricated by a two-step process comprising thermal evaporation of Sn powders and sputter-deposition of In₂O₃. Transmission electron microscopy and X-ray diffraction analyses revealed that the core of a typical core–shell nanobelt comprised a simple tetragonal-structured single crystal SnO₂ and that the shell comprised an amorphous In₂O₃. Multiple networked SnO₂-core/In₂O₃-shell nanobelt sensors showed the response of 5.35% at a NO₂ concentration of 10 ppm at 300 °C. This response value is more than three times larger than that of bare-SnO₂ nanobelt sensors at the same NO₂ concentration. The enhancement in the sensitivity of SnO₂ nanobelts to NO₂ gas by sheathing the nanobelts with In₂O₃ can be accounted for by the modulation of electron transport by the In₂O₃–In₂O₃ homojunction.     

Control synthesis of octahedral In2O3 crystals,belts, and nanowires

Octahedral In₂O₃ crystals were synthesized by evaporation of a mixture of In₂O₃ and graphite in a horizontal double-tube system. By adjusting the experimental conditions, In₂O₃ nanowires and nanobelts were also obtained. The microstructures of the resultant In₂O₃ materials were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), X-ray diffraction. In addition, the growth mechanism of the octahedral In₂O₃ crystals was discussed in detail.     

Indium oxide nanostructures

In this report we review the growth of indium oxide (In₂O₃) nanostructures, including octahedral nanocrystals (NCs), nanobelts (NBs), nanosheets (NSs), and nanowires (NWs), by hot-wall chemical vapor deposition (HW-CVD). This system is highly controllable, allowing the user to easily access different growth regimes – each corresponding to the growth of a different nanostructure – by changing growth variables of the HW-CVD system. Hot-wall CVD produces crystalline nanostructures; here we present a survey of microstructural characterizations of the four types of In₂O₃ nanostructures using transmission- and scanning-electron microscopy. Interestingly, the In₂O₃ nanostructures have different preferred growth directions: NCs have (111) faces, NBs are predominantly (200), and NWs are predominantly (110). We end the review by discussing the current shortcomings of HW-CVD growth of In₂O₃ nanostructures. PACS 61.46.-w; 61.82.Rx; 73.31.Hb; 81.02.-b     

Hydrothermal synthesis of ZnO nanobelts and gas sensitivity property

The ZnO nanobelts were synthesized by a hydrothermal method. The XRD spectrum indicates that the sample is wurtzite (hexagonal) structured ZnO with lattice constants of , . SEM and TEM images show the nanobelts to have lengths of 10-20 μm, widths of 50-500 nm, thicknesses of about 30-60 nm, and growth direction of [0001]. Gas sensitivity experiments on ZnO nanobelts were carried out under different temperatures. The results indicated high sensitivities with an operating temperature of only 220 ^°C for the oxidative gas O₂, and 305 ^°C for the gas N₂. The mechanism of gas sensitive effects is analyzed in detail.     

Synthesis and characterization of nitrogen-rich carbon nitride nanobelts by pyrolysis of melamine

Nitrogen-rich g-C₃N₄ nanobelts were successfully synthesized via pyrolysis of melamine (C₃N₆H₆). The as-synthesized nanobelts are structurally uniform, and each belt is uniform in width and thickness along its length direction. The typical width is in the range of 600 nm and 1.5 μm, respectively. The typical length of belts is in the range of several hundreds of micrometers; some of them even have lengths on the order of millimeters. The structure and morphology were researched by XRD, SEM, TEM, CEA, XPS, FTIR, and TG measurements. The theoretical FTIR spectra are calculated to compare with experiment value. It is found that the NH₂ edges in the nanobelts are precisely for the reason of rich nitrogen. The photoluminescence (PL) spectrum was carried out. Two peaks at 443 and 500 nm were observed in the spectrum. In addition, a possible growth mechanism is also inferred by principle of VLS.     

Synthesis of beta-gallium oxide nanobelts through microwave plasma chemical vapor deposition

Beta-gallium oxide (β-Ga₂O₃) nanobelts were synthesized through microwave plasma chemical vapor deposition (MPCVD) of liquid-phase gallium containing H₂O in Ar atmosphere using silicon as the substrate. Unlike the common microwave plasma method, the H₂O, not mixture of the gas, was employed to synthesize the nanostructures. β-Ga₂O₃ nanobelts prepared by MPCVD have not been reported. The thickness of β-Ga₂O₃ nonobelts was 20–30 nm and length of them was tens to hundreds of microns. The morphology and structure of the products were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Possible growth mechanisms of the β-Ga₂O₃ nanobelts are briefly discussed.     

Hydrothermal synthesis of mesoporous Co3O4 nanobelts by means of a compound precursor

In the present work, high surface area mesoporous cobalt oxide (Co₃O₄) nanobelts have been synthesized by thermal treatment of cobalt hydroxide carbonate (CHC) precursors. CHC nanobelts were prepared by a facile hydrothermal method. Control experiments with variations in reaction time, solvent and different cobalt source revealed that temperature and sulfates are key factors in determining the formation of CHC nanobelts. Scanning electron microscopy and transmission electron microscopy images showed that the Co₃O₄ nanobelts consisted of mesoporous nanobelts with the average width of 40 nm. Brunauer–Emmett–Teller (BET) gas adsorption measurement further indicated that the products presented a rather large surface area (172.09 m² g^?1).     

Structural and catalytic properties of ZnO and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanostructures loaded with metal nanoparticles

Nanostructured zinc oxide (ZnO) nanobelts and aluminum oxide (Al₂O₃) nanoribbons have been grown successfully from the vapor phase. XRD results confirmed the purity and the high quality of the formed crystalline materials. TEM images showed that ZnO nanostructures grew in the commonly known tetrapod structure with nanobelts separated from the tetrapods with an average width range of 10–30 nm and a length of about 500 nm. Al₂O₃ nanostructures grew in the form of nanoribbons with an average width range of 20–30 nm and a length of up to 1 μm. The catalytic oxidation of CO gas into CO₂ gas over the synthesized nanostructures is also reported. Higher catalytic activity was observed for Pd nanoparticles loaded on the ZnO nanobelts (100% conversion at 270 °C) and Al₂O₃ nanoribbons (100% conversion at 250 °C). The catalytic activity increased in the order Cu < Co < Au < Pd for the metal-loaded nanostructures. The preparation methods could be applied for the synthesis of novel nanostructures of various materials with novel properties resulting from the different shapes and morphologies.     

Tunable growth of (GaxIn1−x)2O3 nanowires by water vapor

The tunable growth of In-doped Ga₂O₃ (Ga₂O₃:In) and Ga-doped In₂O₃ (In₂O₃:Ga) nanowires (NWs) on Au-coated Si substrates was achieved by modulating the amount of water vapor in flowing Ar at 700–750 °C via carbothermal reduction of Ga₂O₃/In₂O₃ powders with a fixed weight ratio. In Ar, only the Ga₂O₃:In NWs were grown, while in wet Ar the In₂O₃:Ga NWs were synthesized instead. The Ga concentration in In₂O₃ NWs decreased with the increment of water vapor in flowing Ar. The growth of both Ga₂O₃:In and In₂O₃:Ga NWs followed the vapor–liquid–solid process. The In and Ga doping induced a redshift and a blueshift in the optical bandgaps of Ga₂O₃ NWs and In₂O₃ NWs, respectively. The growth mechanisms and optical properties of Ga₂O₃:In and In₂O₃:Ga NWs were discussed.     

Temperature-controlled synthesis of Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> nanobelts and nanosheets

We have investigated the effect of growth temperature on structural morphology and photoluminescence (PL) properties of as-synthesized gallium oxide (Ga₂O₃) nanostructures. The products consisted of Ga₂O₃ nanobelts and nanosheets (i.e. wider nanobelts), which had monoclinic crystalline structures. The average width of structures grown at 1000 °C was relatively greater than those at 800 °C, revealing that higher temperature favored the formation of nanosheets. PL measurements of 800 °C- and 1000 °C-grown samples indicated that both samples exhibited a broad emission band peaked around the blue-light region, while only the 800 °C-grown sample showed a red peak. PACS 81.07.-b; 81.05.Je; 61.10.Nz; 68.37.Hk; 68.37.Lp     

Hydrothermal synthesis and electrochemical properties of α-MoO3 nanobelts used as cathode materials for Li-ion batteries

Uniform α-MoO₃ nanobelts were successfully synthesized by the hydrothermal process at 180°C for 20 h of the acidic solutions with different pH values of 0–0.75, adjusted using HCl (conc.). XRD and SEM results revealed that the pH of the precursor solutions played an important role in the phase, impurities, and morphology of the products. At the pH=0, the perfect α-MoO₃ nanobelts with a few tens of microns long were synthesized. By the TEM characterization, orthorhombic MoO₃ has a distinctive layered structure along the [010] direction, consisting of distorted MoO₆ octahedrons connected by common corners along the [100] direction and common edges along the [001] direction. The electrochemical measurement showed that the α-MoO₃ nanobelts have high specific charge capacity.     

Co-doped In2O3 thin films: Room temperature ferromagnets

Laser-ablated Co-doped In₂O₃ thin films were fabricated under various growth conditions on R-cut Al₂O₃ and MgO substrates. All Co:In₂O₃ films are well-crystallized, single phase, and room temperature ferromagnetic. Co atoms were well substituted for In atoms, and their distribution is greatly uniform over the whole thickness of the films. Films grown at 550 °C showed the largest magnetic moment of about 0.5 μ_B/Co, while films grown at higher temperatures have magnetic moments of one order smaller. The observed ferromagnetism above room temperature in Co:In₂O₃ thin films has confirmed that doping few percent of magnetic elements such as Co into In₂O₃ could result in a promising magnetic material.     

Synthesis,structural and ellipsometric evaluation of oxygen-deficient and nearly stoichiometric zinc oxide and indium oxide nanowires/nanoparticles

Oxygen-deficient (OD) and nearly stoichiometric (NST) ZnO and In₂O₃ nanowires/nanoparticles were synthesized by chemical vapor deposition on Au-coated silicon substrates. The OD ZnO and OD In₂O₃ nanowires were synthesized at 750 and 950°C, respectively, using Ar flow at ambient pressure. A mixture of flowing Ar and O₂ was used for synthesizing NST ZnO nanowires and NST In₂O₃ nanoparticles. Growth of OD ZnO nanowires and NST In₂O₃ nanoparticles was found to be via a vapor–solid (VS) mechanism and the growth of NST ZnO nanowires was via a vapor–liquid–solid mechanism (VLS). However, it was uncertain whether the growth of OD In₂O₃ nanowires was via a VS or VLS mechanism. The optical constants, thickness and surface roughness of the prepared nanostructured films were determined by spectroscopic ellipsometry measurements. A three-layered model was used to fit the calculated data to the experimental ellipsometric spectra. The refractive index of OD ZnO, NST ZnO nanowires and NST In₂O₃ nanoparticles films displayed normal dispersion behavior. The calculated optical band gap values for OD ZnO, NST ZnO, OD In₂O₃ nanowires and NST In₂O₃ nanoparticles films were 3.03, 3.55, 2.81 and 3.52?eV, respectively.     

Characterization of interface between CuInSe2 and In2O3

CuInSe₂/In₂O₃ structures were formed by depositing CuInSe₂ films by stepwise flash evaporation onto In₂O₃ films, which were grown by DC reactive sputtering of In target in presence of (Ar+O₂) gas mixture. Phase purity of the CuInSe₂ and In₂O₃ films was confirmed by Transmission Electron Microscopy (TEM) studies. X-ray diffraction (XRD) results on CuInSe₂/In₂O₃/glass structures showed sharp peaks corresponding to (112) plane of CuInSe₂ and (222) plane of In₂O_3. Rutherford Backscattering Spectrometry (RBS) investigations were carried out on CuInSe₂/In₂O₃/Si structures in order to characterize the interface between In₂O₃ and CuInSe₂. The results show that the CuInSe₂ films were near stoichoimetric and In₂O₃ films had oxygen deficient composition. CuInSe₂/In₂O₃ interface was found to include a ∼20 nm thick region consisting of copper, indium and oxygen. Also, the In₂O₃/Si interface showed the formation of ∼20 nm thick region consisting of silicon, indium and oxygen. The results are explained on the basis of diffusion/reaction taking place at the respective interfaces.     

大面积α-Fe2O3纳米线及纳米带阵列的制备研究

以铁箔为原材料和基片,通过控制热氧化过程中的宏观实验条件(载气流量及其组分、压强、温度分布和反应时间等),实现了α-Fe₂O₃一维纳米结构的可控生长,获得了大面积(10mm×10mm)、单分散性好、沿［110］方向生长的α-Fe₂O₃纳米带或纳米线阵列. 对不同宏观实验条件下所制备的样品进行形貌和晶格结构表征和分析,认为热氧化过程中α-Fe₂O₃一维纳米结构的生长遵循类似气- 关键词： 2O₃')" href="#">α-Fe₂O₃ 一维纳米结构 热氧化法     

Structural and optical properties of glancing angle deposited In2O3 columnar arrays and Si/In2O3 photodetector

Ordered and perpendicular columnar arrays of In₂O₃ were synthesized on conducting ITO electrode by a simple glancing angle deposition (GLAD) technique. The as-deposited In₂O₃ columns were investigated by field emission gun-scanning electron microscope (FEG-SEM). The average length and diameter of the columns were estimated ～400 nm and ～100 nm, respectively. The morphology of the structure was examined by transmission electron microscopy (TEM). X-ray diffraction (XRD) analysis shows the polycrystalline nature of the sample which was verified by selective area electron diffraction (SAED) analysis. The growth mechanism and optical properties of the columns were also discussed. Optical absorption shows that In₂O₃ columns have a high band to band transition at ～3.75 eV. The ultraviolet and green emissions were obtained from the In₂O₃ columnar arrays. The P-N junction was formed between In₂O₃ and P-type Si substrate. The GLAD synthesized In₂O₃ film exhibits low current conduction compared to In₂O₃ TF. However, the Si/GLAD-In₂O₃ detector shows ～1.5 times enhanced photoresponsivity than that of Si/In₂O₃ TF.     

Search for new transparent conductors: Effect of Ge doping on the conductivity of Ga2O3, In2O3 and Ga1.4In0.6O3

Only a small amount (≤3.5 mol%) of Ge can be doped in Ga₂O₃, Ga_1.4In_0.6O₃ and In₂O₃ by means of solid state reactions at 1400 °C. All these samples are optically transparent in the visible range, but Ge-doped Ga₂O₃ and Ga_1.4In_0.6O₃ are insulating. Only Ge-doped In₂O₃ exhibits a significant decrease in resistivity, the resistivity decreasing further on thermal quenching and H₂ reduction. The resistivity of 2.7% Ge-doped In₂O₃ after H₂ reduction shows a metallic behavior, and a resistivity of ～1 mΩ cm at room temperature, comparable to that of Sn-doped In₂O₃.     

Structural and optical properties of Ga2(1−x)In2xO3 films prepared on α-Al2O3 (0 0 0 1) by MOCVD

Ga_2(1−x)In_2xO₃ thin films with different indium content x [In/(Ga + In) atomic ratio] were prepared on α-Al₂O₃ (0 0 0 1) substrates by the metal organic chemical vapor deposition (MOCVD). The structural and optical properties of the Ga_2(1−x)In_2xO₃ films were investigated in detail. Microstructure analysis revealed that the film deposited with composition x = 0.2 was polycrystalline structure and the sample prepared with x up to 0.8 exhibited single crystalline structure of In₂O₃. The optical band gap of the films varied with increasing Ga content from 3.72 to 4.58 eV. The average transmittance for the films in the visible range was over 90%.