Growth mechanism and photoluminescence of the SnO2 nanotwists on thin film and the SnO2 short nanowires on nanorods

SnO2 nanotwists on thin film and SnO2 short nanowires on nanorods have been grown on single silicon substrates by using Au-Ag alloying catalyst assisted carbothermal evaporation of SnO2 and active carbon powders.The morphology and the structure of the prepared nanostructures are determined on the basis of field-emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),selected area electronic diffraction(SAED),high-resolution transmission electron microscopy(HRTEM),x-ray diffraction(XRD),Raman and photoluminescence(PL) spectra analysis.The new peaks at 356,450,and 489 nm in the measured PL spectra of two kinds of SnO2 nanostructures are observed,implying that more luminescence centres exist in these SnO2 nanostructures due to nanocrystals and defects.The growth mechanism of these nanostructures belongs to the vapour-liquid-solid(VLS) mechanism.     

Structure Properties of MgxZn1-xO Films Deposited at Low Temperature

MgxZn1-xO films (x = 0.23) have been prepared on silicon substrates by radio-frequency magnetron sputtering at 80℃. The structure properties of Mgx Zn1-xO films are studied using x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy and Raman spectra. The analysis of XRD and HRTEM indicates that the Mgx Zn1-xO films have hexagonal wurtzite single-phase structures and a preferred orientation with the c axis perpendicular to the substrates. Raman spectra of ZnO and MgxZn1-xO films reveal that the MgxZn1-xO films have not only the hexagonal wurtzite structure but also higher crystalline quality than ZnO films.     

Superconductivity of Bi1.6Pb0.4Sr2Ca3Cu4O12

The superconducting ceramics Bi1.6Pb0.4Sr2Ca3Cu4O12 have been prepared by the melt-casting method.A zero resistance temperature at 60K has been observed.It has been found that the superconducting phase temperature Tc increases with increasing sintering temperature,The effect of Pb content on the superconductivity of the ceramic has been studied.The microstructure of the Sample has been investigated by scanning electron microscopy.Phase analysis has been carried out by x-ray diffraction patterns and energy dispersive analysis through x-ray spectroscopy.     

Single crystalline boron carbide nanobelts: synthesis and characterization

This paper reports that the large-scale single crystalline boron carbide nanobelts have been fabricated through a simple carbothermal reduction method with B/B2O3/C/Fe powder as precursors at 1100℃. Transmission electron microscopy and selected area electron diffraction characterizations show that the boron carbide nanobelt has a B4C rhomb-centred hexagonal structure with good crystallization. Electron energy loss spectroscopy analysis indicates that the nanobelt contains only B and C, and the atomic ratio of B to C is close to 4：1. High resolution transmission electron microscopy results show that the preferential growth direction of the nanobelt is [101]. A possible growth mechanism is also 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.     

Microstructural and electromagnetic properties of MnO2 coated nickel particles with submicron size

Nickel particles with submicron size are prepared by using the solvothermal method. These spheres are then coated with a layer of MnO2 using the soft chemical method. The microstructure is characterized by x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Energy x-ray dispersive spectrometry and high-resolution images show that the granular composites have a classical core/shell structure with an MnO2 superficial layer,no more than 10 nm in thickness. The hysteresis measurements indicate that these submicron-size Ni composite powders have small remanence and moderate coercivity. The electromagnetic properties of the powders measured by a vector network analyzer in a frequency range of 2-18 GHz are also reported in detail.     

Laser Molecular Beam Epitaxy Growth of BaTiO3 in Seven Thousands of Unit-Cell Layers

BaTiO3 thin films in seven thousands of unit-cell layers have been successfully fabricated on SrTiO3 （001） substrates by laser molecular beam epitaxy. The fine streak pattern and the undamping intensity oscillation of reflection high-energy electron diffraction indicate that the BaTiO3 film was layer-by-layer epitaxial growth. The measurements of scanning electron microscopy and atomic force microscopy show that surfaces of the BaTiO3 thin film are atomically smooth. The measurements of x-ray diffraction and transmission electron microscopy, as well as selected-area electron diffraction reveal that the BaTiO3 thin film is a c-oriented epitaxial crystalline structure.     

Canted antiferromagnetic and optical properties of nanostructures of Mn2O3 prepared by hydrothermal synthesis

We have reported new magnetic and optical properties of Mn2O3 nanostructures.The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system.The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) analysis,transmission electron microscopy(TEM),high resolution transmission electron microscopy(HRTEM),Raman spectroscopy(RS),UV-visible spectroscopy,and the vibrating sample magnetometer(VSM).Structural investigation manifests that the synthesized Mn2O3 nanostructures are orthorhombic crystal.Magnetic investigation indicates that the Mn2O3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at TN=83 K.Furthermore,the Mn2O3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration,resulting in hysteresis with large coercivity(1580 Oe) and remnant magnetization(1.52 emu/g).The UV-visible spectrophotometry was used to determine the transmittance behaviour of Mn2O3 nanostructures.A direct optical band gap of 1.2 eV was acquired by using the Davis-Mott model.The UV-visible spectrum indicates that the absorption is prominent in the visible region,and transparency is more than 80% in the UV region.     

Preparation and NO_2-gas sensing property of individual β-Ga_2O_3 nanobelt

Monoclinic gallium oxide (β-Ga_2O_3) nanobelts are synthesized from gallium and oxygen by thermal evaporation in an argon atmosphere and their NO_2 sensing properties are studied at room temperature.Electron microscopy studies show that the nanobelts have breadths ranging from 30 to 50 nm and lengths up to tens of micrometers.Both the x-ray diffraction (XRD) and the selected are electron diffraction (SAED) examinations indicate that β-Ga_2O_3 nanobelts have grown into single crystals.Room temperature NO_2 sensing tests show that the current of individual β-Ga_2O_3 nanobelt decreases quickly,and then gently when the NO_2 concentration increases from low to high.It is caused by the NO_2 molecule chemisorption and desorption processes in the surface of β-Ga_2O_3 nanobelt.     

Structures and magnetic anisotropy of β-Mn2V2O7 crystals synthesized by the molten salt method

β-Mn2V2O7 crystals with strip shape are successfully prepared by the molten salt method in a closed crucible,and are characterized by x-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM),selected area of electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM).The results indicate that the sample is of the β-Mn2V2O7 crystal with monoclinic symmetry,level natural cleavage facets and directional growth.Magnetic properties are measured by vibration sample magnetometry (VSM) at room temperature,and the magnetic hysteresis loop indicates that the β-Mn2V2O7 has anti-ferromagnetic properties with low coercive force and remnant magnetization.The magnetic measurement results in different directions exhibit that the β-Mn2V2O7 has magnetic anisotropy,which is due to the fact that the magnetic interaction energy of the β-Mn2V2O7 is lowest only when the electron configuration is in a certain direction.