Au-catalysed free-standing wurtzite structured InAs nanosheets grown by molecular beam epitaxy

In this study,we report the growth of free-standing InAs nanosheets using Au catalysts in molecular beam epitaxy.Detailed structural characterizations suggest that wurtzite structured InAs nanosheets,with features of extensive{1120}surfaces,grown along the<1102>direction and adopted{0001}nanosheet/catalyst interfaces,are initiated from wurtzite structured[0001]nanowires as the inclined epitaxial growth due to relatively higher In concentrations in Au catalysts,and grown from these inclined nanostructures through catalyst-induced axial growth and their enhanced lateral growth under the high growth temperature.Based on the facts that the nanosheets contain large low energy{1120}surfaces and{0001}nanosheet/catalyst interfaces,the growth of our nanosheets is a thermodynamically driven process.This study provides new insights into fabricating free-standing Ⅲ-Ⅴ nanosheets for their applications in future nanoscale devices.

A Molecular Dynamics Study on the (1120) Domain Boundary Structures in Epitaxial Wurtzite GaN

A computer program has been developed for the moIlcular dynamics calculation of ionic orstrong-ionic covalent systems. Ewald summation algorithm and Keating potentiaI model areadopted to calculate the long-range Coulomb interaction and the short-range bonding forces,respectively. A theoretical study on the domain boundary structures in epitaxial wurtzite GaN film is accomplished with the program. The calculation result is used in the structure formationexplanation of an interesting defect observed by HREM experiment.

Effect of substrate temperature on microstructural and optical properties of ZnO films grown by pulsed laser deposition

ZnO thin films were deposited on n-Si （111） at various substrate temperatures by pulsed laser deposition （PLD）. X-ray diffraction （XRD）, photoluminescence （PL）, Fourier transform infrared spectrophotometer （FTIR）, and scanning electron microscopy （SEM） were used to analyze the structure, morphology, and optical property of the ZnO thin films. An optimal crystallized ZnO thin film was obtained at the substrate temperature of 600℃. A blue shift was found in PL spectra due to size confinement effect as the grain sizes decreased. The surfaces of the ZnO thin films were more planar and compact as the substrate temperature increased.

Formation of GaN Nanowires by Ammoniating Ga_2O_3 Films Deposited on Oxidized Al Layers on Si Substrate

Large quantities of gallium nitride(GaN) nanowires have been prepared via ammoniating the Ga2O3 films deposited on the oxidized aluminum layer at 950 ℃ in a quartz tube. The nanowires have been confirmed as crystalline wurtzite GaN by X-ray diffraction, X-ray photoelectron spectrometry scanning electron microscope and selected-area electron diffraction. Transmission electron microscope(TEM) and scanning electron microscopy(SEM) reveal that the nanowires are amorphous and irregular, with diameters ranging from 30 nm to 80 nm and lengths up to tens of microns. Selected-area electron diffraction indicates that the nanowire with the hexagonal wurtzite structure is the single crystalline. The growth mechanism is discussed briefly.

Preparation and characterization of ultrafine zinc oxide powder by hydrothermal method

With Zinc acetate and sodium hydroxide as raw materials,while polyethylene glycol employed as dispersant agent, ultrafine zinc oxide powder was synthesized by hydrothermal method.Influence of NaOH concentration on morphology of ZnO powder was studied.The as-synthesized ZnO powder looked like flower cluster and consisted of microrods with hexagonal morphologies.The crystal structure and optical property of the as-prepared powder were also characterized using XRD,UV-visible absorption spectrum and photoluminescence spectrum.The results indicate that ZnO powder is of hexagonal wurtzite structure and well crystallized with high purity.There is a strong excitation absorption peak at 300 nm in UV-visible absorption spectrum and blue shift exists obviously.The optical property of ZnO powder is excellent.

Shape-controllable Synthesis of Ultrafine ZnO Powders of Different Morphologies

By employing zinc acetate and sodium hydroxide as raw materials, ultrafine ZnO powders with different morphologies were successfully synthesized through hydrothermal method. The influences of the reaction temperature, the OH-/Zn2＋ mol ratio and the reaction time on the morphologies of the ZnO powders were discussed. The reaction conditions were obtained, under which the ZnO of flower-like particles, micro-rods and flake particles was synthesized, respectively. The crystal structures and morphologies of those ZnO particles were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The ZnO with flower-like structures was composed of lots of micro-rods with hexagon morphology. The XRD patterns indicated that the ZnO powders were hexagonal wurtzite structures with high purity. Finally, the growth mechanism of the ZnO particles was discussed.