Correlation of Morphology Evolution with Carrier Dynamics in InN Films Heteroepitaxially Grown by MOMBE

In this study, we report the catalyst-free growth of n-type wurtzite InN, along with its optical properties and carrier dynamics of different surface dimensionalities. The self-catalyzed epitaxial growth of InN nanorods grown by metal–organic molecular-beam epitaxy on GaN/Al2O3(0001) substrates has been demonstrated. The substrate temperature is dominant in controlling the growth of nanorods. A dramatic morphological change from 2D-like to 1D nanorods occurs with decreasing growth temperature. The InN nanorods have a low dislocation density and good crystalline quality, compared with InN films. In terms of optical properties, the nanorod structure exhibits strong recombination of Mahan excitons in luminescence, and an obvious spatial correlation effect in phonon dispersion. The downward band structure at the nanorod surface leads to the photon energy-dependent lifetime being upshifted to the high-energy side.

Rapid growth of a long-seed KDP crystal

To reduce the seed length while maintaining the advantages of the cuboid KDP-type crystal, a long-seed KDP crystal with size $471~\text{mm}\times 480~\text{mm}\times 400~\text{mm}$ is rapidly grown. With almost the same high cutting efficiency to obtain third harmonic generation oriented samples, this long-seed KDP-type crystal can be grown with a shorter seed than that of the cuboid KDP-type crystal. The full width at half maximum of the high-resolution X-ray diffraction of the (200) crystalline face is 28.8 arc seconds, indicating that the long-seed KDP crystal has good crystalline quality. In the wavelength range of 377–1022 nm, the transmittance of the long-seed KDP crystal is higher than 90%. The fluence for the 50% probability of laser-induced damage (LID) is $18.5~\text{J}/\text{cm}^{2}$ (3 ns, 355 nm). Several test points survive when the laser fluence exceeds $30~\text{J}/\text{cm}^{2}$ (3 ns, 355 nm), indicating the good LID performance of the long-seed KDP crystal. At present, the growth of a long-seed DKDP crystal is under way.

Strain-Induced Structural Evolution and High Robustness in Single Crystalline Fivefold Twinned Cu@C Coaxial Nanowires

Here, we developed single crystalline Cu@C nanowires with fivefold twinned structure via a facile hydrothermal method. In situ uniaxial tension tests of these NWs performed in transmission electron microscopy chamber reveal the ultrahigh strength (as much as 6.2 GPa) accompanied by favorable ductility (elongation>15%). The excellent performances benefit from nanoscale dimensions, unique penta-twinned geometry and good crystalline quality with protection of carbon shells. The study also provides direct experimental evidence for the theoretical modeling on the deformation mechanisms of metallic nanowires that have appeared in recent years. We expect that these findings can open a new window for applications in micro-or nanoelectromechanical devices where superior mechanical performances are desirable.

XRD Studies of Synthesized Bi2S3Crystalline Materials

Bismuth sulfide preparation and its x-ray diffraction studies are reported in this paper. The author have synthesized Bi2Sx (x = 3.15, 3.45) compound material with different sulfur content by conventional high temperature solid state solvothermal reaction of bismuth and sulfur which conforms that the (121) preferred orientation with crystallite size ~30 nm and splitting of peaks due to orthorhombic structure matches well with the standard data and demonstrate good crystalline quality and structural homogeneity of synthesized powder.This paper also describes the synthesis and x-ray diffraction studies of bismuth sulfide powder via versatile precipitation technique . Bismuth sulfide powder was synthesized using thiourea and sodium dodecyl sulfate or in absence of any surfactant maintained at 800C for 12 h keeping pH of solution constant at 1.4. Synthesized powder was characterized by x-ray diffraction technique which indicates that surfactants play major role in synthesis of bismuth sulfide that conforms the crystallite size ~35 nm. The employed solid state solvothermal technique played an important role to progress the homogeneous reaction and preparation of pure and fine bismuth sulfide powder. The possible application of this material in photovoltaic devices is suggested.

The Microwave-Assisted Synthesis and Gas Sensing Properties for Ethanol of SnO2 Nanomaterials

With the advantages of the microwave-assisted method, good crystalline quality SnO2nanomaterials were successfully synthesized. The morphology and microstructure of SnO2were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and high-resolution (HRTEM) used to examine SnO2nanomaterials. Indirect-heating sensors based on nanorods were fabricated and investigated for the gas sensing properties to ethanol. The investigation demonstrates that the sensor based on prepared SnO2nanomaterials has good sensitivity, low detection limit and short response and reversion time to ethanol at 275 °C.

DEPTH-DEPENDENT TETRAGONAL DISTORTION STUDY OF AlGaN EPILAYER THIN FILM USING RBS AND CHANNELING TECHNIQUE

An epilayer of wide-band gap Al x Ga 1-x N was grown on sapphire by metal organic chemical vapor deposition (MOCVD) method with a GaN buffer layer of thickness slightly greater than 1 μm. Average composition of Al in the AlGaN layer is determined by Rutherford backscattering spectroscopy (RBS). Simulation of the random spectra reveals that the AlGaN layer has a composition of Al 0.05 Ga 0.95 N and a thickness of 200 nm. Low ratio of channeling and random spectra yields suggests good crystalline quality of ternary AlGaN epilayer. Tetragonal distortion (eT) caused by elastic strain in AlGaN is measured from channeling angular scans taken around an off-normal [Formula: see text] axis in the [Formula: see text] plane of the AlGaN layer. The resulting AlGaN is identified to be showing compressive strain at the interfacial layer and the magnitude of the stress reduces towards the near-surface layer. It can be expected from the results that a 550 nm thick, epitaxially grown, AlGaN layer on sapphire can be relaxed completely (eT = 0).

Effect of Propane on Low Temperature Growth of 3C-SiC Film on Si (111) by Plasma Assisted CVD

To demonstrate the formation of 3C-SiC film on Si (111) at low substrate temperature, the effects of C3H8 on the crystalline quality of the 3C-SiC films on Si (111) have been investigated by changing the flow rate of C3H8 at the substrate temperature of 950 °C. The crystalline quality has been investigated by transmission electron microscope and X-ray diffraction. 3C-SiC is epitaxially grown on Si(111) and the 3C-SiC films are in either near single crystalline or highly oriented form with stacking faults and twin. It is expected that the film with good crystalline quality may grow at around 2.5 in the ratio of the flow rate of C3H8 to SiH4 and any microstructures of 3C-SiC films on Si (111) can be controlled by accurately controlling the ratio of C/Si.

Quality Investigation of 3C-SiC Crystals Grown by CF-PVT Technique

This work presents the crystalline quality investigation of 3C-SiC unseeded crystals grown from vapor phase. Samples were polished after different crystallographic planes from crystals grown with or without nitrogen flow. The structural and optical investigation showed that the central part of the samples exhibited a very good crystalline quality. The best samples proved to be the {100} growth sectors where the only defects found were stacking faults with a defect density under 103 cm-1. At the edges, i.e. between two adjacent growth sectors, structural investigation by transmission electron microscopy revealed stacking faults and hexagonal polytype inclusions. The nitrogen doping was found not to have an influence on the crystalline quality.

The Crystal Structural Properties of Sputtered ZnO Films Containing Internal Stress

The ZnO films were deposited on Si substrate by radio frequency (RF) magnetron sputtering. The effects of the Ar/O2 ratios on the structural characteristics and the internal stress in the ZnO films have been studied. The SEM images shows that the ZnO grains are nano-sized and tightly packed. The ZnO films are highly c-axis oriented with the (002) plane parallel to the substrate. The samples has a stress of the order of 1.0 × 1010 dyn/cm2. It is found that the size of ZnO crystal grains distinctly depends on the stress in the ZnO films. In order to deposite ZnO films with good crystalline quality, the stress caused by the growth process can be depressed by adjusting the Ar/O2 ratios.

P-type CuInSe2 thin films prepared by selenization of one-step electrodeposited precursors

In this study, p-type CuInSe2 (CIS) films were prepared by selenization of one-step electrodeposited Cu-In-2Se (atomic ratio) precursors. To obtain high-quality, dense, and homogeneous CIS films for solar cell application, the effects of substrate temperatures during selenization and precursor compositions on the final microstructures were systematically investigated. The precursor layers evolved in very different ways under different selenization conditions. The final microstructures and phases of the films depended critically on the precursor compositions, selenization temperature, and the selenization thermal process history. Low melting temperature CuxSe phase, which tended to segregate at the film surface, can efficiently assist the CIS grain growth. Large hexagonal CuSe platelets were formed at a temperature as low as 170 °C in Cu-rich precursor, which acted as an element-transport flux agent at higher temperature under high Se vapor and reacted with In-Se selenide to form CIS at temperatures above 500 °C. Good crystalline quality chalcopyrite CIS film was obtained at a selenization temperature of 550 °C.