Selective Area Growth and Characterization of GaN Nanorods Fabricated by Adjusting the Hydrogen Flow Rate and Growth Temperature with Metal Organic Chemical Vapor Deposition

CaN nanorods are successfully fabricated by adjusting the flow rate ratio of hydrogen （H2）/nitrogen （N2） and growth temperature of the selective area growth （SAG） method with metal organic chemical vapor deposition （MOCVD）. The SAG template is obtained by nanospherical-lens photolithography. It is found that increasing the flow rate of 1-12 will change the CaN crystal shape from pyramid to vertical rod, while increasing the growth temperature will reduce the diameters of GaN rods to nanometer scale. Finally the CaN nanorods with smooth lateral surface and relatively good quality are obtained under the condition that the H2：N2 ratio is 1：1 and the growth temperature is 1030℃. The good crystal quality and orientation of GaN nanorods are confirmed by high resolution transmission electron microscopy. The cathodoluminescence spectrum suggests that the crystal and optical quality is also improved with increasing the temperature.

Effect of nitrogen gas flow and growth temperature on extension of GaN layer on Si

The effect of nitrogen flow and growth temperature on extension of GaN on Si substrate has been studied.By increasing the nitrogen flow whose outlet is located in the center of the MOCVD(metal–organic chemical vapor deposition)gas/particle screening flange and by increasing the growth temperature of HT-AlN and AlGaN buffer layers near the primary flat of the wafer,the GaN layer has extended more adequately on Si substrate.In the meantime,the surface morphology has been greatly improved.Both the AlN and GaN crystal quality uniformity has been improved.X-ray diffraction results showed that the GaN(0002)XRD FWHMs(full width at half maximum)decreased from 579 arcsec~1655 arcsec to around 420 arcsec.

The Research on Growth Temperature of Ge/Si Thin Films Grown by Magnetron Sputtering

The films of Ge and Si were grown on the substrate Si (100) by magnetron sputtering at 2.5 Pa Ar pressure.The growth temperature of films was 100℃,250℃,400℃and 550℃.The structure and composition were analysised by Raman scattering.The poly-crystal peak and crystal peak of Ge were observed in these films.The results indicate that the single crystal film of Ge was prepared at the substrate temperature of 400℃.The peak of acoustic phonons of Ge was 98 cm^(-1) and that of Si was 170 cm^(-1).

The Efficiency Droop of InGaN-Based Green LEDs with Different Superlattice Growth Temperatures on Si Substrates via Temperature-Dependent Electroluminescence

InGaN-based green light-emitting diodes （LEDs） with different growth temperatures of superlattice grown on Si （111） substrates are investigated by temperature-dependent electroluminescence between 100 K and 350K. It is observed that with the decrease of the growth temperature of the superlattice from 895℃ to 855℃, the forward voltage decreases, especially at low temperature. We presume that this is due to the existence of the larger average size of V-shaped pits, which is determined by secondary ion mass spectrometer measurements. Meanwhile, the sample with higher growth temperature of superlattice shows a severer efficiency droop at cryogenic temperatures （about 100 K-150 K）. Electron overflow into p-GaN is considered to be the cause of such phenomena, which is relevant to the poorer hole injection into multiple quantum wells and the more reduced effective active volume in the active region.

Effects of Growth Temperature on Structural and Electrical Properties of Li-N-H Codoped ZnO

Effects of growth temperature on the structural and electrical properties of Li-N-H codoped ZnO thin films grown by DC reactive magnetron sputtering were investigated. Scanning electron microscopy and X-ray diffraction results showed that increasing growth temperature could improve the crystalline quality. But Hall measurement results showed that growth temperature had a nonlinear influence on the electrical property. The variation of electrical properties with the growth temperature was found to be related to the activated concentration of N in ZnO and the evaporation of Li during the growth process, derived from the Hall measurement and the second ion mass spectroscopy measurement.

Influence of growth temperature and thickness on the orientation of Cu(In,Ga)Se_2 film

Cu(In,Ga)Se2(CIGS) films are deposited on the Na-free glass substrate using three-stage co-evaporation process,and the effects of thickness and growth temperature on the orientation of CIGS film are investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM).When the growth of CIGS film does not experience the Cu-rich process,the increase of the growth temperature at the second stage(Ts2) promotes the(112) orientation of CIGS film,and weakens the(220) orientation.Nevertheless,when the growth of CIGS film experiences Cu-rich process,the increase of Ts2 significantly promotes the(220) orientation.In addition,with the thickness of CIGS film decreasing,the extent of(In,Ga)2Se3(IGS) precursor orientation does not change except for the intensity of Bragg peak,yet the(220) orientation of following CIGS film is hindered,which suggests that(112) plane preferentially grows at the initial growth of CIGS film.

Fractal Nature of Crack Growth under Different Temperature

We have studied numerically a simple crack growth model in a two-dimensional triangular lattice of bonds and nodes which incorporates the surface of a growing crack bond-breaking probability P-i similar to exp{(-V-i+E(i))phi(T)}, where E(i) is elastic energy stored in the i-th bond. Different energy temperature factors phi(T) are employed during crack formation and propagation process with a uniform dilation strain case and a shear case and with periodic boundary condition in the horizontal direction. Our results show that the patterns of the cracks generated are fractal structure and the effective fractal dimensionalities decrease with the increase of the temperature factor phi(T)(the absolute temperature T decreasing). In the paper we also discuss the relation between the effective fractal dimension D-eff (the radius R(g) of gyration) and the fractal dimensions D (the radius R of circular), and also give their modification values Omega about two kinds of methods in the lattice model.

Centimeter-sized Cs_(3)Cu_(2)I_(5)single crystals grown by oleic acid assisted inverse temperature crystallization strategy and their films for high-quality X-ray imaging

Low-dimensional halide perovskites have become the most promising candidates for X-ray imaging,yet the issues of the poor chemical stability of hybrid halide perovskite,the high poisonousness of lead halides and the relatively low detectivity of the lead-free halide perovskites which seriously restrain its commercialization.Here,we developed a solution inverse temperature crystal growth(ITCG)method to bring-up high quality Cs_(3)Cu_(2)I_(5)crystals with large size of centimeter order,in which the oleic acid(OA)is introduced as an antioxidative ligand to inhibit the oxidation of cuprous ions effieiently,as well as to decelerate the crystallization rate remarkalby.Based on these fine crystals,the vapor deposition technique is empolyed to prepare high quality Cs_(3)Cu_(2)I_(5)films for efficient X-ray imaging.Smooth surface morphology,high light yields and short decay time endow the Cs_(3)Cu_(2)I_(5)films with strong radioluminescence,high resolution(12 lp/mm),low detection limits(53 nGyair/s)and desirable stability.Subsequently,the Cs_(3)Cu_(2)I_(5)films have been applied to the practical radiography which exhibit superior X-ray imaging performance.Our work provides a paradigm to fabricate nonpoisonous and chemically stable inorganic halide perovskite for X-ray imaging.

EFFECT OF SUBSTRATE TEMPERATURE ON Y-Ba-Cu-O THIN FILMS IN SITU GROWTH BY MOCVD

Superconducting thin films of YBa2Cu3O7-x（Y-Ba-Cu-O） with Tc more than 85K have been deposited in situ by metalorganic chemical vapor deposition （MOCVD） on yttria stabilized zirconia（YSZ） substrates. The relationship of film orientation on substrate temperature and the lowest formation temperature region of superconducting phase have been obtained after changing the substrate temperature. The epitaxial relation between Y-Ba-Cu-O films and the YSZ su bstrates were discussed.

Growth and Optical Properties of ZnO Films and Quantum Wells

The growth characteristics during metalorganic chemical vapor deposition and optical properties of ZnO films on sapphire （Al2O3） （0001） and （1120） substrates are studied. For the former,the effects of two important growth parameters,i, e. temperature and pressure, are investigated in detail. Due to the large lattice mismatch between the film and the substrate, ZnO nanocrystals are usually obtained. The growth behavior at the film-substrate interface is found to be strongly dependent on the growth temperature,while the growth pressure determines the shape of the nanostructures as they grow. It is difficult to obtain ZnO films that have good quality and a smooth surface simultaneously. Due to the smaller lattice mismatch,the critical thickness of ZnO on the Al2O3 （1120） surface is found to be much larger than that on the Al2O3 （0001） surface. ZnO/MgZnO quantum wells with graded well thicknesses are grown on the Al2O3 （1120） surfaces,and their optical properties are studied. The built-in electric field in the well layer, generated by the piezoelectric effect, is estimated to be 3 × 10^5 V/cm. It is found that growth at low temperatures and low pressures may facilitate the incorporation of acceptor impurities in ZnO.

Zn/O ratio and oxygen chemical state ofnanocrystalline ZnO films grown atdifferent temperatures

ZnO nanocrystalline films are prepared on Si substrates at different temperatures by using metal-organic chemical vapour deposition （MOCVD）. It is observed that when the growth temperature is low, the stoichiometric ratio between Zn and 0 atoms has a large deviation from the ideal ratio of 1：1. The ZnO grains in the film have small sizes and are not well crystallized, resulting in a poor photoluminescence （PL） property. When the temperature is increased to an appropriate value, the Zn/O ratio becomes optimized, and most of Zn and 0 atoms are combined into Zn-O bonds. Then the film has good crystal quality and good PL property. If the temperature is fairly high, the interracial mutual diffusion of atoms between the substrate and the epitaxial film appears, and the desorption process of the oxygen atoms is enhanced. However, it has no effect on the film property. The film still has the best crystal quality and PL property.

Effect of Deposition Time on Microstructures and Growth Behavior of ZrC Coatings Prepared by Low Pressure Chemical Vapor Deposition with the Br2-Zr-C3H6-H2-Ar System

ZrC coatings were deposited on graphite substrates by low pressure chemical vapor deposition（LPCVD） with the Br2-Zr-C3H6-H2-Ar system. The effects of deposition time on the microstructures and growth behavior of ZrC coatings were investigated. ZrC coating grew in an island-layer mode. The formation of coating was dominated by the nucleation of ZrC in the initial 20 minutes, and the rapid nucleation generated a fine-grained structure of ZrC coating. When the deposition time was over 30 min, the growth of coating was dominated by that of crystals, giving a column-arranged structure. Energy dispersive X-ray spectroscopy showed that the molar ratio of carbon to zirconium was near 1：1 in ZrC coating, and X-ray photoelectron spectroscopy showed that ZrC was the main phase in coatings, accompanied by about 2.5mol% ZrO2 minor phase.

Optimization of Technical Parameters for Detecting Mycobacteria in Hospital Wastewater in Tropical Urban Areas: The Case of the City of Abidjan (Côte d’Ivoire)

The loads of organic matter, microorganisms, detergents and antibiotics in liquid hospital effluents make them complex environments, raising numerous health and ecological questions. Investigations of mycobacteria in water lack adequate techniques. This study is the first part of a pilot project aimed at developing an optimized protocol for the isolation of mycobacteria from hospital effluents, as a prelude to more in-depth investigation in this matrix. The aim was to compare the performance of two decontamination methods, three culture media and two incubation temperatures generally proposed in the literature, in order to identify the most effective methods in each case, as well as possible areas for improvement in the isolation of these germs from this environmental matrix. The results show that liquid hospital effluent can be decontaminated using both the NaOH method (4%;for 30 min.) and the CPC method (0.05%;for 30 min.), with the same mycobacteria recovery efficiency. Despite the low concentration, decontamination with CPC killed more mycobacteria and sufficiently eliminated contaminating germs. In contrast, decontamination with NaOH was less harmful to mycobacteria, but did not remove many contaminating germs. On the other hand, LJG medium performed better than LJGF medium and LJGP medium for the growth of mycobacteria in hospital waters. Finally, there was no difference in performance between the two incubation temperatures of 30℃ and 37℃. The results of this study show that further evaluation of existing protocols is required in order to optimize methods for the pre-treatment of hospital effluent for the isolation of mycobacteria.

Revisiting the Seasonal Evolution of the Indian Ocean Dipole from the Perspective of Process-Based Decomposition

The seasonal phase-locking feature of the Indian Ocean Dipole(IOD)is well documented.However,the seasonality ten-dency of sea surface temperature anomalies(SSTAs)during the development of the IOD has not been widely investigated.The SSTA tendencies over the two centers of the IOD peak in September-October-November are of different monthly amplitudes.The SSTA tendency over the west pole is small before June-July-August but dramatically increases in July-August-September.Meanwhile,the SSTA tendency over the east pole gradually increases before June-July-August and decreases since then.The growth rate attribution of the SSTAs is achieved by examining the roles of radiative and non-radiative air-sea coupled thermodynamic processes through the climate feedback-response analysis method(CFRAM).The CFRAM results indicate that oceanic dynamic processes largely contribute to the total SSTA tendency for initiating and fueling the IOD SSTAs,similar to previous studies.However,these results cannot ex-plain the monthly amplitudes of SSTA tendency.Four negative feedback processes(cloud radiative feedback,atmospheric dynamic processes,surface sensible,and latent heat flux)together play a damping role opposite to the SSTA tendency.Nevertheless,the sea surface temperature-water vapor feedback shows positive feedback.Specifically,variations in SSTAs can change water vapor con-centrations through evaporation,resulting in anomalous longwave radiation that amplifies the initial SSTAs through positive feedback.The effect of water vapor feedback is well in-phase with the monthly amplitudes of SSTA tendency,suggesting that the water vapor feedback might modulate the seasonally dependent SSTA tendency during the development of the IOD.

Growth-temperature-dependent optical and acetone detection properties of ZnO thin films

Zinc oxide （ZnO） thin films were prepared onto glass substrates at moderately low growth tempera- ture by two-stage spray pyrolysis technique. The effects of growth temperature on structural, optical and acetone detection properties were investigated with X-ray diffractometry, a UV-visible spectrophotometer, photoluminescence （PL） spectroscopy and a homemade gas sensor testing unit, respectively. All the films are polycrystalline with a hexagonal wurtzite phase and exhibit a preferential orientation along [002] direction. The film crystallinity is gradually enhanced with an increase in growth temperature. The optical measurements show that all the films are physically highly transparent with a transmittance greater than 82% in the visible range. The band gap of the film is observed to exhibit a slight red shift with an increasing growth temperature. The PL studies on the films show UV/violet PL band at - 395 nm. Among all the films investigated, the film deposited at 250℃ demonstrates a maximum sensitivity of 13% towards 20 ppm of acetone vapors at 300℃ operating temperature.

Combined effects of carrier scattering and Coulomb screening on photoluminescence in InGaN/GaN quantum well structure with high In content

Photoluminescence(PL) spectra of two different green InGaN/GaN multiple quantum well(MQW) samples S1 and S2,respectively with a higher growth temperature and a lower growth temperature of InGaN well layers are analyzed over a wide temperature range of 6 K-3 30 K and an excitation power range of 0.001 mW-75 mW.The excitation power-dependent PL peak energy and linewidth at 6 K show that in an initial excitation power range,the emission process of the MQW is dominated simultaneously by the combined effects of the carrier scattering and Coulomb screening for both the samples,and both the carrier scattering effect and the Coulomb screening effect are stronger for S2 than those for S1;in the highest excitation power range,the emission process of the MQWs is dominated by the filling effect of the high-energy localized states for S1,and by the Coulomb screening effect for S2.The behaviors can be attributed to the fact that sample S2 should have a higher amount of In content in the InGaN well layers than S1 because of the lower growth temperature,and this results in a stronger component fluctuation-induced potential fluctuation and a stronger well/barrier lattice mismatchinduced quantum-confined Stark effect.This explanation is also supported by other relevant measurements of the samples,such as temperature-dependent peak energy and excitation-power-dependent internal quantum efficiency.

Combining QTL mapping and expression profile analysis to identify candidate genes of cold tolerance from Dongxiang common wild rice(Oryza rufipogon Griff.)

Rice（Oryza sativa L.）, a tropical and subtropical crop, is susceptible to low temperature stress during seedling, booting, and flowering stages, which leads to lower grain quality levels and decreasing rice yields. Cold tolerance is affected by multiple genetic factors in rice, and the complex genetic mechanisms associated with chilling stress tolerance remain unclear. Here, we detected seven quantitative trait loci（QTLs） for cold tolerance at booting stage and identified one cold tolerant line, SIL157, in an introgression line population derived from a cross between the indica variety Guichao 2, as the recipient, and Dongxiang common wild rice, as the donor. When compared with Guichao 2, SIL157 showed a stronger cold tolerance during different growth stages. Through an integrated strategy that combined QTL-mapping with expression profile analysis, six candidate genes, which were up-regulated under chilling stress at the seedling and booting developmental stages, were studied. The results may help in understanding cold tolerance mechanisms and in using beneficial alleles from wild rice to improve the cold tolerance of rice cultivars through molecular marker-assisted selection.

Effect of hydrogen on low temperature epitaxial growth of polycrystalline silicon by hot wire chemical vapor deposition

Polycrystalline silicon （poly-Si） films were prepared by hot-wire chemical vapor deposition （HWCVD） at a low substrate temperature of 525 ℃. The influence of hydrogen on the epitaxial growth of ploy-Si films was investigated. Raman spectra show that the poly-Si films are fully crystallized at 525 ℃ with a different hydrogen dilution ratio （50%-91.7%）. X-ray diffraction, grazing incidence X-ray diffraction and SEM images show that the poly-Si thin films present （100） preferred orientation on （100） c-Si substrate in the high hydrogen dilution condition. The P-type poly-Si film prepared with a hydrogen dilution ratio of 91.7% shows a hall mobility of 8.78 cm2/（V-s） with a carrier concentration of 1.3 × 10^20 cm^-3, which indicates that the epitaxial poly-Si film prepared by HWCVD has the possibility to be used in photovoltaic and TFT devices.

Effect of six kinds of scale inhibitors on calcium carbonate precipitation in high salinity wastewater at high temperatures

Precipitation of calcium carbonate （CaCOs） scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one （scale inhibitor SQ-1211） to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca^2＋ was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80℃ at pH 8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCOs changed from calcite to aragonite.

High-strain InGaAs/GaAs quantum well grown by MOCVD

High-strain InGaAs/GaAs quantum wells （QWs） are grown by low-pressure metal-organic chemical vapor deposition （LP-MOCVD）. Photoluminescence （PL） at room temperature is applied for evaluation of the optical property. The influence of growth temperature, V/III ratio, and growth rate on PL characteristic are investigated. It is found that the growth temperature and V/III ratio have strong effects on the peak wavelength and PL intensity. The full-width at half-maximum （FWHM） of PL peak increases with higher growth rate of InGaAs layer. The FWHM of the PL peak located at 1039 nm is 20.1 meV, which grows at 600 ℃ with V/ III ratio of 42.7 and growth rate of 0.96 μm/h.