提高(100)晶向磷化铟单晶的成晶率和质量的研究

通过对高压液封直拉法单晶生长过程的热传输和影响熔体温度起伏的几个关键因素的分析,研究适合生长(100)晶向磷化铟单晶的热场系统,有效地降低了孪晶产生的几率,重复地生长出了整锭掺硫和掺铁的、直径为50mm和76mm的(100)磷化铟单晶.测试结果表明我们生长(100)磷化铟单晶的热场在生长过程中使晶锭保持较为平坦的固液界面,可稳定地获得具有低的缺陷密度和良好的电学均匀性的高质量磷化铟单晶材料.     

A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of GaN_xAs_yP_(1-x-y)/GaP quantum wells on GaP substrates

The GaP-based dilute nitride direct band gap material Ga（NAsP） is gaining importance due to the monolithic integra- tion of laser diodes on Si microprocessors. The major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga（NAsP）/GaP QW lasers. Therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen （N） concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs with that of the GaNxAsyP1-x-y/Al2Ga1-2P QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of N into the well and AI into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.     

磷化钨催化转化纤维素制乙二醇

 首次将磷化钨 (WP) 催化剂应用于纤维素的催化转化反应. 结果表明, 与碳化钨催化剂类似, WP 催化剂也可高效地实现纤维素转化. 在 H2 初始压力为 6 MPa, 反应温度为 245 oC 时, 20%WP/AC (活性炭) 催化纤维素高选择性地生成乙二醇, 其收率为 25.4 mol%. 2% 镍的加入使得该催化剂上乙二醇收率增至 46.0 mol%, 表明 Ni 与 WP 之间存在着明显的协同作用.     

Terminal, anionic carbide, nitride, and phosphide transition-metal complexes as synthetic entries to low-coordinate phosphorus derivatives

Anionic terminal one-atom nitride, phosphide, and carbide complexes are excellent starting materials for the synthesis of ligands containing low-coordinate phosphorus centers in the protecting coordination sphere of the metal complex. Salt-elimination reactions with chlorophosphanes lead to phosphaisocyanide, iminophosphinimide, and diorganophosphanylphosphinidene complexes in which the unusual phosphorus ligands are stabilized by coordination. X-ray structure analyses and density-functional calculations illuminate the bonding in these compounds.     

Cross-sectional scanning tunneling microscopy and spectroscopy of strain in buried heterostructure lasers

Cross-sectional scanning tunneling microscopy and spectroscopy have been used to probe the unreconstructed (1 1 0) surface of a commercially available buried heterostructure laser in ultra high vacuum. Complex re-growth above the non-linear blocking layers is shown to induce tensile strain in the device. Spectroscopic measurements show an increase in both the density of filled valence band states and empty conduction band states as a result of the strain, with a particularly large increase at −3.1 V. Current imaging tunneling spectroscopy measurements show an increase in the tunneling current in to and out of the strained regions at both gap voltage polarities, consistent with the spectroscopy. Moving towards tensile strain, InP is known to maintain much the same bandgap, with the split-off level and lower lying states being drawn up towards the valence band edge, consistent with the data.     

Investigation of morphology evolution of the In‐rich inclusions and the corresponding defects in InP single crystals

Submicron, micron and millimeter‐scale In‐rich inclusions with different polyhedral morphologies are observed, which are directionally embedded in the InP matrix along <011> direction. The arrangement direction and morphological change of the In‐rich inclusions at different scales are investigated to reveal their morphology evolution. The relative size of the facets ({100} and {111}_P/In) bounding the polyhedral In‐rich inclusions is different from the reported results in other crystals, especially when the size of In‐rich inclusions is up to millimeter‐scale. The growth rate dispersion effect and the initial morphologies of the In‐rich droplets have an obvious effect on the final shape of the In‐rich inclusions. Dislocation enrichment surrounding the In‐rich inclusion is observed, which is contributed to the volume expansion of liquid‐solid phase transition and the difference of the thermal expansion coefficient and thermal conductivity between In‐rich droplet and InP matrix. The size and shape of the dislocation enriched region are closely related to the size and shape of the originating In‐rich droplet and the growth condition.     

Preparation of Hierarchical Cube‐on‐plate Metal Phosphides as Bifunctional Electrocatalysts for Overall Water Splitting

To rationally design efficient and cost‐effective electrocatalysts, a simple but efficient strategy has been developed to directly anchor prussian blue analogue (PBA) nanocubes on cobalt hydroxide nanoplates (PBA@Co(OH)₂) via the in‐situ interfacial precipitation process. Subsequently, the thermal treatment in the presence of sodium hydrogen phosphite enabled the successful transition into metal phosphides with the hierarchical cube‐on‐plate structure. When used as electrocatalytsts, the obtained bimetal phosphides exhibited good bifunctional electrocatalytic activities for hydrogen and oxygen evolution reactions with good long‐term stability. Thus, an enhanced performance for overall water splitting can be achieved, which could be ascribed to the hierarchical structure and favorable composition of as‐prepared bimetal phosphide for rapid electron and mass transfer. The present study demonstrates a favorable approach to modulate the composition and structure of metal phosphide for enhancing the electrocatalytic ability toward water splitting.     

Deep defect levels in diode structures based on gallium phosphide

We have studied the characteristic features of defect formation and generation of deep levels that control degradation processes in GaP diodes. We have shown that degradation of GaP diodes is mainly connected with the presence of defects in the space charge region of the p-n junction which are V_Ga-donor complexes, antistructural P_Ga defects, and also intrinsic V_P structural defects with high density of localized states. We have established an interconnection between the degradation rate and the features of the energy spectrum of deep levels in GaP diodes, allowing us to use analysis of tunneling spectra for diagnostics of p-n junction quality and prediction of GaP diode degradation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 78–81, January–February, 2006.     

Effect of gas flow ratio on the microstructure and mechanical properties of boron phosphide films prepared by reactive magnetron sputtering

Boron phosphide films were grown on silicon substrate by radio frequency reactive magnetron sputtering using boron target and hydrogen phosphine at different gas flow ratios (PH₃/Ar) at lower temperature. The chemical composition, microstructure and mechanical properties were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectrum, FTIR spectrum, surface profilometer and nano-indenter. The results indicate that the atomic ratio (P/B) rises from 1.06 up to 1.52 with the gas flow ratio increasing from 3/50 to 15/50. Simultaneously, the hardness and Young's modulus decrease from 25.4 GPa to 22.5 GPa, and 250.4 GPa to 238.4 GPa, respectively. Microstructure transforms from microcrystalline state to amorphous state along with the gas flow ratio increasing. Furthermore higher gas flow ratio leads to lower stress. The BP film prepared at the gas flow ratio of 3/50 can be contributed with the best properties.     

A computational study of silicon-doped aluminum phosphide nanotubes

We performed density functional theory (DFT) calculations to investigate the properties of silicon-doped (Si-doped) models of representative (4,4) armchair and (6,0) zigzag aluminum phosphide nanotubes (AlPNTs). The structures were allowed to relax and the chemical shielding (CS) parameters were calculated for the atoms of optimized structures. The results indicated that the band gap energies and dipole moments detect the effects of dopant. The CS parameters also indicated that the Al and P atoms close to the Si-doped region are such reactive atoms, which make the Si-doped AlPNTs more reactive than the pristine AlPNTs. Moreover, replacement of P atom by the Si atom makes AlPNT more reactive than the replacement of Al atom by the Si atom.