High Lattice Match Growth of InAsSb Based Materials by Molecular Beam Epitaxy

High lattice match growth of InAsSb based materials on GaSb substrates is demonstrated. The present results indicate that a stable substrate temperature and the optimal flux ratios are of critical importance in achieving a homogeneous InAsSb based material composition throughout the growth period. The quality of these epilayers is assessed using a high-resolution x-ray diffraction and atomic force microscope. The mismatch between the GaSb substrate and InAsSb alloy achieves almost zero, and the rms surface roughness of InAsSb alloy achieves around 1.7A over an area of 28μm × 28μm. At the same time, the mismatches between GaSb and InAs/InAs0.73Sb0.27 superlattices （SLs） achieve approximately 100 arcsec （75 periods） and zero （300 periods）, with the surface rms roughnesses of InAs/InAs0.73Sb0.27 SLs around 1.8 A （75 periods） and 2.1A （300 periods） over an area of 20 μm×20 μm, respectively. After fabrication and characterization of the devices, the dynamic resistance of the n-barrier-n InAsSb photodetector near zero bias is of the order of 10^6Ω·cm^2. At 77K, the positive-intrinsic-negative photodetectors are demonstrated in InAsSb and InAs/InAsSb SL （75 periods） materials, exhibiting fifty-percent cutoff wavelengths of 3.8μm and 5.1μm, respectively.

Room-Temperature Annealing of 1 MeV Electron Irradiated Lattice Matched In0.53Ga0.47As/InP Multiple Quantum Wells

Long-term room-temperature annealing effects of InGaAs/InP quantum wells with different wells （namely triple wells and five wells embedded） and bulk InCaAs are investigated after high energy electron irradiation. It is observed that the photoluminescence （PL） intensity of bulk InGaAs materials is enhanced after low dose electron irradiation and the PL intensity for all the three samples is degraded dramatically when the electron dose is relatively high. With respect to the room-temperature annealing, we find that the PL intensity for both samples recovers relatively fast at the initial stage. The PL performance of multiple quantum-well samples shows better recovery after irradiation compared with the results of bulk InGaAs materials. Meanwhile, the recovery speed factors of multiple quantum-well samples are relatively faster than those of the bulk InGaAs materials as well. We infer that the recovery difference between the quantum-well materials and bulk materials originates from the fact that the radiation induced defects are confined in the quantum wells as a consequence of the free energy barrier between the In0.53Ga0.47 As wells and InP barrier layers.

Different roles of surfaces’ interaction on lattice mismatched/matched surfaces in facilitating ice nucleation

The freezing of water is one of the most common processes in nature and affects many aspects of human activity. Ice nucleation is a crucial part of the freezing process and usually occurs on material surfaces. There is still a lack of clear physical pictures about the central question how various features of material surfaces affect their capability in facilitating ice nucleation. Via molecular dynamics simulations, here we show that the detailed features of surfaces, such as atomic arrangements, lattice parameters, hydrophobicity, and function forms of surfaces’ interaction to water molecules, generally affect the ice nucleation through the average adsorption energy per unit-area surfaces to individual water molecules, when the lattice of surfaces mismatches that of ice. However, for the surfaces whose lattice matches ice, even the detailed function form of the surfaces’ interaction to water molecules can largely regulate the icing ability of these surfaces. This study provides new insights into understanding the diverse relationship between various microscopic features of different material surfaces and their nucleation efficacy.

Steering spatially separated dual sites on nano-TiO_(2)through SMSI and lattice matching for robust photocatalytic hydrogen evolution

Spatial isolation of different functional sites at the nanoscale in multifunctional catalysts for steering reaction sequence and paths remains a major challenge.Herein,we reported the spatial separation of dual-site Au and RuO_(2)on the nanosurface of TiO_(2)(Au/TiO_(2)/RuO_(2))through the strong metal-support interaction(SMSI)and the lattice matching(LM)for robust photocatalytic hydrogen evolution.The SMSI between Au and TiO_(2)induced the encapsulation of Au nanoparticles by an impermeable TiO_(x)overlayer,which can function as a physical separation barrier to the permeation of the second precursor.The LM between RuO_(2)and rutile-TiO_(2)can increase the stability of RuO_(2)/TiO_(2)interface and thus prevent the aggregation of dual-site Au and RuO_(2)in the calcination process of removing TiO_(x)overlayer of Au.The photocatalytic hydrogen production is used as a model reaction to evaluate the performance of spatially separated dual-site Au/TiO_(2)/RuO_(2)catalysts.The rate of hydrogen production of the Au/TiO_(2)/RuO_(2)is as high as 84μmol h^(−1)g^(−1)under solar light irradiation without sacrificial agents,which is 2.5 times higher than the reference Au/TiO_(2)and non-separated Au/RuO_(2)/TiO_(2)samples.Systematic characterizations verify that the spatially separated dual-site Au and RuO_(2)on the nanosurface of TiO_(2)can effectively separate the photo-generated carriers and lower the height of the Schottky barrier,respectively,under UV and visible light irradiation.This study provides new inspiration for the precise construction of different sites in multifunctional catalysts.

Li_(2)TiO_(3) Dopant and Phosphate Coating Improve the Electrochemical Performance of LiCoO2 at 3.0-4.6 V

A sol-gel tandem with a solid-phase modification procedure was developed to synthesize Li_(2)TiO_(3)-doped LiCoO_(2) together with phosphate coatings(denoted as LCO-Ti/P),which possesses excellent high-voltage performance in the range of 3.0-4.6 V.The characterizations of X-ray diffraction,high-resolution transmission electron microscopy,and X-ray photoelectron spectroscopy illustrated that the modified sample LCO-Ti/P had the dopant of monoclinic Li_(2)TiO_(3) and amorphous Li3PO4 coating layers.LCO-Ti/P has an initial discharge capacity of 211.6 mAh/g at 0.1 C and a retention of 85.7%after 100 cycles at 1 C and 25±1°C between 3.0 and 4.6 V.Nyquist plots reflect that the charge transfer resistance of LCO-Ti/P after 100 cycles at 1 C is much lower than that of the spent LCO,which benefits Li-ion diffusion.Density functional theory calculations disclose the superior lattice-matching property of major crystal planes for Li_(2)TiO_(3) and LiCoO_(2),the lower energy barriers for Li-ion diffusion in Li_(2)TiO_(3),and the suppressed oxygen release performance resulting from phosphate adsorption.This work provides useful guidance on the rational design of the high-voltage performance of modified LiCoO_(2) materials in terms of lattice-matching properties aside from the phosphate coating to reduce the energy barriers of Li-ion diffusion and enhance cycling stability.

Discrepancy of the magnetic behaviors and crystalline structure on the Co/FeMn and FeMn/Co interfaces with ultrathin Pt spacer

The exchange coupling at the ferromagnetic/antiferromagnetic （FM/AFM） interface is influenced by both the magnetic structure and the crystalline micro-structure. Co/FeMn/Co thin films with 0.4 nm Pt spacer layer inserted into the Co/FeMn and FeMn/Co interface respectively were deposited by means of magnetron sputtering. The two interfaces upon and beneath the FeMn layer show distinct behaviors before and after the Pt spacer inserted. There is a remarkable shrink of the interracial uncompensated spins within the FeMn bottom interracial monolayers, whereas a relaxation of the pinning strength of the FeMn interfacial spins along the out-of-plane direction occurs at the top in- terface. XRD analysis indicates the Pt layer upon the FeMn layer forms an fcc （002） texture, implying the magnetic discrepancy between the top and bottom FeMn interfaces has crystalline structural origins.

Effects and Mechanism of Titanium Modification on Structures of Cast Steel ZG270-500

The influences of titanium modification on the solidification behavior, shrinkage characteristic and primary austenite refinement of cast steel ZG270-500 smelted in intermediate frequency induction furnace were studied. 0.15wt% titanium modification increased the fluidity of the steel liquid, enhanced the feeding capacity of cast steel, changed the dispersed shrinkage porosity to concentrated shrinkage cavity, turned the coarse dendrites into fine equiaxed grain structures and greatly reduced the primary austenite grain size. By scanning electron microscope （SEM） and energy disperse spectroscope （EDS） analysis, it was found that titanium combined with carbon to be solid phase particles TiC, with high melting point, to promote the primary austenite nucleation authentically by non-spontaneous nucleating. The crystal lattice match growing model between γ–Fe and TiC was established. The mechanism of TiC heterogeneous nucleating existed in that the primary austenite grew up by {111}γ-Fe parallel to the closest packed plane {111}TiC in the crystal orientation 110γ-Fe//211TiC. The crystal planes mismatch and the lowest orientation mismatchδ110γ-Fe 110TiC were 8.18%. and 2.25% respectively, almost achieving complete coherent lattice match growing of austenite on TiC.

Interface characteristics between TiN and matrix and their effect on solidification structure

Heterogeneous nucleation is an effective way to promote the dispersion and precipitation of second-phase particles in steel and refine the grain size of the solidification structure.Not only refining as-cast structure grain size,but TiN in ferritic stainless steel can also pin grain boundaries and restrain the overgrowth of grains during rolling.The interface characteristics between TiN and heterogeneous phases(high-melting inclusions and ferrite phase)were studied based on the wetting angles between molten steel with different compositions and TiN substrate,and on the matching degree between TiN and ferrite lattice.It was found that,for the molten steel with the same composition,the wetting angle with the TiN substrate was significantly smaller than the contact angles with the other three substrates,while the wetting angle between ferrite phase and TiN was the smallest.The lattice matching was compared among MgAl_(2)O_(4),TiN andδmatrix by means of a high-resolution transmission electron microscope,which revealed that a coherent or semi-coherent interface was formed between the crystal plane(400)of MgAl_(2)O_(4)and the crystal plane(200)of TiN,as well as between the crystal plane(200)of TiN and the crystal plane(110)ofδmatrix,with a lattice misfit of 5.1%and 3.4%,respectively.Finally,these two characteristics between TiN and ferrite phase were both explained from the perspective of interfacial energy.The microstructure refinement mechanism from high temperature to room temperature can be better reflected by the proposed wetting–lattice misfit theory.

晶格匹配驱动的二氧化钛纳米线与金属有机框架的定向组装应用于可逆光致变色

开发新型光致变色(PCSS)材料,发展可擦写式光打印技术,是解决能源和环境问题的重要途径.本文报道了一种高效、可逆光致变色材料,即一种由富缺陷态超细TiO_(2)纳米线和金属有机框架材料普鲁士蓝(PB)自发定向组装形成的TiO_(2)/PB介晶材料.TiO_(2)和PB具有不同的晶体结构特征,诱导其定向组装的驱动力在于:TiO_(2)的(001)晶面和PB的(222)晶面具有相似的晶面间距,即“晶格匹配”机制.这种有序组装结构促进了TiO_(2)/PB间的电子传输,实现了紫外光照射下5秒内的快速光打印.TiO_(2)/PB光打印纸同时具有高的分辨率(∼5µm),在重复打印超过100次仍保持对比度基本不变,是已报道最好的光打印纸之一.超细TiO_(2)纳米线同时富含氧空位和钛空位,可实现可见光和太阳光打印.基于密度泛函理论计算,我们提出了一种配体介导的金属有机框架材料与无机材料的定向组装机制,为开发高效PCSS系统及其他先进材料提供了新的思路.

具有近红外区域光信号处理功能的多级枝杈结构有机微米线的精确制备

复杂的多级微纳米结构是集成光电子器件的基本组成部分,然而其精确制备依然面临着巨大的挑战.本文基于有机近红外发光材料DHNBP,利用简易的溶液自组装方法首次成功制备了多级枝杈型有机微米线晶体.在不同的制备条件下,该类多级枝杈结构的集成度也会随之变化.生长机理研究表明(100)晶面和(010)晶面完美的晶格匹配(晶格失配率低至5.3%)起到了至关重要的作用.得益于晶体中分子的单向排列模式,无论是单一微米线还是多级枝杈型微米线都具有优异的光学性质.另外,本文进一步展示了该多级枝杈型微米线作为光学逻辑门及光信号处理器的应用.本文所展示的多级枝杈型有机微纳晶体有可能会进一步推动集成光电子器件的发展.

Block-layer model for intergrowth structures

Lattice match and charge transfer between distinct block layers(BLs)play an important role in the formation of an intergrowth structure.Herein we propose a simple BL model addressing the different roles of the lattice match and the charge transfer.Inter-BL charge transfer lowers the internal energy,while lattice match minimizes the elastic energy,both of which together make the intergrowth structure stabilized.The model is able to reproduce the lattice parameters precisely for complex iron-based superconductors with intergrowth structures.The elastic energy and the charge-transfer energy are evaluated with assistance of the first-principles calculations.This work rationalizes the basic principles of BL design for intergrowth structures,which can be utilized not only for finding new superconducting materials but also for investigating other layered materials with various functionalities.

The X-ray diffraction study of epitaxial La_(0.67)Sr_(0.33)MnO_(3）single crystal thin film

THE colossal magnetoresistance (CMR) effects in doped perovskite-like oxide have stimulatedconsiderable attention to the study of fundamental physics and the application of new type ma-terials. It was reported that a large CMR effect and a high critical temperature T_c shown