Isotropic sintering shrinkage of 3D glass-ceramic nanolattices:backbone preforming and mechanical enhancement

There is a perpetual pursuit for free-form glasses and ceramics featuring outstanding mechanical properties as well as chemical and thermal resistance.It is a promising idea to shape inorganic materials in three-dimensional(3D)forms to reduce their weight while maintaining high mechanical properties.A popular strategy for the preparation of 3D inorganic materials is to mold the organic–inorganic hybrid photoresists into 3D micro-and nano-structures and remove the organic components by subsequent sintering.However,due to the discrete arrangement of inorganic components in the organic-inorganic hybrid photoresists,it remains a huge challenge to attain isotropic shrinkage during sintering.Herein,we demonstrate the isotropic sintering shrinkage by forming the consecutive–Si–O–Si–O–Zr–O–inorganic backbone in photoresists and fabricating 3D glass–ceramic nanolattices with enhanced mechanical properties.The femtosecond(fs)laser is used in two-photon polymerization(TPP)to fabricate 3D green body structures.After subsequent sintering at 1000℃,high-quality 3D glass–ceramic microstructures can be obtained with perfectly intact and smooth morphology.In-suit compression experiments and finite-element simulations reveal that octahedral-truss(oct-truss)lattices possess remarkable adeptness in bearing stress concentration and maintain the structural integrity to resist rod bending,indicating that this structure is a candidate for preparing lightweight and high stiffness glass–ceramic nanolattices.3D printing of such glasses and ceramics has significant implications in a number of industrial applications,including metamaterials,microelectromechanical systems,photonic crystals,and damage-tolerant lightweight materials.

Ultrafast Laser-Induced Excellent Thermoelectric Performance of PEDOT:PSS Films

Because poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)is water processable,thermally stable,and highly conductive,PEDOT:PSS and its composites have been considered to be one of the most promising flexible thermoelectric materials.However,the PEDOT:PSS film prepared from its commercial aqueous dispersion usually has very low conductivity,thus cannot be directly utilized for TE applications.Here,a simple environmental friendly strategy via femtosecond laser irradiation without any chemical dopants and treatments was demonstrated.Under optimal conditions,the electrical conductivity of the treated film is increased to 803.1 S cm^(-1)from 1.2 S cm^(-1)around three order of magnitude higher,and the power factor is improved to 19.0μW m^(-1)K^(-2),which is enhanced more than 200 times.The mechanism for such remarkable enhancement was attributed to the transition of the PEDOT chains from a coil to a linear or expanded coil conformation,reduction of the interplanar stacking distance,and the removal of insulating PSS with increasing the oxidation level of PEDOT,facilitating the charge transportation.This work presents an effective route for fabricating high-performance flexible conductive polymer films and wearable thermoelectric devices.

Transcriptomic and proteomic studies of condylar ossification of the temporomandibular joint in porcine embryos

Background:The ossification mechanism of the temporomandibular joint(TMJ)condyle remains unclear in human embryo.The size and structure of TMJ,shape of articular disc and the characteristics of omnivorous chewing in the pig are similar to those of humans.The pig is an ideal animal for studying the mechanism of ossification of the TMJ condyle during the embryonic period.Method:In a previous study by our group,it was found that there was no condylar ossification on embryonic day(E)45,but the ossification of condyle occurred between E75 and E90.In this study,a total of 12 miniature pig embryos on E45 and E85 were used.Six embryos were used for tissue sections(3 in each group).The remaining six embryos were used for transcriptomic and proteomic studies to find differential genes and proteins.The differentially expressed genes in transcriptome and proteomic analysis were verified by QPCR.Results:In total,1592 differential genes comprising 1086 up-regulated genes and 506 down-regulated genes were screened for fold changes of≥2 to≤0.5 between E45 and E85.In the total of 4613 proteins detected by proteomic analysis,there were 419 differential proteins including 313 up-regulated proteins and 106 down-regulated proteins screened for fold changes of≥2 to≤0.5 between E45 and E85.A total of 36 differential genes differing in both transcriptome and proteome analysis were found.QPCR analysis showed that 14 of 15 selected genes were consistent with transcriptome analysis.Conclusion:Condylar transcriptome and proteomic analysis during the development of TMJ in miniature pigs revealed the regulatory genes/proteins of condylar ossification.

Inverse design and realization of an optical cavity-based displacement transducer with arbitrary responses

Optical cavity has long been critical for a variety of applications ranging from precise measurement to spectral analysis.A number of theories and methods have been successful in describing the optical response of a stratified optical cavity,while the inverse problem,especially the inverse design of a displacement sensitive cavity,remains a significant challenge due to the cost of computation and comprehensive performance requirements.This paper reports a novel inverse design methodology combining the characteristic matrix method,mixed-discrete variables optimization algorithm,and Monte Carlo method-based tolerance analysis.The material characteristics are indexed to enable the mixed-discrete variables optimization,which yields considerable speed and efficiency improvements.This method allows arbitrary response adjustment with technical feasibility and gives a glimpse into the analytical characterization of the optical response.Two entirely different light-displacement responses,including an asymmetric sawtooth-like response and a highly symmetric response,are dug out and experimentally achieved,which fully confirms the validity of the method.The compact Fabry-Perot cavities have a good balance between performance and feasibility,making them promising candidates for displacement transducers.More importantly,the proposed inverse design paves the way for a universal design of optical cavities,or even nanophotonic devices.

Survival of transplanted neurotrophin-3 expressing human neural stem cells and motor function in a rat model of spinal cord injury

BACKGROUND： Many methods have been attempted to repair nerves following spinal cord injury, including peripheral nerve transplantation, Schwann cell transplantation, olfactory ensheathing cell transplantation, and embryonic neural tissue transplantation. However, there is a need for improved outcomes. OBJECTIVE： To investigate the repair feasibility for rat spinal cord injury using human neural stem cells （hNSCs） genetically modified by lentivirus to express neurotrophin-3. DESIGN, TIME AND SETTING： In vitro cell biological experiment and in vivo randomized, controlled genetic engineering experiment were performed at the Third Military Medical University of Chinese PLA and First People＇s Hospital of Yibin, China from March 2006 to December 2007. MATERIALS： A total of 64 adult, female, Wistar rats were used for the in vivo study. Of them, 48 rats were used to establish models of spinal cord hemisection, and were subsequently equally and randomly assigned to model, genetically modified hNSC, and normal hNSC groups. The remaining 16 rats served as normal controls. METHODS： hNSCs were in vitro genetically modified by lentivirus to secrete both green fluorescence protein and neurotrophin-3. Neurotrophin-3 expression was measured by Western blot. Genetically modified hNSC or normal hNSC suspension （5 × 10^5） was injected into the rat spinal cord following T10 spinal cord hemisection. A total of 5μL Dulbecco＇s-modified Eagle＇s medium was infused into the rat spinal cord in the model grop. Transgene expression and survival of transplanted hNSCs were determined by immunohistochemistry. Motor function was evaluated using the Basso, Beattie, and Bresnahan （BBB） scale. MAIN OUTCOME MEASURES： The following parameters were measured： expression of neurotrophin-3 produced by genetically modified hNSCs, transgene expression and survival of hNSCs in rats, motor function in rats. RESULTS： hNSCs were successfully genetically modified by lentivirus to stably express neurotrophin-3. The transplanted hNSCs primarily gathered at, or around, the injection site two weeks following transplantation, and gradually migrated towards the surrounding tissue. Transplanted hNSCs were observed 7.0-8.0 mm away from the injection site. In addition, hNSCs were observed 10 weeks after transplantation. At week 4, BBB locomotor scores were significantly greater in the genetically modified hNSC and normal hNSC groups, compared with the model group （P 〈 0.05）, and scores were significantly greater in the genetically modified hNSC group compared with the normal hNSC group （P 〈 0.05）. CONCLUSION： hNSCs were genetically modified with lentivirus to stably secrete neurotrophin-3. hNSCs improved motor function recovery in rats following spinal cord injury.

Expression of neurocan mRNA and ultrastructure of brain tissue after cerebral ischemia and reperfusion in stroke-prone renovascular hypertensive rats treated by electroacupuncture

We established a stroke-prone renovascular hypertensive rat model by bilateral constriction of the renal artery with sliver loop clips. After ten weeks, middle cerebral artery occlusion was induced for 2 hours. The rats then received electro-acupuncture at Baihui （DU 20） and Dazhui （DU 14） after onset of ischemia for 30 days. In situ hybridization study showed that electroacupuncture significantly reduced the number of neurocan mRNA-positive cells in the ischemic penumbra and hippocampal tissues of rats. Electron microscopy results demonstrated that the structure of neurons and blood vessels in the ischemic tissues were restored with electroacupuncture. Overall, these data suggest that electroacupuncture may protect neurons against ischemic reperfusion injury in stroke-prone renovascular hypertensive rats, which may be regulated by downregulation of expression of nerve inhibitory factor neurocan mRNA.

An operation optimization method of a fully mechanized coal mining face based on semi-physical virtual simulation

A mathematical hydraulic support self-tracking model for three-machine cooperative mining is proposed to address low efficiency and difficulties in strategy evaluation of a fully mechanized coal face.The proposed model uses the coordinates and traction speed of the shearer to calculate the frequency of the circular hydraulic support and realize the coordinated operation of the three-machine mining technology.A unity3d hardware-in-the-loop simulation experimental hearer and hydraulic support platform was used to validate the model of autonomous follow-up.The results indicate that collaborative control of coal mining allowed for an efficiency 3.76%higher than under automatic operation mode and 46.03%higher than under manual control;thus,The mathematical model provided an improved production efficiency of the fully mechanized mining face.The mathematical model also provides a more intelligent and reliable security support,and improves the intelligent level of hydraulic support follow-up control.

3D macropore carbon-vacancy g-C_(3)N_(4) constructed using polymethylmethacrylate spheres for enhanced photocatalytic H_(2) evolution and CO_(2) reduction

Metal-free g-C_3N_4 is widely used in photocatalytic reactions owing to its suitable band structure.However, it has low specific surface area and insufficient absorbance for visible light, and its photoexcited carriers have high recombination rates. In this study, the 3 D macropore C-vacancy g-C_3N_4 was prepared through a facile one-step route. Polymethylmethacrylate is used as a template to increase the surface reaction sites of g-C_3N_4 and extend its visible-light range. Compared to unmodified g-C_3N_4, the H2 production and CO_2 reduction rates of the fabricated g-C_3N_4 significantly improved. The special pore structure significantly improved the light utilization efficiency of g-C_3N_4 and increased the number of surface-active sites. The introduction of C-vacancy extended the absorption band of visible-light and suppressed the carrier recombination. The newly developed synthesis strategy can improve solar energy conversion efficiency and potentially modifies g-C_3N_4.

Review of micromachined optical accelerometers:from mg to sub-μg

Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume and anti-electromagnetic disturbance measurement of acceleration.In recent years,with the in-depth research and development of MOEMS accelerometers,the community is flourishing with the possible applications in seismic monitoring,inertial navigation,aerospace and other industrial and military fields.There have been a variety of schemes of MOEMS accelerometers,whereas the performances differ greatly due to different measurement principles and corresponding application requirements.This paper aims to address the pressing issue of the current lack of systematic review of MOEMS accelerometers.According to the optical measurement principle,we divide the MOEMS accelerometers into three categories:the geometric optics based,the wave optics based,and the new optomechanical accelerometers.Regarding the most widely studied category,the wave optics based accelerometers are further divided into four sub-categories,which is based on grating interferometric cavity,Fiber Bragg Grating(FBG),Fabry-Perot cavity,and photonic crystal,respectively.Following a brief introduction to the measurement principles,the typical performances,advantages and disadvantages as well as the potential application scenarios of all kinds of MOEMS accelerometers are discussed on the basis of typical demonstrations.This paper also presents the status and development tendency of MOEMS accelerometers to meet the ever-increasing demand for high-precision acceleration measurement.

Sleep quality improved following a single session of moderate-intensity aerobic exercise in older women:Results from a pilot study

Background： Poor sleep quality is associated with adverse effects on health outcomes. It is not clear whether exercise can improve sleep quality and whether intensity of exercise affects any of the effects. Methods： Fifteen healthy, non-obese （body mass index = 24.4 ± 2.1 kg/m^2, mean 4- SD）, sedentary （〈20 min of exercise on no more than 3 times/week） older women （66.1 ± 3.9 years） volunteered for the study. Peak oxygen consumption （VO2peak） was evaluated using a graded exercise test on a treadmill with a metabolic cart. Following a 7-day baseline period, each participant completed two exercise sessions （separated by 1 week） with equal caloric expenditure, but at different intensities （60% and 45% VO2peak, sequence randomized） between 9：00 and 11：00 am. A wrist ActiGraph monitor was used to assess sleep at baseline and two nights following each exercise session. Results： The average duration of the exercise was 54 and 72 rain, respectively at 60% （moderate-intensity） and 45% VO2peak （light-intensity）. Wake time after sleep onset was significantly shorter （p = 0.016）, the number of awakenings was less （p = 0.046）, and total activity counts were lower （p = 0.05） after the moderate-intensity exercise compared to baseline no-exercise condition. Conclusion： Our data showed that a single moderate-intensity aerobic exercise session improved sleep quality in older women.

Virtual straightening of scraper conveyor based on the position and attitude solution of industrial robot model

The movement of the floating connecting mechanism between a hydraulic support and scraper conveyor is space movement;thus,when the hydraulic support pushes the scraper conveyor,there is an error between the actual distance of the scraper conveyor and the theoretical moving distance.As a result,the scraper conveyor cannot obtain the straightness requirement.Therefore,the movement law of the floating connecting mechanism between the hydraulic support and scraper conveyor is analyzed and programmed into the Unity3D to realize accurate pushing of the scraper conveyor via hydraulic support.The Coal Seam?Equipment Joint Virtual Straightening System is established,and a straightening method based on the motion law of a floating connection is proposed as the default method of the system.In addition,a straightening simulation of the scraper conveyor was performed on a complex coal seam floor,the results demonstrate that the average straightening error of the scraper conveyor is within 2-8 mm,and is in direct proportion to the fluctuation of the coal seam floor in the strike of the seam with high accuracy,the straightness of scraper conveyor is more affected by the subsidence terrain during straightening than by the bulge terrain.And some conclusions are verified by experiment.Based on the verification of the relevant conclusions,a comparison and analysis of Longwall Automation Steering Committee(LASC)straightening technology and default straightening method in the simulation system shows that the straightness accuracy of LASC straightening technology under complex floor conditions is slightly less than that of the default straightening method in the proposed system.

Identification of powdery mildew resistance loci in wheat by integrating genome-wide association study(GWAS) and linkage mapping

Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cultivars is a preferred approach to managing this disease, and novel powdery mildew resistance genes are urgently needed for new cultivar development.A genome-wide association study was performed on a panel of 1292 wheat landraces and historical cultivars using 5011 single nucleotide polymorphism(SNP)markers.The association panel was evaluated for reactions to three Bgt inoculants, OKS(14)-B-3-1, OKS(14)-C-2-1, and Bgt15.Linkage disequilibrum(LD) analysis indicated that genome-wide LD decayed to 0.1 at 23 Mb, and population structure analysis revealed seven subgroups in the panel.Association analysis using a mixed linear model(MLM) identified three loci for powdery mildew resistance on chromosome 2 B, designated QPm.stars-2BL1,QPm.stars-2BL2, and QPm.stars-2BL3.To evaluate the efficacy of GWAS in gene discovery,QPm.stars-2BL2 was validated using F2 and F2:3 populations derived from PI420646 × OK1059060-126135-3.Linkage analysis delimited the powdery mildew resistance gene in PI 420646 to an interval where QPm.stars-2BL2 was located, lending credence to the GWAS results.QPm.stars-2BL1 and QPm.stars-2BL3, which were associated with four SNPs located at 457.7–461.7 Mb and two SNPs located at 696.6–715.9 Mb in the Chinese Spring reference IWGSC RefSeq v1.0, respectively, are likely novel loci for powdery mildew resistance and can be used in wheat breeding to improve powdery mildew resistance.

Spatiotemporal Variations of Microwave Land Surface Emissivity(MLSE)over China Derived from Four-Year Recalibrated Fengyun 3B MWRI Data

Microwave Land Surface Emissivity(MLSE)over China under both clear and cloudy sky conditions was retrieved using measurements of recalibrated microwave brightness temperatures(Tbs)from Fengyun-3B Microwave Radiation Imager(FY-3B MWRI),combined with cloud properties derived from Himawari-8 Advanced Himawari Imager(AHI)observations.The contributions from cloud particles and atmospheric gases to the upwelling Tbs at the top of atmosphere were calculated and removed in radiative transfer.The MLSEs at horizontal polarizations at 10.65,18.7,and 36.5 GHz during 7 July 2015 to 30 June 2019 over China showed high values in the southeast vegetated area and low values in the northwest barren,or sparsely vegetated,area.The maximum values were found in the belt area of the Qinling-Taihang Mountains and the eastern edge of the Qinghai-Tibet Plateau,which is highly consistent with MLSEs derived from AMSR-E.It demonstrates that the measurements of FY-3B MWRI Tbs,including its calibration and validation,are reliable,and the retrieval algorithm developed in this study works well.Seasonal variations of MLSE in China are mainly driven by the combined effects of vegetation,rainfall,and snow cover.In tropical and southern forest regions,the seasonal variation of MLSE is small due to the enhancement from vegetation and the suppression from rainfall.In the boreal area,snow causes a significant decrease of MLSE at 36.5 GHz in winter.Meanwhile,the MLSE at lower frequencies experiences less suppression.In the desert region in Xinjiang,increases of MLSEs at all frequencies are observed with increasing snow cover.

Effect of exercise training intensity on adipose tissue hormone sensitive lipase gene expression in obese women under weight loss

Background:Hormone sensitive lipase(HSL) is an enzyme that regulates adipose tissue lipolysis and plays an important role in chronic exerciseinduced changes in adipose tissue metabolism.The purpose of this study was to determine whether aerobic exercise intensity influences abdominal adipose tissue HSL gene expression in obese women under weight loss. Methods:Thirty women(body mass index(BMI) = 33.0±0.7 kg/m^2,age = 58±1 years) completed one of three 20-week interventions: caloric restriction alone(CR only,n = 8),CR plus moderate-intensity exercise(CR + moderate-intensity,45%—50%heart rate reserve(HRR). 3 day/week,n = 9),or CR plus vigorous-intensity exercise(CR + vigorous-intensity,70%—75%HRR,3 day/week,n = 13).Each group had a similar prescribed energy deficit comprised of underfeeding alone(2800 kcal/week for CR only) or underfeeding(2400 kcal/week) plus exercise(400 kcal/week).Body composition and maximal aerobic capacity(VO_2max) were measured,and subcutaneous abdominal adipose tissue samples were collected before and after the interventions.Adipose tissue HSL gene expression was measured by real time reversetranscriptase polymerase chain reaction. Results:All three interventions reduced body weight,fat mass,percent fat.and waist to a similar degree(all p < 0.01).In addition,all interventions did not change absolute VO_2 max,but increased relative VO_2 max(p < 0.05 to P < 0.01).Compared to pre-intervention.neither CR only nor CR + moderate-intensity changed adipose tissue HSL gene expression,but CR + vigorous-intensity significantly increased adipose tissue HSL gene expression(p < 0.01).The changes of HSL gene expression levels in the CR + vigorous-intensity group were significantly different from those in the CR only(p < 0.05) and CR + moderate-intensity(p < 0.01) groups.In the whole cohort,changes in adipose tissue HSL gene expression correlated positively to changes in absolute(r = 0.55,p < 0.01) and relative(r = 0.32,p = 0.09) VO_2 max. Conclusion:These results support a potential effect of aerobic exercise training intensity on hormone sensitive lipase pathway in adipose tissue metabolism in obese women under weight loss.

Field experiment using transient energy method to locate a single-phase to ground fault

Distribution networks in China and several other countries are predominantly neutral inefficiently grounding systems(NIGSs),and more than 80%of the faults in distribution networks are single-phase-to-ground(SPG)faults.Because of the weak fault current and imperfect monitoring equipment configurations,methods used to determine the faulty line secti ons with SPG faults in NIGSs are in effective.The developme nt and application of distributi on-level phasor measurement units(PMUs)provide further comprehensive fault information for fault diagnosis in a distribution network.When an SPG fault occurs,the transient energy of the faulted line section tends to be higher than the sum of the transient energies of other line sections.In this regard,transient energy-based fault location algorithms appear to be a promising resolution.In this study,a field test plan was designed and implemented for a 10 kV distribution network.The test results dem on strate the effective ness of the transient en ergy-based SPG locati on method in practical distributi on networks.

Flexible and wearable healthcare sensors for visual reality health-monitoring

Visual reality(VR)health-monitoring by flexible electronics provides a new avenue to remote and wearable medicine.The combination of flexible electronics and VR could facilitate smart remote disease diagnosis by real-time monitoring of the physiological signals and remote interaction between patient and physician.The flexible healthcare sensor is the most crucial unit in the flexible and wearable health-monitoring system,which has attracted much attention in recent years.This paper briefly reviews the progress in flexible healthcare sensors and VR healthcare devices.The flexible healthcare sensor is introduced with basic flexible materials,manufacturing techniques,and their applications in health-monitoring(such as blood/sweat detection and heart-rate tracking).VR healthcare devices for telemedicine diagnosis are discussed,and the smart remote diagnosis system using flexible and wearable healthcare sensors,and a VR device,is addressed.

A virtual test and evaluation method for fully mechanized mining production system with diferent smart levels

A smart fully mechanized coal mining working face is comprised of various heterogeneous equipment that work together in unknown coal seam environments.The goal is to form a smart operational system with comprehensive perception,decisionmaking,and control.This involves many work points and complex coupling relationships,indicating it needs to be performed in stages and coordinated to address key problems in all directions and along multiple points.However,there are no existing unifed test or analysis tools.Therefore,this study proposed a virtual test and evaluation method for a fully mechanized mining production system with diferent smart levels.This is based on the concept of“real data processing–virtual scene construction–setting key information points–virtual operation and evaluation.”The actual operational data for a specifc working face geology and equipment were reasonably transformed into a visual virtual scene through a movement relationship model.The virtual operations and mining conditions of the working face were accurately reproduced.Based on the sensor and execution error analyses for diferent smart levels,the input interface for sensing,decision-making,and control was established for each piece of equipment,and an operation evaluation system was constructed.The system comprehensively simulates and tests the key points of sensing decision-making and control with various smart levels.The experimental results showed that the virtual scene constructed based on actual operational data has a high simulation degree.Users can simulate,analyze,and evaluate the overall operations of the smart mining 2.0–4.0 working face by inputting key information.The future direction for the smart development of fully mechanized mining is highlighted.

Synthesis of cobalt-doped ZnO/rGO nanoparticles with visible-light photocatalytic activity through a cobalt-induced electrochemical method

ZnO is a semiconductor photocatalyst widely applied in photodegradation of organic pollutants and in photoelectric conversion. ZnO exhibits low photocatalytic activity due to poor absorption in the visible region. In this work, a novel cobalt-induced electrochemical growth method was developed to synthesize cobalt-doped ZnO/rGO nanoparticles in an aqueous solution at room temperature. Cobalt-doped ZnO/rGO nanoparticles exhibited wider visible-light absorption band ranging from 400 nm to 700 nm due to cobalt doping. The surface structure of ZnO formed by the cobalt-induced electrochemical method without other ions is suitable for photocatalytic reactions. The cobalt-doped ZnO/rGO nanoparticles were found to exhibit in photodegradation and photo-electrochemical measurements and exhibited enhanced photocatalytic activity under visible-light irradiation.

ZnO sheets prepared with a light-assisted growth method for improved photodegradation performance

ZnO as a semiconductor photocatalyst is widely applied in the photodegradation of organic pollutants. Its photocatalytic activity is greatly decreased because of the recombination of photoexcited electrons and holes in the bulk. In this work, ZnO sheets are synthesized by adjusting the NaOH concentration under light irradiation at room temperature. Compared with ZnO particles, the ZnO sheets prepared with a light-assisted growth method exhibit a higher rate of photodegradation of methylene blue under UV visible light irradiation. The improved photodegradation rate is mainly attributed to the shortened transport distance of photoexcited electrons, the high surface area, and the surface atom structure modified by the light-assisted growth process. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Theoretical Study on the Optical and Electrical Properties of Al_<i>x</i>Ga_1-<i>x</i>N Crystals

By making use of the density functional theory (DFT) of the first principles and generalized gradient approximation method, the electronic structures and properties of ideal GaN and AlxGa1-xN crystals (x = 0.25, 0.5, 0.75) have been calculated and analyzed, and the influence of the doping quantity of x on the characteristics of AlxGa1-xN has been studied. The calculation results show that optical band gap of AlxGa1-xN crystal is widened that the Eg of AlxGa1-xN can be adjusted by the x, and the absorption spectrum shifts to high-energy direction with the increase of the x, and then the Fermi energy moves to the top of valence band slightly which leads to that conductivity weakened after mixed with the Al. At the same time, the variation trends of complex dielectric function, absorption spectrum and transitivity have been made clear, and the results show that AlxGa1-xN compounds can achieve the theoretical design of photoelectric performance. In a word, AlxGa1-xN crystals are potential semiconductors with very remarkable photoelectric properties, which can be applied in the development of the diversified GaN devices.