In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’d...In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.展开更多
Over the past half-century,significant efforts have been dedicated to the photocatalytic H_(2)production from H_(2)O under UV–visible light irradiation.These endeavors have yielded remarkable results,with efficiency ...Over the past half-century,significant efforts have been dedicated to the photocatalytic H_(2)production from H_(2)O under UV–visible light irradiation.These endeavors have yielded remarkable results,with efficiency levels now approaching near 100%apparent quantum yields,notably utilizing inorganic semiconducting materials such as modified Al-doped SrTiO_(3)photocatalysts.Meanwhile,advancements in organic polymer semiconducting materials,exemplified by g-C_(3)N_(4),have led to substantial improvements in the efficiency of photocatalytic overall water splitting for H_(2)evolution reaction.These improvements,achieved through chemical engineering methods and molecular-level modifications,have resulted in an apparent quantum yield of 69%at 405 nm,accompanied by significant red-shifting of optical absorption to 1400 nm.These developments are presented in chronological order over the past half-century,underscoring the ongoing quest for innovative breakthroughs to enable largescale practical applications of solar hydrogen production.Key considerations in this pursuit include efficiency,stability,cost-effectiveness,and the independent evolution of H_(2)and O_(2).展开更多
Compared to traditional superhard materials with high electron density and short,strong covalent bonds,alloy materials mainly composed of metallic bonding structures typically have great toughness and lower hardness.B...Compared to traditional superhard materials with high electron density and short,strong covalent bonds,alloy materials mainly composed of metallic bonding structures typically have great toughness and lower hardness.Breaking through the limits of alloy materials is a preface and long-term topic,which is of great significance and value for improving the comprehensive mechanical properties of alloy materials.Here,we report on the discovery of a cubic alloy semiconducting material Ti_(2)Co with a large Vickers of hardness K_(v)^(exp)∼6.7GPa and low fracture toughness of K_(IC)^(exp)∼1.51MPa·m^(1/2).Unexpectedly,the K_(v)^(exp)∼6.7GPa is nearly triple of the K_(v)^(cal)∼2.66GPa predicted by density functional theory(DFT)calculations and theK_(IC)^(exp)∼1.51MPa·m^(1/2)is about one or two orders of magnitude smaller than that of ordinary titanium alloy materials(K_(IC)^(exp)∼30-120MPa·m^(1/2)).These specifications place Ti_(2)Co far from the phase space of the known alloy materials.Upon incorporation of oxygen into structural void positions,both values were simultaneously improved for Ti_(4)Co_(2)O to∼9.7GPa and∼2.19MPa·m^(1/2),respectively.Further DFT calculations on the electron localization function of Ti_(4)Co_(2)X(X=B,C,N,O)vs.the interstitial elements indicate that these simultaneous improvements originate from the coexistence of Ti-Co metallic bonds,the emergence of newly oriented Ti-X covalent bonds,and the increase of electron concentration.Moreover,the large difference between K_(v)^(exp)and K_(v)^(cal)of Ti_(2)Co suggests underlying mechanism concerning the absence of the O(16d)or Ti_(2)-O bonds in the O-(Ti_(2))_(6) octahedron.This discovery proposes a new pathway to simultaneously improve the comprehensive mechanical performances and illuminates the path of exploring superconducting materials with excellent mechanical performances.展开更多
Li-doped ZnO thin films had been grown by radio frequency magnetron sputtering and then annealed under various annealing temperatures. The characteristics of ZnO films were examined by XRD, FESEM, Hall measurement and...Li-doped ZnO thin films had been grown by radio frequency magnetron sputtering and then annealed under various annealing temperatures. The characteristics of ZnO films were examined by XRD, FESEM, Hall measurement and optical transmission spectra. Results showed that p type conduction was observed in Li doped ZnO films annealed at 500-600 ℃ and thep type ZnO films possessed a good crystalline with c-axis orientation, dense surface, and average transmission of about 85% in visible spectral region.展开更多
A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic ...A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic force microscopy （AFM）, Hall measurement, and low temperature photoluminescence （PL）. The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40. At this ratio, the root mean square （RMS） roughness of the material is only 2.02 nm; a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm^2/（V.s） and 3.26×10^12cm^-2 respectively. These results are equivalent to those obtained for the same structure grown on InP substrate. There are two peaks in the PL spectrum of the structure, corresponding to two sub-energy levels of the In0.53Ga0.47As quantum well. It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio, for which the reasons are discussed.展开更多
This article describes the growth of zinc sulfide（ZnS） nanorod on glass/aluminum foil by employing butterfly wings as biotemplate. Upon calcinating（at 400 °C）, the butterfly wings soaked in ZnS nanoparticle s...This article describes the growth of zinc sulfide（ZnS） nanorod on glass/aluminum foil by employing butterfly wings as biotemplate. Upon calcinating（at 400 °C）, the butterfly wings soaked in ZnS nanoparticle suspension, with uniform cage-like nanostructures in nanodimensions, were found on glass/aluminum surface. The transverse and longitudinal dimensions of the nanorods were evaluated from scanning electron microscopy micrographs as 132 and 159 nm,respectively. Purity of the ZnS nanorod found on the specimen was checked by recording XRD（28.877°, 48.038°, and57.174°） and Fourier transform infrared spectrometer spectra（663.7 and 551.68 cm^-1）. Luminescence natures of the nanorods were examined using photoluminescence spectral studies. The characteristic emission peak is shown in the visible region with strong intensity, while the excitation peak is shown at 267 nm. Electrochemical impedance spectroscopic analysis of ZnS nanorod exhibits double-layer capacitance value（Cdl= 6.7 nF）, and the Bode plot explains the stability of ZnS nanorod under the influence of electrical field.展开更多
Mo-doped SnO2 （MTO） nanowires are synthesized by an in-situ doping chemical vapour deposition method. Raman scattering spectra indicate that the lattice symmetry of MTO nanowires lowers with the increase of Mo dopin...Mo-doped SnO2 （MTO） nanowires are synthesized by an in-situ doping chemical vapour deposition method. Raman scattering spectra indicate that the lattice symmetry of MTO nanowires lowers with the increase of Mo doping, which implies that Mo ions do enter into the lattice of SnO2 nanowire. Ultraviolet-visible diffuse reflectance spectra show that the band gap of MTO nanowires decreases with the increase of Mo concentration. The photoluminescence emission of SnO2 nanowires around 580~nm at room temperature can also be controlled accurately by Mo-doping, and it is extremely sensitive to Mo ions and will disappear when the atomic ratio reaches 0.46%.展开更多
Photoelectric properties of CdZnTe:In samples with distinctive defect distributions are investigated using various techniques.Samples cut from the head(T04)and tail(W02)regions of a crystal ingot show distinct differe...Photoelectric properties of CdZnTe:In samples with distinctive defect distributions are investigated using various techniques.Samples cut from the head(T04)and tail(W02)regions of a crystal ingot show distinct differences in Te inclusion distribution.Obvious difference is not observed in Fourier transform infrared(FTIR)spectra,UV-Vis-NIR transmittance spectra,and I-V measurements.However,carrier mobility of the tip sample is higher than that of the tail according to the laser beam induced current(LBIC)measurements.Low temperature photoluminescence(PL)measurement presents sharp emission peaks of D^(0)X and A^(0)X,and relatively large peak of D^(0)X(or A^(0)X)/Dcomplex for T04,indicating a better crystalline quality.Thermally stimulated current(TSC)spectrum shows higher density of shallow point defects,i.e.,Cd vacancies,In^(+)_(Cd),etc.,in W02 sample,which could be responsible for the deterioration of electron mobility.展开更多
A chemical-assisted element direct-reaction method is developed to synthesize ZnSe compound semiconductor material at a relatively low temperature （-1000 ℃）. ZnSe polycrystal was obtained in the closed-tube systems...A chemical-assisted element direct-reaction method is developed to synthesize ZnSe compound semiconductor material at a relatively low temperature （-1000 ℃）. ZnSe polycrystal was obtained in the closed-tube systems with Zn-Se, Zn-Se-Zn（NHa）2CI2, ZnoSe-NH4CI and Zn-Se-ZnCI2. The as-synthesized samples were tested by X-ray diffraction （XRD）, thermogravimetric analysis （TGA） and analyzed by thermodynamic numerical method. The results demonstrate that the synthesis efficiency is higher than 99.96% for Zn-Se-ZnCl2 system at around 1000 ℃ for 3 weeks. It also exhibits that not only temperature, but also low apparent ratio of volume and surface area of the source materials and higher ZnCl2 content are required to achieve high synthesis efficiency. A SeCI transporting reaction synthesis process is proposed based on the thermodynamic analysis.展开更多
AlN thin films were deposited on c-,a-and r-plane sapphire substrates by the magnetron sputtering technique.The in-fluence of high-temperature thermal annealing(HTTA)on the structural,optical properties as well as sur...AlN thin films were deposited on c-,a-and r-plane sapphire substrates by the magnetron sputtering technique.The in-fluence of high-temperature thermal annealing(HTTA)on the structural,optical properties as well as surface stoichiometry were comprehensively investigated.The significant narrowing of the(0002)diffraction peak to as low as 68 arcsec of AlN after HTTA implies a reduction of tilt component inside the AlN thin films,and consequently much-reduced dislocation densities.This is also supported by the appearance of E2(high)Raman peak and better Al-N stoichiometry after HTTA.Furthermore,the in-creased absorption edge after HTTA suggests a reduction of point defects acting as the absorption centers.It is concluded that HTTA is a universal post-treatment technique in improving the crystalline quality of sputtered AlN regardless of sapphire orienta-tion.展开更多
The aluminum incorporation efficiencies in nonpolar A-plane and polar C-plane A1GaN films grown by metalorganic vapour phase epitaxy （MOVPE） are investigated. It is found that the aluminum content in A-plane A1GaN f...The aluminum incorporation efficiencies in nonpolar A-plane and polar C-plane A1GaN films grown by metalorganic vapour phase epitaxy （MOVPE） are investigated. It is found that the aluminum content in A-plane A1GaN film is obviously higher than that in the C-plane sample when the growth temperature is above 1070 ℃. The high aluminum incorporation efficiency is beneficial to fabricating deep ultraviolet optoelectronic devices. Moreover, the influences of the gas inlet ratio, the V/Ⅲ ratio, and the chamber pressure on the aluminum content are studied. The results are important for growing the A1GaN films, especially nonpolar A1GaN epilayers.展开更多
Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical an...Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of Zn O thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped Zn O thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped Zn O thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10^（-4） Ω·cm and the highest carrier concentration of 1.86×10^（21） cm^（-3） can be obtained from Zn O thin films with an indium content of 5at% in the target.展开更多
The seminal 1972 demonstration of photocatalytic water splitting marked the advent of a revolutionary low-carbon energy technology capable of harnessing solar radiation for direct hydrogen production through aqueous d...The seminal 1972 demonstration of photocatalytic water splitting marked the advent of a revolutionary low-carbon energy technology capable of harnessing solar radiation for direct hydrogen production through aqueous dissociation [1]. Half a century after this groundbreaking discovery, titanium dioxide(TiO_(2)) continues to occupy a central position in photocatalysis research. This semiconducting material demonstrates a unique combination of advantageous characteristics: outstanding photocatalytic activity, remarkably prolonged charge carrier lifetime, and exceptional photochemical stability against corrosion [2–6].展开更多
Photoluminescence properties of highly p＋-doped GaASl_ySby are investigated. Band gap narrowing （BGN） effect is considered for heavily doped GaAs1_ySby epilayers. Band-gap Eg（GaAsl_ySby）=l.25y2-1.95y＋1.519 is ob...Photoluminescence properties of highly p＋-doped GaASl_ySby are investigated. Band gap narrowing （BGN） effect is considered for heavily doped GaAs1_ySby epilayers. Band-gap Eg（GaAsl_ySby）=l.25y2-1.95y＋1.519 is obtained through fitting band-gap energy obtained by PL spectra from 35 to 300 K. Fermi level （El） and full width at half maximum （FWHM） of photolumines- cence increase with antimony mole fraction. The increase of Fermi level is attributed to hole mass of GaAsl_ySby decrease which is resulted from antimony composition increase. The increase of Fermi level means that more electrons participate in in- direct transition to result in FWHM increases.展开更多
Employing green and economic solvent-free synthesis route, hexagonal iron sulfide （Fe7Ss） nanoflowers were successfully synthesized for the first time. In the experiment, ferric hexadecylxanthate was used as the pre...Employing green and economic solvent-free synthesis route, hexagonal iron sulfide （Fe7Ss） nanoflowers were successfully synthesized for the first time. In the experiment, ferric hexadecylxanthate was used as the precursor, and hexagonal iron sulfide （Fe7Ss） nanoflowers were obtained by thermal decomposition of the precursor at 260 ~C without any additional solvent or inert gas protection. The as-prepared iron sulfide nanoflowers were characterized by means of X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS）. The characterization results indicated that the nanoflowers had uniform size distribution with an average size of about 160 rim. The proposed strategy provides a possible general route for the synthesis of other metal chalcogenide nanostructures.展开更多
Φ55×15 mm~2 CdS bulk single crystal with high infrared transmittance was grown by physical vapor transport. The single crystal has a consistent structure from top to bottom, which was confirmed by X-ray diffract...Φ55×15 mm~2 CdS bulk single crystal with high infrared transmittance was grown by physical vapor transport. The single crystal has a consistent structure from top to bottom, which was confirmed by X-ray diffraction. The(002) full-width at half-maximum of the X-ray diffraction was measured to be 60.00 arcsec, indicating a good quality of the structure. Hall mobility, specific resistivity, and carrier concentration for the top and bottom of the crystal were observed as well. Transmittance for the CdS single crystal was measured to be higher than 70% from 2.5 to 4.5 μm, making the single crystal an important candidate for infrared window materials. Furthermore,the absorption mechanism of the CdS single crystal was analyzed.展开更多
Zinc chalcogenide which includes zinc selenide,zinc sulphide,zinc telluride and mixed crystals of these shows a great potential as an optoelectronic device material. Zinc selenotelluride is a suitable material for vis...Zinc chalcogenide which includes zinc selenide,zinc sulphide,zinc telluride and mixed crystals of these shows a great potential as an optoelectronic device material. Zinc selenotelluride is a suitable material for visible light emitting devices which are expected to cover the spectral range from yellow to blue. In our present study the composition controlled ZnSe1-xTex films with different Te content x = 0,0.2,0.4,0.6,0.8 and 1.0 were deposited by electron beam (EB) evaporation technique. GaAs films were deposited by vacuum evaporation route on indium tin oxide (ITO) substrates which were used as base for depositing the ZnSe1-xTex film. The band-gap energy change in the entire composition range was determined at room temperature by photoluminescence (PL) spectroscopy. The peak observed at about 2.56 eV shows the effect of solid solution formation between ZnSe and ZnTe which modifies the lattice and consequently the band edge emission characteristics. The heterostructures showed three peaks in the visible region of white light spectrum.展开更多
Five-period AlGaSb/GaSb multiple quantum wells（MQW） are grown on a GaSb buffer.Through optimizing the AlSb nucleation layer,the low threading dislocation density of the MQW is found to be（2.50±0.91）×10~8...Five-period AlGaSb/GaSb multiple quantum wells（MQW） are grown on a GaSb buffer.Through optimizing the AlSb nucleation layer,the low threading dislocation density of the MQW is found to be（2.50±0.91）×10~8 cm^（-2） in 1-μm GaSb buffer,as determined by plan-view transmission election microscopy（TEM） images.High resolution TEM clearly shows the presence of 90°misfit dislocations with an average spacing of 5.4 nm at the AlSb/GaAs interface,which effectively relieve most of the strain energy.In the temperature range from T = 26 K to 300 K,photoluminescence of the MQW is dominated by the ground state electron to ground state heavy hole（el-hhl） transition, while a high energy shoulder clearly seen at T76 K can be attributed to the ground state electron to ground state light hole（el-lhl） transition.展开更多
3D hybrid organic-inorganic halide perovskites attract considerable attention due to their outstanding physical properties and promising applications in photovoltaics and light-emitting diodes.Lead-based hybrid perovs...3D hybrid organic-inorganic halide perovskites attract considerable attention due to their outstanding physical properties and promising applications in photovoltaics and light-emitting diodes.Lead-based hybrid perovskites are currently the most studied and applied materials;however,the very high toxicity of lead creates the demand for less toxic lead-free analogues.This paper describes the synthesis and detailed characterization of new 3D tin-based hybrid perovskites with an aziridinium cation(AzrH)SnX_(3)(where AzrH=aziridinium and X=Cl,Br or I).All of the obtained perovskites undergo temperature-induced crystallographic phase transitions at low temperatures.(AzrH)SnBr_(3) and(AzrH)SnI_(3) are cubic at room temperature,while upon cooling,they transit into an orthorhombic phase.(AzrH)SnCl_(3) is orthorhombic at room temperature and reduces its symmetry to two different monoclinic phases upon two consequent transitions.Crystallographic experiments allowed us to obtain ordered structures of the aziridinium cation for the first time.UV-vis measurements showed that(AzrH)SnX_(3) perovskites exhibit absorption edges,characteristic of semiconducting materials.The optical band gaps of the obtained compounds were found to be 3.48 eV(Cl),2.46 eV(Br)and 1.54 eV(I)according to Tauc plots.Thus,the discovered compounds form a new group of 3D semiconducting lead-free perovskites that can widen the range of suitable materials for the production of solar cells and light-emitting diodes.展开更多
文摘In this paper a fully parametrized finite element simulation model of the stator bar end is created using the COMSOL Multiphysics.The model allows conducting the comparison of different corona protection structures’design,various materials properties,and finally optimizing the corona protection system.Several samples of SiC based nonlinear conductivity materials for corona protection were fabricated in laboratory and then investigated.The conductivity dependencies on electric field(0.05 to 1 kV/mm)and temperature(20 to 155℃)were measured.By comparing the heat-resistant grades of the corona protection material and the insulating material,the maximum working temperature of the corona protection material corresponds to the heat-resistant grade F of the insulating material.As the temperature increases,the nonlinear characteristics of the corona protection material in the experiment decrease dramatically,reducing the heat-resistant grade of the corona protection material.The decrease in the nonlinear characteristics of the corona protection material at the maximum operating temperature causes the maximum electric field strength at the end of the HV rotating machines end corona protection(ECP)exceeding the corona discharge electric field strength,resulting in corona phenomenon.
文摘Over the past half-century,significant efforts have been dedicated to the photocatalytic H_(2)production from H_(2)O under UV–visible light irradiation.These endeavors have yielded remarkable results,with efficiency levels now approaching near 100%apparent quantum yields,notably utilizing inorganic semiconducting materials such as modified Al-doped SrTiO_(3)photocatalysts.Meanwhile,advancements in organic polymer semiconducting materials,exemplified by g-C_(3)N_(4),have led to substantial improvements in the efficiency of photocatalytic overall water splitting for H_(2)evolution reaction.These improvements,achieved through chemical engineering methods and molecular-level modifications,have resulted in an apparent quantum yield of 69%at 405 nm,accompanied by significant red-shifting of optical absorption to 1400 nm.These developments are presented in chronological order over the past half-century,underscoring the ongoing quest for innovative breakthroughs to enable largescale practical applications of solar hydrogen production.Key considerations in this pursuit include efficiency,stability,cost-effectiveness,and the independent evolution of H_(2)and O_(2).
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1408400,2023YFA1406100,2023YFA1607400,2022YFA1403800,and 2022YFA1403203)the National Natural Science Foundation of China(Grant Nos.12474055,12404067,12025408,52025026,and U23A6003)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33000000)the Chinese Academy of Sciences President’s International Fellowship Initiative(Grant No.2024PG0003)the Outstanding Member of Youth Promotion Association of Chinese Academy of Sciences(Grant No.Y2022004)supported by the CAC station of Synergetic Extreme Condition User Facility(SECUF,https://cstr.cn/31123.02.SECUF)。
文摘Compared to traditional superhard materials with high electron density and short,strong covalent bonds,alloy materials mainly composed of metallic bonding structures typically have great toughness and lower hardness.Breaking through the limits of alloy materials is a preface and long-term topic,which is of great significance and value for improving the comprehensive mechanical properties of alloy materials.Here,we report on the discovery of a cubic alloy semiconducting material Ti_(2)Co with a large Vickers of hardness K_(v)^(exp)∼6.7GPa and low fracture toughness of K_(IC)^(exp)∼1.51MPa·m^(1/2).Unexpectedly,the K_(v)^(exp)∼6.7GPa is nearly triple of the K_(v)^(cal)∼2.66GPa predicted by density functional theory(DFT)calculations and theK_(IC)^(exp)∼1.51MPa·m^(1/2)is about one or two orders of magnitude smaller than that of ordinary titanium alloy materials(K_(IC)^(exp)∼30-120MPa·m^(1/2)).These specifications place Ti_(2)Co far from the phase space of the known alloy materials.Upon incorporation of oxygen into structural void positions,both values were simultaneously improved for Ti_(4)Co_(2)O to∼9.7GPa and∼2.19MPa·m^(1/2),respectively.Further DFT calculations on the electron localization function of Ti_(4)Co_(2)X(X=B,C,N,O)vs.the interstitial elements indicate that these simultaneous improvements originate from the coexistence of Ti-Co metallic bonds,the emergence of newly oriented Ti-X covalent bonds,and the increase of electron concentration.Moreover,the large difference between K_(v)^(exp)and K_(v)^(cal)of Ti_(2)Co suggests underlying mechanism concerning the absence of the O(16d)or Ti_(2)-O bonds in the O-(Ti_(2))_(6) octahedron.This discovery proposes a new pathway to simultaneously improve the comprehensive mechanical performances and illuminates the path of exploring superconducting materials with excellent mechanical performances.
基金Funded by the Natural Science Foundation of Liaoning,China(No.201204916)Training Programme Foundation for the Talents by the Education Bureau of Liaoning Province,China(No.LJQ2013068)+1 种基金Key Program of Ministry of Education,China(No.212031)Liaoning College Creative Team(No.LT2013014)
文摘Li-doped ZnO thin films had been grown by radio frequency magnetron sputtering and then annealed under various annealing temperatures. The characteristics of ZnO films were examined by XRD, FESEM, Hall measurement and optical transmission spectra. Results showed that p type conduction was observed in Li doped ZnO films annealed at 500-600 ℃ and thep type ZnO films possessed a good crystalline with c-axis orientation, dense surface, and average transmission of about 85% in visible spectral region.
文摘A series of metamorphic high electron mobility transistors （MMHEMTs） with different Ⅴ/Ⅲ flux ratios are grown on CaAs （001） substrates by molecular beam epitaxy （MBE）. The samples are analysed by using atomic force microscopy （AFM）, Hall measurement, and low temperature photoluminescence （PL）. The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40. At this ratio, the root mean square （RMS） roughness of the material is only 2.02 nm; a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm^2/（V.s） and 3.26×10^12cm^-2 respectively. These results are equivalent to those obtained for the same structure grown on InP substrate. There are two peaks in the PL spectrum of the structure, corresponding to two sub-energy levels of the In0.53Ga0.47As quantum well. It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio, for which the reasons are discussed.
文摘This article describes the growth of zinc sulfide（ZnS） nanorod on glass/aluminum foil by employing butterfly wings as biotemplate. Upon calcinating（at 400 °C）, the butterfly wings soaked in ZnS nanoparticle suspension, with uniform cage-like nanostructures in nanodimensions, were found on glass/aluminum surface. The transverse and longitudinal dimensions of the nanorods were evaluated from scanning electron microscopy micrographs as 132 and 159 nm,respectively. Purity of the ZnS nanorod found on the specimen was checked by recording XRD（28.877°, 48.038°, and57.174°） and Fourier transform infrared spectrometer spectra（663.7 and 551.68 cm^-1）. Luminescence natures of the nanorods were examined using photoluminescence spectral studies. The characteristic emission peak is shown in the visible region with strong intensity, while the excitation peak is shown at 267 nm. Electrochemical impedance spectroscopic analysis of ZnS nanorod exhibits double-layer capacitance value（Cdl= 6.7 nF）, and the Bode plot explains the stability of ZnS nanorod under the influence of electrical field.
基金supported by the Major Research Plan of National Natural Science Foundation of China (Grant No. 90606010)the Program for New Century Excellent Talents in University, China (Grant No. NCET-07-0278)+1 种基金the Hunan Provincial Natural Science Fund, China (Grant No. 08JJ1001)the Scientific Research Fund of Hunan Normal University, China (Grant No. 070623)
文摘Mo-doped SnO2 （MTO） nanowires are synthesized by an in-situ doping chemical vapour deposition method. Raman scattering spectra indicate that the lattice symmetry of MTO nanowires lowers with the increase of Mo doping, which implies that Mo ions do enter into the lattice of SnO2 nanowire. Ultraviolet-visible diffuse reflectance spectra show that the band gap of MTO nanowires decreases with the increase of Mo concentration. The photoluminescence emission of SnO2 nanowires around 580~nm at room temperature can also be controlled accurately by Mo-doping, and it is extremely sensitive to Mo ions and will disappear when the atomic ratio reaches 0.46%.
基金Project supported by the National Natural Science Foundations of China(Grant Nos.51502244,51702271,U1631116,and 51372205)the National Key Research and Development Program of China(Grant Nos.2016YFF0101301 and 2016YFE0115200)+2 种基金the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University,China(Grant No.SKLSP201741)the Natural Science Basic Research Plan in Shaanxi Province,China(Grant No.2016KJXX-09)the Fundamental Research Funds for the Central Universities,China(Grant No.3102015BJ(II)ZS014)
文摘Photoelectric properties of CdZnTe:In samples with distinctive defect distributions are investigated using various techniques.Samples cut from the head(T04)and tail(W02)regions of a crystal ingot show distinct differences in Te inclusion distribution.Obvious difference is not observed in Fourier transform infrared(FTIR)spectra,UV-Vis-NIR transmittance spectra,and I-V measurements.However,carrier mobility of the tip sample is higher than that of the tail according to the laser beam induced current(LBIC)measurements.Low temperature photoluminescence(PL)measurement presents sharp emission peaks of D^(0)X and A^(0)X,and relatively large peak of D^(0)X(or A^(0)X)/Dcomplex for T04,indicating a better crystalline quality.Thermally stimulated current(TSC)spectrum shows higher density of shallow point defects,i.e.,Cd vacancies,In^(+)_(Cd),etc.,in W02 sample,which could be responsible for the deterioration of electron mobility.
基金supports of the National Natural Science Foundation of Chinathe National 973 Project (No. 2011CB610406)+1 种基金the Research Fund of Young Teachers for the Doctoral Program of Higher Education of China (No. 20106102120016)the Independent Subject of State Key Laboratory of Solidification Processing (74-QP-2011)
文摘A chemical-assisted element direct-reaction method is developed to synthesize ZnSe compound semiconductor material at a relatively low temperature （-1000 ℃）. ZnSe polycrystal was obtained in the closed-tube systems with Zn-Se, Zn-Se-Zn（NHa）2CI2, ZnoSe-NH4CI and Zn-Se-ZnCI2. The as-synthesized samples were tested by X-ray diffraction （XRD）, thermogravimetric analysis （TGA） and analyzed by thermodynamic numerical method. The results demonstrate that the synthesis efficiency is higher than 99.96% for Zn-Se-ZnCl2 system at around 1000 ℃ for 3 weeks. It also exhibits that not only temperature, but also low apparent ratio of volume and surface area of the source materials and higher ZnCl2 content are required to achieve high synthesis efficiency. A SeCI transporting reaction synthesis process is proposed based on the thermodynamic analysis.
基金supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2020298)National Key Scientific Instrument and Equipment Development Projects of China(YJKYYQ20190074)+2 种基金National Natural Science Foundation of China(61974149)Primary Research and Development Plan of Zhejiang Province(2020C01145)the Natural Science Foundation of Zhejiang Province(LQ21F040004)。
文摘AlN thin films were deposited on c-,a-and r-plane sapphire substrates by the magnetron sputtering technique.The in-fluence of high-temperature thermal annealing(HTTA)on the structural,optical properties as well as surface stoichiometry were comprehensively investigated.The significant narrowing of the(0002)diffraction peak to as low as 68 arcsec of AlN after HTTA implies a reduction of tilt component inside the AlN thin films,and consequently much-reduced dislocation densities.This is also supported by the appearance of E2(high)Raman peak and better Al-N stoichiometry after HTTA.Furthermore,the in-creased absorption edge after HTTA suggests a reduction of point defects acting as the absorption centers.It is concluded that HTTA is a universal post-treatment technique in improving the crystalline quality of sputtered AlN regardless of sapphire orienta-tion.
基金supported by the National Natural Science Foundation of China(Grant Nos.61504128,61504129,61274041,and 11275228)the National Basic Research Program of China(Grant No.2012CB619305)+1 种基金the National High Technology Research and Development Program of China(Grant Nos.2014AA032603,2014AA032609,and 2015AA010801)the Guangdong Provincial Scientific and Technologic Planning Program,China(Grant No.2014B010119002)
文摘The aluminum incorporation efficiencies in nonpolar A-plane and polar C-plane A1GaN films grown by metalorganic vapour phase epitaxy （MOVPE） are investigated. It is found that the aluminum content in A-plane A1GaN film is obviously higher than that in the C-plane sample when the growth temperature is above 1070 ℃. The high aluminum incorporation efficiency is beneficial to fabricating deep ultraviolet optoelectronic devices. Moreover, the influences of the gas inlet ratio, the V/Ⅲ ratio, and the chamber pressure on the aluminum content are studied. The results are important for growing the A1GaN films, especially nonpolar A1GaN epilayers.
基金Funded by the Fundamental Research Fund for the Central Universities(No.CDJXS10102207)the National Natural Science Foundation of China(Nos.11075314,11404302 and 50942021)+2 种基金the Natural Science Foundation of Chongqing City(2011BA4031)the Third Stage of“211”Innovative Talent Training Project(No.S-09109)the Sharing Fund of Large-scale Equipment of Chongqing University(Nos.2010063072 and 2010121556)
文摘Indium doped Zn O films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of Zn O thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped Zn O thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped Zn O thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10^（-4） Ω·cm and the highest carrier concentration of 1.86×10^（21） cm^（-3） can be obtained from Zn O thin films with an indium content of 5at% in the target.
文摘The seminal 1972 demonstration of photocatalytic water splitting marked the advent of a revolutionary low-carbon energy technology capable of harnessing solar radiation for direct hydrogen production through aqueous dissociation [1]. Half a century after this groundbreaking discovery, titanium dioxide(TiO_(2)) continues to occupy a central position in photocatalysis research. This semiconducting material demonstrates a unique combination of advantageous characteristics: outstanding photocatalytic activity, remarkably prolonged charge carrier lifetime, and exceptional photochemical stability against corrosion [2–6].
文摘Photoluminescence properties of highly p＋-doped GaASl_ySby are investigated. Band gap narrowing （BGN） effect is considered for heavily doped GaAs1_ySby epilayers. Band-gap Eg（GaAsl_ySby）=l.25y2-1.95y＋1.519 is obtained through fitting band-gap energy obtained by PL spectra from 35 to 300 K. Fermi level （El） and full width at half maximum （FWHM） of photolumines- cence increase with antimony mole fraction. The increase of Fermi level is attributed to hole mass of GaAsl_ySby decrease which is resulted from antimony composition increase. The increase of Fermi level means that more electrons participate in in- direct transition to result in FWHM increases.
基金the National Natural Science Foundation of China，the Joint Talent Cultivation Funds of NSFC-HN，the New Century Excellent Talents in University，the Scientific Research Foundation of Henan University
文摘Employing green and economic solvent-free synthesis route, hexagonal iron sulfide （Fe7Ss） nanoflowers were successfully synthesized for the first time. In the experiment, ferric hexadecylxanthate was used as the precursor, and hexagonal iron sulfide （Fe7Ss） nanoflowers were obtained by thermal decomposition of the precursor at 260 ~C without any additional solvent or inert gas protection. The as-prepared iron sulfide nanoflowers were characterized by means of X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS）. The characterization results indicated that the nanoflowers had uniform size distribution with an average size of about 160 rim. The proposed strategy provides a possible general route for the synthesis of other metal chalcogenide nanostructures.
基金Project supported by the National Natural Science Foundation of China(No.51702297)
文摘Φ55×15 mm~2 CdS bulk single crystal with high infrared transmittance was grown by physical vapor transport. The single crystal has a consistent structure from top to bottom, which was confirmed by X-ray diffraction. The(002) full-width at half-maximum of the X-ray diffraction was measured to be 60.00 arcsec, indicating a good quality of the structure. Hall mobility, specific resistivity, and carrier concentration for the top and bottom of the crystal were observed as well. Transmittance for the CdS single crystal was measured to be higher than 70% from 2.5 to 4.5 μm, making the single crystal an important candidate for infrared window materials. Furthermore,the absorption mechanism of the CdS single crystal was analyzed.
文摘Zinc chalcogenide which includes zinc selenide,zinc sulphide,zinc telluride and mixed crystals of these shows a great potential as an optoelectronic device material. Zinc selenotelluride is a suitable material for visible light emitting devices which are expected to cover the spectral range from yellow to blue. In our present study the composition controlled ZnSe1-xTex films with different Te content x = 0,0.2,0.4,0.6,0.8 and 1.0 were deposited by electron beam (EB) evaporation technique. GaAs films were deposited by vacuum evaporation route on indium tin oxide (ITO) substrates which were used as base for depositing the ZnSe1-xTex film. The band-gap energy change in the entire composition range was determined at room temperature by photoluminescence (PL) spectroscopy. The peak observed at about 2.56 eV shows the effect of solid solution formation between ZnSe and ZnTe which modifies the lattice and consequently the band edge emission characteristics. The heterostructures showed three peaks in the visible region of white light spectrum.
基金supported by the National Natural Science Foundation of China(No.50572120)the National High Technology Research and Development Program of China(No.2009AA033101)the State Key Development for Basic Research of China(No.2010CB327501).
文摘Five-period AlGaSb/GaSb multiple quantum wells（MQW） are grown on a GaSb buffer.Through optimizing the AlSb nucleation layer,the low threading dislocation density of the MQW is found to be（2.50±0.91）×10~8 cm^（-2） in 1-μm GaSb buffer,as determined by plan-view transmission election microscopy（TEM） images.High resolution TEM clearly shows the presence of 90°misfit dislocations with an average spacing of 5.4 nm at the AlSb/GaAs interface,which effectively relieve most of the strain energy.In the temperature range from T = 26 K to 300 K,photoluminescence of the MQW is dominated by the ground state electron to ground state heavy hole（el-hhl） transition, while a high energy shoulder clearly seen at T76 K can be attributed to the ground state electron to ground state light hole（el-lhl） transition.
基金financial support from the Ministry of Education and Science of Ukraine(grants No 22BF037-03 and 22BF037-09).
文摘3D hybrid organic-inorganic halide perovskites attract considerable attention due to their outstanding physical properties and promising applications in photovoltaics and light-emitting diodes.Lead-based hybrid perovskites are currently the most studied and applied materials;however,the very high toxicity of lead creates the demand for less toxic lead-free analogues.This paper describes the synthesis and detailed characterization of new 3D tin-based hybrid perovskites with an aziridinium cation(AzrH)SnX_(3)(where AzrH=aziridinium and X=Cl,Br or I).All of the obtained perovskites undergo temperature-induced crystallographic phase transitions at low temperatures.(AzrH)SnBr_(3) and(AzrH)SnI_(3) are cubic at room temperature,while upon cooling,they transit into an orthorhombic phase.(AzrH)SnCl_(3) is orthorhombic at room temperature and reduces its symmetry to two different monoclinic phases upon two consequent transitions.Crystallographic experiments allowed us to obtain ordered structures of the aziridinium cation for the first time.UV-vis measurements showed that(AzrH)SnX_(3) perovskites exhibit absorption edges,characteristic of semiconducting materials.The optical band gaps of the obtained compounds were found to be 3.48 eV(Cl),2.46 eV(Br)and 1.54 eV(I)according to Tauc plots.Thus,the discovered compounds form a new group of 3D semiconducting lead-free perovskites that can widen the range of suitable materials for the production of solar cells and light-emitting diodes.
