Herein,a physical and mathematical model of the voltage−current characteristics of a p−n heterostructure with quantum wells(QWs)is prepared using the Sah−Noyce−Shockley(SNS)recombination mechanism to show the SNS reco...Herein,a physical and mathematical model of the voltage−current characteristics of a p−n heterostructure with quantum wells(QWs)is prepared using the Sah−Noyce−Shockley(SNS)recombination mechanism to show the SNS recombination rate of the correction function of the distribution of QWs in the space charge region of diode configuration.A comparison of the model voltage−current characteristics(VCCs)with the experimental ones reveals their adequacy.The technological parameters of the structure of the VCC model are determined experimentally using a nondestructive capacitive approach for determining the impurity distribution profile in the active region of the diode structure with a profile depth resolution of up to 10Å.The correction function in the expression of the recombination rate shows the possibility of determining the derivative of the VCCs of structures with QWs with a nonideality factor of up to 4.展开更多
Metal halide perovskite solar cells(PSCs)have drawn enormous attention due to their great potential to share the market of silicon solar cells[1–3].During the past few years,significant progress has been made in fabr...Metal halide perovskite solar cells(PSCs)have drawn enormous attention due to their great potential to share the market of silicon solar cells[1–3].During the past few years,significant progress has been made in fabrication method,chemical composition,defect passivation,and strain regulation of perovskite materials,making PSCs one of the most promising solution-processed photovoltaic technologies with high efficiency and low cost[4–6].展开更多
To explore the effect of temperature on the phase transformation of HCP→FCC during compression, the uniaxial compression process of AZ31 magnesium alloy was simulated by the molecular dynamics method, and the changes...To explore the effect of temperature on the phase transformation of HCP→FCC during compression, the uniaxial compression process of AZ31 magnesium alloy was simulated by the molecular dynamics method, and the changes of crystal structure and dislocation evolution were observed. The effects of temperature on mechanical properties, crystal structure, and dislocation evolution of magnesium alloy during compression were analyzed. It is concluded that some of the Shockley partial dislocation is related to FCC stacking faults. With the help of TEM characterization, the correctness of the correlation between some of the dislocations and FCC stacking faults is verified. Through the combination of simulation and experiment, this paper provides an idea for the in-depth study of the solid-phase transformation of magnesium alloys and provides reference and guidance for the design of magnesium alloys with good plasticity and formability at room temperature.展开更多
The mechanism of low-temperature deformation in a fracture process of Ll2 Ni3Al is studied by molecular dynamic simulations. Owing to the unstable stacking energy, the [011] superdislocation is dissociated into partia...The mechanism of low-temperature deformation in a fracture process of Ll2 Ni3Al is studied by molecular dynamic simulations. Owing to the unstable stacking energy, the [011] superdislocation is dissociated into partial dislocations separated by a stacking fault. The simulation results show that when the crack speed is larger than a critical speed, the Shockley partial dislocations will break forth from both the crack tip and the vicinity of the crack tip; subsequently the super intrinsic stacking faults are formed in adjacent {111} planes, meanwhile the super extrinsic stacking faults and twinning also occur. Our simulation results suggest that at low temperatures the ductile fracture in Ll2 Ni3Al is accompanied by twinning, which is produced by super-intrinsic stacking faults formed in adjacent {111} planes.展开更多
The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor i...The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor is explored starting from a quadratic ansatz. Rank one and logarithmic dependencies are then envisaged based on considerations from the statistical theory of dislocations. The rele- vance of the presented free energy potentials is evaluated from the corresponding analytical solutions of the periodic two-phase laminate problem under shear where one layer is a single crystal material undergoing single slip and the second one remains purely elastic.展开更多
Dislocation behaviors are analyzed in AlGaN/GaN multiple-quantum-well films grown with different strain-modified interlayers.In the case of multiple-quantum-well layers grown on a GaN buffer layer without the interlay...Dislocation behaviors are analyzed in AlGaN/GaN multiple-quantum-well films grown with different strain-modified interlayers.In the case of multiple-quantum-well layers grown on a GaN buffer layer without the interlayer,many threading dislocations interact and annihilate within about 100 nm below the multiple quantum well layer.For multiple-quantum-well layers grown with the AlGaN interlayer,misfit dislocations between the GaN buffer layer and the AlGaN interlayer enter multiple-quantum-well layers and result in an increase of threading dislocation density.Besides misfit dislocations,the edge-type dislocation is another dislocation origin attributed to the dissociation of Shockley partials bounding the stacking fault in AlN/GaN superlattices below the interlayer interface.展开更多
Electrical and optical properties of InGaN/AlGaN double heterostructure blue light-emitting diodes were investigated.Measurement of the forward bias current-voltage behaviour of the device demonstrated a departure fro...Electrical and optical properties of InGaN/AlGaN double heterostructure blue light-emitting diodes were investigated.Measurement of the forward bias current-voltage behaviour of the device demonstrated a departure from the Shockley model of a p-n diode,and it was observed that the dominant mechanism of carrier transport across the junction is associated with carrier tunnelling.Electroluminescence experiments indicated that there was a main emission band around 2.80 eV and a relatively weaker peak at 3.2 eV.A significant blueshift of the optical emission band was observed,which was consistent with the tunnelling character of electrical characteristics.Furthermore,the degradation in I-V characteristics and the low resistance ohmic short of the device were observed.展开更多
The invention of the transistor 75 years ago by American scientists John Bardeen, William Shockley, and Walter Brattain at Bell Labs(New Jersey, USA), was the onset of a technological revolution that has changed the w...The invention of the transistor 75 years ago by American scientists John Bardeen, William Shockley, and Walter Brattain at Bell Labs(New Jersey, USA), was the onset of a technological revolution that has changed the world [1].展开更多
基金conducted within the state assignment of the Ministry of Science and Higher Education for universities(Project No.FZRR-2023-0009).
文摘Herein,a physical and mathematical model of the voltage−current characteristics of a p−n heterostructure with quantum wells(QWs)is prepared using the Sah−Noyce−Shockley(SNS)recombination mechanism to show the SNS recombination rate of the correction function of the distribution of QWs in the space charge region of diode configuration.A comparison of the model voltage−current characteristics(VCCs)with the experimental ones reveals their adequacy.The technological parameters of the structure of the VCC model are determined experimentally using a nondestructive capacitive approach for determining the impurity distribution profile in the active region of the diode structure with a profile depth resolution of up to 10Å.The correction function in the expression of the recombination rate shows the possibility of determining the derivative of the VCCs of structures with QWs with a nonideality factor of up to 4.
基金the Chinese Academy of Sciencesthe National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China(51773045,21772030,51922032,and 21961160720)for financial support。
文摘Metal halide perovskite solar cells(PSCs)have drawn enormous attention due to their great potential to share the market of silicon solar cells[1–3].During the past few years,significant progress has been made in fabrication method,chemical composition,defect passivation,and strain regulation of perovskite materials,making PSCs one of the most promising solution-processed photovoltaic technologies with high efficiency and low cost[4–6].
基金supported by the National Key Research and Development Project (2018YFB1307902)Shanxi Province Joint Student Training Base Talent Training Project(No.2018JD33)+5 种基金Shanxi young top talent projectShanxi Province Science Foundation for Youths (201901D211312)Excellent young academic leaders in Shanxi colleges and universities(No.2019045)Excellent Achievements Cultivation Project of Shanxi Higher Education Institutions(No.2019KJ028)Shanxi Province emerging industry leader talent projectShanxi Graduate Education Innovation Project(No.2019SY482)。
文摘To explore the effect of temperature on the phase transformation of HCP→FCC during compression, the uniaxial compression process of AZ31 magnesium alloy was simulated by the molecular dynamics method, and the changes of crystal structure and dislocation evolution were observed. The effects of temperature on mechanical properties, crystal structure, and dislocation evolution of magnesium alloy during compression were analyzed. It is concluded that some of the Shockley partial dislocation is related to FCC stacking faults. With the help of TEM characterization, the correctness of the correlation between some of the dislocations and FCC stacking faults is verified. Through the combination of simulation and experiment, this paper provides an idea for the in-depth study of the solid-phase transformation of magnesium alloys and provides reference and guidance for the design of magnesium alloys with good plasticity and formability at room temperature.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB605102)the National Natural Science Foundation of China (Grant No 90306016)
文摘The mechanism of low-temperature deformation in a fracture process of Ll2 Ni3Al is studied by molecular dynamic simulations. Owing to the unstable stacking energy, the [011] superdislocation is dissociated into partial dislocations separated by a stacking fault. The simulation results show that when the crack speed is larger than a critical speed, the Shockley partial dislocations will break forth from both the crack tip and the vicinity of the crack tip; subsequently the super intrinsic stacking faults are formed in adjacent {111} planes, meanwhile the super extrinsic stacking faults and twinning also occur. Our simulation results suggest that at low temperatures the ductile fracture in Ll2 Ni3Al is accompanied by twinning, which is produced by super-intrinsic stacking faults formed in adjacent {111} planes.
基金Dr. F.Latourte (EDF Research and Development Division,Les Renardières,Moret-sur-Loing,France) and Dr. J.M.Proix (EDF Research and Development Division,Clamart,France),and the MAI-SN (EDF,Les Renardières,Moret-sur-Loing,France) for stimulating discussions and financial support for part of this study
文摘The dislocation density tensor computed as the cud of plastic distortion is regarded as a new constitutive variable in crystal plasticity. The dependence of the free energy function on the dislocation density tensor is explored starting from a quadratic ansatz. Rank one and logarithmic dependencies are then envisaged based on considerations from the statistical theory of dislocations. The rele- vance of the presented free energy potentials is evaluated from the corresponding analytical solutions of the periodic two-phase laminate problem under shear where one layer is a single crystal material undergoing single slip and the second one remains purely elastic.
基金Supported by the Natural Science Foundation of Heilongjiang Province under Grant No F2007-1the Open Experimentation Program of Beijing Institute of Technology(BJUT-GTS-200904).
文摘Dislocation behaviors are analyzed in AlGaN/GaN multiple-quantum-well films grown with different strain-modified interlayers.In the case of multiple-quantum-well layers grown on a GaN buffer layer without the interlayer,many threading dislocations interact and annihilate within about 100 nm below the multiple quantum well layer.For multiple-quantum-well layers grown with the AlGaN interlayer,misfit dislocations between the GaN buffer layer and the AlGaN interlayer enter multiple-quantum-well layers and result in an increase of threading dislocation density.Besides misfit dislocations,the edge-type dislocation is another dislocation origin attributed to the dissociation of Shockley partials bounding the stacking fault in AlN/GaN superlattices below the interlayer interface.
基金Supported by the National Natural Science Foundation of China under Grant Nos.69806006,69636010,69976017 and 69987001the National High Technology Research&Development Project of China(No.863-715-011-0030).
文摘Electrical and optical properties of InGaN/AlGaN double heterostructure blue light-emitting diodes were investigated.Measurement of the forward bias current-voltage behaviour of the device demonstrated a departure from the Shockley model of a p-n diode,and it was observed that the dominant mechanism of carrier transport across the junction is associated with carrier tunnelling.Electroluminescence experiments indicated that there was a main emission band around 2.80 eV and a relatively weaker peak at 3.2 eV.A significant blueshift of the optical emission band was observed,which was consistent with the tunnelling character of electrical characteristics.Furthermore,the degradation in I-V characteristics and the low resistance ohmic short of the device were observed.
文摘The invention of the transistor 75 years ago by American scientists John Bardeen, William Shockley, and Walter Brattain at Bell Labs(New Jersey, USA), was the onset of a technological revolution that has changed the world [1].
