Submission Deadline： 10 December 2010Since the introduction of rough sets in 1982 by Professor Zdzislaw Pawlak, we have witnessed great advances in both theory and applications. In order to promote development of rou...Submission Deadline： 10 December 2010Since the introduction of rough sets in 1982 by Professor Zdzislaw Pawlak, we have witnessed great advances in both theory and applications. In order to promote development of rough sets, we are preparing a special issue on ＂Artificial Intelligence with Rough Sets＂ published by JEST （International）, Journal of Electronic Science and Technology, which is a refereed international journal focusing on IT area. The aim of this special issue is to present the current state of the research in this area, oriented towards both theoretical and applications aspects of rough sets.展开更多
The effect of an electric field E on a narrow quantum ring that contains two electrons and is threaded by a magnetic flux B has been investigated. Localization of the electronic distribution and suppression of the Aha...The effect of an electric field E on a narrow quantum ring that contains two electrons and is threaded by a magnetic flux B has been investigated. Localization of the electronic distribution and suppression of the AharonovBohm oscillation （ABO） are found in the two-electron ring, which are similar to those found in a one-electron ring. However, the period of ABO in a two-electron ring is reduced by half compared with that in a one-electron ring. Furthermore, during the variation of B, the persistent current of the ground state may undergo a sudden change in sign. This change is associated with a singlet-triplet transition and has no counterpart in one-electron rings. For a given E, there exists a threshold of energy. When the energy of the excited state exceeds the threshold, the localization would disappear and the ABO would recover. The value of the threshold is proportional to the magnitude of E. Once the threshold is exceeded, the persistent current is much stronger than the current of the ground state at E=0.展开更多
In spite of their extraordinary performance, AlGaN/GaN high electron mobility transistors （HEMTs） still lack solid reliability. Devices under accelerated DC stress tests （off-state, VDS = 0 state, and on-state step...In spite of their extraordinary performance, AlGaN/GaN high electron mobility transistors （HEMTs） still lack solid reliability. Devices under accelerated DC stress tests （off-state, VDS = 0 state, and on-state step-stress） are investigated to help us identify the degradation mechanisms of the AlGaN/GaN HEMTs. All our findings are consistent with the degradation mechanism based on crystallographic-defect formation due to the inverse piezoelectric effects in Ref. [1] （Joh J and del Alamo J A 2006 IEEE IDEM Tech. Digest p. 415）. However, under the on-state condition, the devices are suffering from both inverse piezoelectric effects and hot electron effects, and so to improve the reliability of the devices both effects should be taken into consideration.展开更多
The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numeric...The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numerical simulation. Experiments have been carried out to deter- mine the spatial distribution of electric field by using FEM software and the electronic excitation temperature in discharge by calculating ratio of two relative intensities of atomic spectral lines. In this work, we choose seven Ar atomic emission lines at 415.86 nm [（3s^23p^5）5p →（3s^23p^5）4s] and 706.7 nm, 714.7 nm, 738.4 nm, 751.5 nm, 794.8 nm and 800.6 nm [（3s^23p^5）4p → （3s^23p^5）4s] to estimate the excitation temperature under a Boltzmann approximation. The average electron energy is evaluated in each discharge by using line ratio of 337.1 nm （N2（C^3Пu →B3Пg）） to 391.4 nm （N2^＋（B2 ∑u^＋→ ∑g^＋））. Furthermore, variations of the electronic excitation tempera- ture are presented versus dielectric thickness and dielectric materials. The discharge is stable and uniform along the axial direction, and the electronic excitation temperature at the edge of the copper electrode is the largest. The corresponding average electron energy is in the range of 1.6- 5.1 eV and the electric field is in 1.7-3.2 MV/m, when the distance from copper electrode varies from 0 cm to 6 cm. Moreover, the electronic excitation temperature with a higher permittivity leads to a higher dissipated electrical power.展开更多
Electronic structures of the artificial molecule comprising two truncated pyramidal quantum dots vertically coupled and embedded in the matrix are theoretically analysed via the finite element method. When the quantum...Electronic structures of the artificial molecule comprising two truncated pyramidal quantum dots vertically coupled and embedded in the matrix are theoretically analysed via the finite element method. When the quantum dots are completely aligned, the electron energy levels decrease with the horizontally applied electric field. However, energy levels may have the maxima at non-zero electric field if the dots are staggered by a distance of several nanometers in the same direction of the electric field. In addition to shifting the energy levels, the electric field can also manipulate the electron wavefunctions confined in the quantum dots, in company with the non-perfect alignment.展开更多
The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and grow...The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration （Nd） is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.展开更多
oscale devices.In the present work,we investigate the electronic structures of germanane/antimonene vdW heterostructure in response to normal strain and an external electric field by using the first-principles calcula...oscale devices.In the present work,we investigate the electronic structures of germanane/antimonene vdW heterostructure in response to normal strain and an external electric field by using the first-principles calculations based on density functional theory(DFT).The results demonstrate that the germanane/antimonene vdW heterostructure behaves as a metal in a[1,,0.6]V/A range,while it is a direct semiconductor in a[0.5,0.2]V/A range,and it is an indirect semiconduc-tor in a[0.3,1.0]V/A range.Interestingly,the band alignment of germanane/antimonene vdW heterostructure appears astype-II feature both in a[0.5,0.1]range and in a[0.3,1]V/A range,while it shows the type-I character at 0.2 V/A.In ad-dition,we find that the germanane/antimonene vdW heterostructure is an indirect semiconductor both in an in-plane biaxial strain range of[[5%,,3%]and in an in-plane biaxial strain range of[3%,5%],while it exhibits a direct semiconductor character in an in-plane biaxial strain range of[2%,2%].Furthermore,the band alignment of the germanane/antimonene vdW heterostructure changes from type-II to type-I at an in-plane biaxial strain of 3%.The adjustable electronic structure of this germanane/antimonene vdW heterostructure will pave the way for developing the nanoscale devices.展开更多
The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination a...The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape(i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zero-gap transitions. The energy-gap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.展开更多
Based on the non-equilibrium Green＇s function formalism and first-principles calculations, we investigate the electronic transport properties of an anthracene-based molecular switch with two carbon nanotube electrode...Based on the non-equilibrium Green＇s function formalism and first-principles calculations, we investigate the electronic transport properties of an anthracene-based molecular switch with two carbon nanotube electrodes. Our results show that different terminations at the carbon nanotube end strongly affect the transport properties of the switch. In the case of H-termination the current at low biases is dominated by non-resonant tunneling. In the N-termination case the current at low biases is dominated by quasi-resonant tunneling and is increased by several orders of magnitude. The enhancement is discussed by the molecular projected self-consistent Hamiltonian level, transmission function, and local density of states.展开更多
Since decades,the global electricity demand shows only one direction：a considerable constant increase every year.But the unlimited growth in energy consumption is discussed increasingly critical,not only primarily in...Since decades,the global electricity demand shows only one direction：a considerable constant increase every year.But the unlimited growth in energy consumption is discussed increasingly critical,not only primarily in terms of limitations but also in terms of more efficient,more intelligent,and more sustainable usage of energy.Energy-efficient technologies（EET）and renewable energy technologies are already in a competitive position in different markets,and they are also activelyembedded in scientific research. Meanwhile, enormous research on key points, such as smart home, smart cities, smart environments, and smart living in general, have been executed. Applying EET to improve human well-being and to reduce energy and resource consumption is on focus.展开更多
As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen （CEA） threatens human health seriously ali over the globe. Fast electrical and highly sensitive detec...As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen （CEA） threatens human health seriously ali over the globe. Fast electrical and highly sensitive detection of the CEA with A1GaN/GaN high electron mobility transistor is demonstrated experimentally. To achieve a low detection limit, the Au-gated sensing area of the sensor is functionalized with a CEA aptamer instead of the corresponding antibody. The proposed aptasensor has successfully detected different concentrations （ranging from 50picogram/milliliter （pg/ml） to 50 nanogram/milliliter （ng/ml）） of CEA and achieved a detection limit as low as 50pg/ml at Vas = 0.5 V. The drain-source current shows a c/ear increase of 11.5μA under this bias.展开更多
High-energy electron precipitation in the high latitude regions enhances the ionization of the atmosphere,and subsequently increases the atmospheric conductivities and the vertical electric field of the atmosphere nea...High-energy electron precipitation in the high latitude regions enhances the ionization of the atmosphere,and subsequently increases the atmospheric conductivities and the vertical electric field of the atmosphere near the ground as well.The High-Energy Electron Flux(HEEF) data measured by the Fengyun-3 meteorological satellite are analyzed together with the data of nearsurface atmospheric vertical electric field measured at the Russian Vostok Station.Three HEEF enhancements are identified and it is shown that when the HEEF increases to a certain level,the local atmospheric vertical electric field near the ground can increase substantially than usual.The response time of the electric field to HEEF enhancement is about 3.7 to 4 days.展开更多
A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor（HEMT）.An anomalous critical drain-to-gate voltage with a negative temperature coefficient ...A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor（HEMT）.An anomalous critical drain-to-gate voltage with a negative temperature coefficient is observed in the stress sequence,beyond which the HEMT device starts to recover from degradation induced by early lower voltage stress.While the performance degradation featuring the drain current slump stems from electron trapping in the surface or bulk states during low-to-medium bias stress,the recovery is attributed to high field induced electron detrapping.The carrier detrapping mechanism could be helpful for lessening the trapping-related performance degradation of a GaN-based HEMT.展开更多
Local electron mean energy （LEME） has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the pr...Local electron mean energy （LEME） has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the production of charged particles in a primary streamer discharge. Detailed research on the LEME profile in a primary streamer discharge is extremely important for a comprehensive understanding of the local physical mechanism of a streamer. In this study, the LEME profile of the primary streamer discharge in oxygen-nitrogen mixtures with a pin-plate gap of 0.5 cm under an impulse voltage is investigated using a fluid model. The fluid model includes the electron mean energy density equation, as well as continuity equations for electrons and ions and Poisson＇s electric field equation. The study finds that, except in the initial stage of the primary streamer, the LEME in the primary streamer tip tends to increase as the oxygen-nitrogen mole ratio increases and the pressure decreases. When the primary streamer bridges the gap, the LEME in the primary streamer channel is smaller than the first ionization energies of oxygen and nitrogen. The LEME in the primary streamer channel then decreases as the oxygen-nitrogen mole ratio increases and the pressure increases. The LEME in the primary streamer tip is primarily dependent on the reduced electric field with mole ratios of oxygen-nitrogen given in the oxygen-nitrogen mixtures.展开更多
The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro ＆ nano electronic devices. In this paper, planar aluminum electrodes with...The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro ＆ nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2μm to 40 #m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages： （1） a constantly decreasing region （the gap width d 〈5 μm）, where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; （2） a plateau region with a near constant breakdown potential （5 μm〈 d 〈10 μm）; （3） a region for large gaps that adhered to Paschen＇s curve （d 〉10μm）. And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.展开更多
α-MoO_3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO_3 and hydroquinone as structuring agent. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission ...α-MoO_3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO_3 and hydroquinone as structuring agent. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscopy(TEM) were used to analyse the obtained material. The conductivity mechanism of the Molybdenum ordered nanosheets has been investigated using combined complex impedance and modulus formalism.The temperature dependence of the conductivity, which was between 473 and 573 K, is very close to the Arrhenius' law, with an activation energy of 0.76 eV. However, the conductivity of the material increases with temperature. It shows a typical negative temperature coefficient resistance(NTCR) similar to that of a semiconductor. The dielectric properties of the MoO_3 compound have been studied in the temperature range of 473-573 K as well as the frequency range of 10 Hz to 13 MHz. The ac-conductivity for high frequency σac(ω)obeys the universal power law.展开更多
In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field p...In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge.The high electric field near the gate for the complete silicon doping structure is effectively decreased,which makes the surface electric field uniform.The high electric field peak near the drain results from the potential difference between the surface and the depletion regions.Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer.The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain.The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field.展开更多
In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission,...In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam’s cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.展开更多
We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to ba...We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to basically have the same good electric characteristics as the chips on Si substrates.Furthermore,the better heat dissipation of HEMTs on Cu substrates compared to HEMTs on Si substrates is clearly observed by thermoreflectance imaging,showing the promising potential for very high-power and high-temperature operation.This work shows the outstanding ability of HEMT chips on Cu substrates for solving the self-heating effect with the advantages of process simplicity,high yield,and low production requirement.展开更多
To protect mining areas from electrical fire, it is very important to install electrical nre momtormg system to ensure safety in development of mineral resources and for buildings. In this paper, design for electrical...To protect mining areas from electrical fire, it is very important to install electrical nre momtormg system to ensure safety in development of mineral resources and for buildings. In this paper, design for electrical fire monitoring and detection system with optional sensor modules has been proposed. In addition, necessity and suitability of electrical fire monitoring and detection system with optional sensor modules in mining areas have been reviewed. The designed electrical fire monitoring and detection system suit- able for work environment of mining industry is composed by host-computer monitoring software and slave-computer detectors. Monitoring detectors are manufactured by using embedded technology. Exter- nal shells deployed have superior enclosure performances and explosion-proof properties. It is easy to install and maintain the system. In general, the system has reached, or even exceeded standards specified in national standards for performances and appearances of such devices. Test results show application of electrical fire monitoring and detection system can effectively enhance monitoring intensity over the mining areas and provide reliable guarantee to ensure orderly development of mineral resources and to protect physical and property safety of citizens in these areas.展开更多
文摘Submission Deadline： 10 December 2010Since the introduction of rough sets in 1982 by Professor Zdzislaw Pawlak, we have witnessed great advances in both theory and applications. In order to promote development of rough sets, we are preparing a special issue on ＂Artificial Intelligence with Rough Sets＂ published by JEST （International）, Journal of Electronic Science and Technology, which is a refereed international journal focusing on IT area. The aim of this special issue is to present the current state of the research in this area, oriented towards both theoretical and applications aspects of rough sets.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574163）, the Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Collisions, Lanzhou, China.
文摘The effect of an electric field E on a narrow quantum ring that contains two electrons and is threaded by a magnetic flux B has been investigated. Localization of the electronic distribution and suppression of the AharonovBohm oscillation （ABO） are found in the two-electron ring, which are similar to those found in a one-electron ring. However, the period of ABO in a two-electron ring is reduced by half compared with that in a one-electron ring. Furthermore, during the variation of B, the persistent current of the ground state may undergo a sudden change in sign. This change is associated with a singlet-triplet transition and has no counterpart in one-electron rings. For a given E, there exists a threshold of energy. When the energy of the excited state exceeds the threshold, the localization would disappear and the ABO would recover. The value of the threshold is proportional to the magnitude of E. Once the threshold is exceeded, the persistent current is much stronger than the current of the ground state at E=0.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CBA00600)the National Natural Science Foundation of China (Grant No. 61106106)the Fundamental Research Funds for the Central Universities (Grant No. K50510250006)
文摘In spite of their extraordinary performance, AlGaN/GaN high electron mobility transistors （HEMTs） still lack solid reliability. Devices under accelerated DC stress tests （off-state, VDS = 0 state, and on-state step-stress） are investigated to help us identify the degradation mechanisms of the AlGaN/GaN HEMTs. All our findings are consistent with the degradation mechanism based on crystallographic-defect formation due to the inverse piezoelectric effects in Ref. [1] （Joh J and del Alamo J A 2006 IEEE IDEM Tech. Digest p. 415）. However, under the on-state condition, the devices are suffering from both inverse piezoelectric effects and hot electron effects, and so to improve the reliability of the devices both effects should be taken into consideration.
文摘The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numerical simulation. Experiments have been carried out to deter- mine the spatial distribution of electric field by using FEM software and the electronic excitation temperature in discharge by calculating ratio of two relative intensities of atomic spectral lines. In this work, we choose seven Ar atomic emission lines at 415.86 nm [（3s^23p^5）5p →（3s^23p^5）4s] and 706.7 nm, 714.7 nm, 738.4 nm, 751.5 nm, 794.8 nm and 800.6 nm [（3s^23p^5）4p → （3s^23p^5）4s] to estimate the excitation temperature under a Boltzmann approximation. The average electron energy is evaluated in each discharge by using line ratio of 337.1 nm （N2（C^3Пu →B3Пg）） to 391.4 nm （N2^＋（B2 ∑u^＋→ ∑g^＋））. Furthermore, variations of the electronic excitation tempera- ture are presented versus dielectric thickness and dielectric materials. The discharge is stable and uniform along the axial direction, and the electronic excitation temperature at the edge of the copper electrode is the largest. The corresponding average electron energy is in the range of 1.6- 5.1 eV and the electric field is in 1.7-3.2 MV/m, when the distance from copper electrode varies from 0 cm to 6 cm. Moreover, the electronic excitation temperature with a higher permittivity leads to a higher dissipated electrical power.
基金supported by the National High Technology Research and Development Program of China (Grant No. 2009AA03Z405)the National Natural Science Foundation of China (Grant Nos. 60908028 and 60971068)the Fundamental Research Funds for the Central Universities (Grant No. BUPT2009RC0411)
文摘Electronic structures of the artificial molecule comprising two truncated pyramidal quantum dots vertically coupled and embedded in the matrix are theoretically analysed via the finite element method. When the quantum dots are completely aligned, the electron energy levels decrease with the horizontally applied electric field. However, energy levels may have the maxima at non-zero electric field if the dots are staggered by a distance of several nanometers in the same direction of the electric field. In addition to shifting the energy levels, the electric field can also manipulate the electron wavefunctions confined in the quantum dots, in company with the non-perfect alignment.
基金Supported by the National Natural Science Foundation of China under Grant No 61434006
文摘The InGaAs/InAIAs/InP high electron mobility transistor （HEM：F） structures with lattice-matched and pseudo- morphic channels are grown by gas source molecular beam epitaxy. Effects of Si ^-doping condition and growth interruption on the electrical properties are investigated by changing the Si-cell temperature, doping time and growth process. It is found that the optimal Si ^-doping concentration （Nd） is about 5.0 x 1012 cm-2 and the use of growth interruption has a dramatic effect on the improvement of electrical properties. The material structure and crystal interface are analyzed by secondary ion mass spectroscopy and high resolution transmission elec- tron microscopy. An InGaAs/InAiAs/InP HEMT device with a gate length of lOOnm is fabricated. The device presents good pinch-off characteristics and the kink-effect of the device is trifling. In addition, the device exhibits fT = 249 GHa and fmax 〉 400 GHz.
基金Project supported by the National Natural Science Foundation of China(Grant No.11864011).
文摘oscale devices.In the present work,we investigate the electronic structures of germanane/antimonene vdW heterostructure in response to normal strain and an external electric field by using the first-principles calculations based on density functional theory(DFT).The results demonstrate that the germanane/antimonene vdW heterostructure behaves as a metal in a[1,,0.6]V/A range,while it is a direct semiconductor in a[0.5,0.2]V/A range,and it is an indirect semiconduc-tor in a[0.3,1.0]V/A range.Interestingly,the band alignment of germanane/antimonene vdW heterostructure appears astype-II feature both in a[0.5,0.1]range and in a[0.3,1]V/A range,while it shows the type-I character at 0.2 V/A.In ad-dition,we find that the germanane/antimonene vdW heterostructure is an indirect semiconductor both in an in-plane biaxial strain range of[[5%,,3%]and in an in-plane biaxial strain range of[3%,5%],while it exhibits a direct semiconductor character in an in-plane biaxial strain range of[2%,2%].Furthermore,the band alignment of the germanane/antimonene vdW heterostructure changes from type-II to type-I at an in-plane biaxial strain of 3%.The adjustable electronic structure of this germanane/antimonene vdW heterostructure will pave the way for developing the nanoscale devices.
基金supported in part by the National Science Council of Taiwan under Grant Nos.NSC 96-2221-E-492-007-MY3 and NSC 98-2221-E-006-131-MY3National Center for Theoretical Science(NCTS)in Taiwan
文摘The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape(i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zero-gap transitions. The energy-gap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.
基金Supported by the Natural Science Foundation of Shandong Province under Grant No ZR2009AL004.
文摘Based on the non-equilibrium Green＇s function formalism and first-principles calculations, we investigate the electronic transport properties of an anthracene-based molecular switch with two carbon nanotube electrodes. Our results show that different terminations at the carbon nanotube end strongly affect the transport properties of the switch. In the case of H-termination the current at low biases is dominated by non-resonant tunneling. In the N-termination case the current at low biases is dominated by quasi-resonant tunneling and is increased by several orders of magnitude. The enhancement is discussed by the molecular projected self-consistent Hamiltonian level, transmission function, and local density of states.
文摘Since decades,the global electricity demand shows only one direction：a considerable constant increase every year.But the unlimited growth in energy consumption is discussed increasingly critical,not only primarily in terms of limitations but also in terms of more efficient,more intelligent,and more sustainable usage of energy.Energy-efficient technologies（EET）and renewable energy technologies are already in a competitive position in different markets,and they are also activelyembedded in scientific research. Meanwhile, enormous research on key points, such as smart home, smart cities, smart environments, and smart living in general, have been executed. Applying EET to improve human well-being and to reduce energy and resource consumption is on focus.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFB0400104 and 2016YFB0400301the National Natural Science Foundation of China under Grant No 61334002the National Science and Technology Major Project
文摘As one of the most important tumor-associated antigens of colorectal adenocarcinoma, the carcinoembryonic antigen （CEA） threatens human health seriously ali over the globe. Fast electrical and highly sensitive detection of the CEA with A1GaN/GaN high electron mobility transistor is demonstrated experimentally. To achieve a low detection limit, the Au-gated sensing area of the sensor is functionalized with a CEA aptamer instead of the corresponding antibody. The proposed aptasensor has successfully detected different concentrations （ranging from 50picogram/milliliter （pg/ml） to 50 nanogram/milliliter （ng/ml）） of CEA and achieved a detection limit as low as 50pg/ml at Vas = 0.5 V. The drain-source current shows a c/ear increase of 11.5μA under this bias.
基金Supported by the National Basic Research Program of China(2011CB811404)the Natural Science Foundation of China(40774081)+1 种基金the Specialized Research Fund for State Key LaboratoriesCAS-NSSC-135 project
文摘High-energy electron precipitation in the high latitude regions enhances the ionization of the atmosphere,and subsequently increases the atmospheric conductivities and the vertical electric field of the atmosphere near the ground as well.The High-Energy Electron Flux(HEEF) data measured by the Fengyun-3 meteorological satellite are analyzed together with the data of nearsurface atmospheric vertical electric field measured at the Russian Vostok Station.Three HEEF enhancements are identified and it is shown that when the HEEF increases to a certain level,the local atmospheric vertical electric field near the ground can increase substantially than usual.The response time of the electric field to HEEF enhancement is about 3.7 to 4 days.
文摘A step stress test is carried out to study the reliability characteristics of an AlGaN/GaN high electron mobility transistor（HEMT）.An anomalous critical drain-to-gate voltage with a negative temperature coefficient is observed in the stress sequence,beyond which the HEMT device starts to recover from degradation induced by early lower voltage stress.While the performance degradation featuring the drain current slump stems from electron trapping in the surface or bulk states during low-to-medium bias stress,the recovery is attributed to high field induced electron detrapping.The carrier detrapping mechanism could be helpful for lessening the trapping-related performance degradation of a GaN-based HEMT.
基金Project supported by the Funds for Innovative Research Groups of China (Grant No. 51021005)the National Basic Research Program of China (Grant No. 2009CB724504)the National Natural Science Foundation of China (Grant No. 50707036)
文摘Local electron mean energy （LEME） has a direct effect on the rates of collisional ionization of molecules and atoms by electrons. Electron-impact ionization plays an important role and is the main process for the production of charged particles in a primary streamer discharge. Detailed research on the LEME profile in a primary streamer discharge is extremely important for a comprehensive understanding of the local physical mechanism of a streamer. In this study, the LEME profile of the primary streamer discharge in oxygen-nitrogen mixtures with a pin-plate gap of 0.5 cm under an impulse voltage is investigated using a fluid model. The fluid model includes the electron mean energy density equation, as well as continuity equations for electrons and ions and Poisson＇s electric field equation. The study finds that, except in the initial stage of the primary streamer, the LEME in the primary streamer tip tends to increase as the oxygen-nitrogen mole ratio increases and the pressure decreases. When the primary streamer bridges the gap, the LEME in the primary streamer channel is smaller than the first ionization energies of oxygen and nitrogen. The LEME in the primary streamer channel then decreases as the oxygen-nitrogen mole ratio increases and the pressure increases. The LEME in the primary streamer tip is primarily dependent on the reduced electric field with mole ratios of oxygen-nitrogen given in the oxygen-nitrogen mixtures.
基金supported by Research Funds of State Key Laboratory of Electrical Insulation and Power Equipment (Xi'an Jiaotong University) of China (No.EIPE14107)
文摘The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro ＆ nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2μm to 40 #m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2-3 nA during most of the pre-breakdown period, and then rose rapidly to 10-30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages： （1） a constantly decreasing region （the gap width d 〈5 μm）, where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; （2） a plateau region with a near constant breakdown potential （5 μm〈 d 〈10 μm）; （3） a region for large gaps that adhered to Paschen＇s curve （d 〉10μm）. And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.
文摘α-MoO_3 ordered nanosheets have been synthesized under hydrothermal conditions using commercial MoO_3 and hydroquinone as structuring agent. X-ray diffraction(XRD), scanning electron microscope(SEM) and transmission electron microscopy(TEM) were used to analyse the obtained material. The conductivity mechanism of the Molybdenum ordered nanosheets has been investigated using combined complex impedance and modulus formalism.The temperature dependence of the conductivity, which was between 473 and 573 K, is very close to the Arrhenius' law, with an activation energy of 0.76 eV. However, the conductivity of the material increases with temperature. It shows a typical negative temperature coefficient resistance(NTCR) similar to that of a semiconductor. The dielectric properties of the MoO_3 compound have been studied in the temperature range of 473-573 K as well as the frequency range of 10 Hz to 13 MHz. The ac-conductivity for high frequency σac(ω)obeys the universal power law.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61106076)
文摘In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge.The high electric field near the gate for the complete silicon doping structure is effectively decreased,which makes the surface electric field uniform.The high electric field peak near the drain results from the potential difference between the surface and the depletion regions.Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer.The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain.The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field.
基金Project supported by CAST Innovation Fund (Grant No.CAST-BISEE2019-040)。
文摘In electron beam technology, one of the critical focuses of research and development efforts is on improving the measurement of electron beam parameters. The parameters are closely related to the generation, emission, operation environment, and role of the electron beam and the corresponding medium. In this study, a field calculation method is proposed, and the electric field intensity distribution on the electron beam’s cross-section is analyzed. The characteristics of beam diffusion caused by the space charge effect are investigated in simulation, and the obtained data are compared with the experiment. The simulation demonstrated that the cross-sectional electric field distribution is primarily affected by the electron beam current, current density distribution, and electron beam propagation speed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61704008 and 11574362)。
文摘We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to basically have the same good electric characteristics as the chips on Si substrates.Furthermore,the better heat dissipation of HEMTs on Cu substrates compared to HEMTs on Si substrates is clearly observed by thermoreflectance imaging,showing the promising potential for very high-power and high-temperature operation.This work shows the outstanding ability of HEMT chips on Cu substrates for solving the self-heating effect with the advantages of process simplicity,high yield,and low production requirement.
基金the Science & Technology Research and Development Project of Langfang Municipal City for the Year 2013 (No.2013011048)Baoding GEEHO Electric Technology Development Co.,Ltd.for financial support and help in data acquisition and statistics during preparation of this paper
文摘To protect mining areas from electrical fire, it is very important to install electrical nre momtormg system to ensure safety in development of mineral resources and for buildings. In this paper, design for electrical fire monitoring and detection system with optional sensor modules has been proposed. In addition, necessity and suitability of electrical fire monitoring and detection system with optional sensor modules in mining areas have been reviewed. The designed electrical fire monitoring and detection system suit- able for work environment of mining industry is composed by host-computer monitoring software and slave-computer detectors. Monitoring detectors are manufactured by using embedded technology. Exter- nal shells deployed have superior enclosure performances and explosion-proof properties. It is easy to install and maintain the system. In general, the system has reached, or even exceeded standards specified in national standards for performances and appearances of such devices. Test results show application of electrical fire monitoring and detection system can effectively enhance monitoring intensity over the mining areas and provide reliable guarantee to ensure orderly development of mineral resources and to protect physical and property safety of citizens in these areas.
