Doped two-dimensional(2D)materials hold significant promise for advancing many technologies,such as microelectronics,optoelectronics,and energy storage.Herein,n-type 2D oxidized Si nanosheets,namely n-type siloxene(n-...Doped two-dimensional(2D)materials hold significant promise for advancing many technologies,such as microelectronics,optoelectronics,and energy storage.Herein,n-type 2D oxidized Si nanosheets,namely n-type siloxene(n-SX),are employed as Li-ion battery anodes.Via thermal evaporation of sodium hypophosphite at 275℃,P atoms are effectively incorporated into siloxene(SX)without compromising its 2D layered morphology and unique Kautsky-type crystal structure.Further,selective nucleophilic substitution occurs,with only Si atoms being replaced by P atoms in the O_(3)≡Si-H tetrahedra.The resulting n-SX possesses two delocalized electrons arising from the presence of two electron donor types:(i)P atoms residing in Si sites and(ii)H vacancies.The doping concentrations are varied by controlling the amount of precursors or their mean free paths.Even at 2000 mA g^(-1),the n-SX electrode with the optimized doping concentration(6.7×10^(19) atoms cm^(-3))delivers a capacity of 594 mAh g^(-1) with a 73%capacity retention after 500 cycles.These improvements originate from the enhanced kinetics of charge transport processes,including electronic conduction,charge transfer,and solid-state diffusion.The approach proposed herein offers an unprecedented route for engineering SX anodes to boost Li-ion storage.展开更多
Bi_(2)Te_(3)-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi_(2)(Te,Se)_(...Bi_(2)Te_(3)-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi_(2)(Te,Se)_(3)materials is still low due to the evaporation energy of Se(37.70 kJ mol^(-1))being much lower than that of Te(52.55 kJ mol^(-1)).The evaporated Se from the material causes problems in interconnects of the module while degrading the efficiency.Here,we have developed a new approach for the high-performance and stable n-type Se-free Bi_(2)Te_(3)-based materials bymaximizing the electronic transport while suppressing the phonon transport,at the same time.Spontaneously generated FeTe_(2)nanoinclusions within the matrix during the melt-spinning and subsequent spark plasma sintering is the key to simultaneous engineering of the power factor and lattice thermal conductivity.The nanoinclusions change the fermi level of the matrix while intensifying the phonon scattering via nanoparticles.With a fine-tuning of the fermi level with Cu doping in the n-type Bi_(2)Te_(3)-0.02FeTe_(2),a high power factor of∼41×10^(-4)Wm^(-1)K^(-2)with an average zT of 1.01 at the temperature range 300-470 K are achieved,which are comparable to those obtained in n-type Bi_(2)(Te,Se)_(3)materials.The proposed approach enables the fabrication of high-performance n-type Bi_(2)Te_(3)-based materials without having to include volatile Se element,which guarantees the stability of the material.Consequently,widespread application of thermoelectric devices utilizing the n-type Bi_(2)Te_(3)-based materials will become possible.展开更多
The spoiler is a kind of device to disturb current and promote burying.At present,all submarine pipeline spoilers at home and abroad are parallel spoilers,that is,the plane of the spoiler is parallel to the vertical p...The spoiler is a kind of device to disturb current and promote burying.At present,all submarine pipeline spoilers at home and abroad are parallel spoilers,that is,the plane of the spoiler is parallel to the vertical plane of the pipeline axis.According to the results of indoor experiments,when the pipeline with the forward spoiler is installed perpendicular to the direction of water flow,the spoiler will accelerate the seabed erosion and cause the pipeline to endure downward pressure,which will eventually cause the pipeline self-buried to form a protection.However,when the pipeline direction is consistent with the flow direction,the self-buried behavior and protective effect is vanished.By aiming at the defect that the forward spoiler cannot be self-buried when the direction of the pipeline and the flow are basically parallel,the spoiler burying aid device perpendicular to the pipeline axis has been innovatively developed,and the hydrodynamic changes and sediment erosion characteristics near the pipeline after the installation of the device were studied based on the experiment.Results reveal that although the perpendicular spoiler cannot generate downforce,it can greatly increase the turbulent kinetic energy of the flow and the rate of sediment erosion.The larger the angle between the pipeline axis and the spoiler plane is,the larger the increase in turbulent energy will be.The increase in turbulent energy near the bed surface can reach up about 70%when the angle is 90°,while serious sediment erosion mainly occurs along both sides of the pipeline with a distance of about 2−4 times the pipe diameter.In the future,we can further explore the influence of the perpendicular spoiler size and installation position on the pipeline downforce and the effect of burying promotion.At the same time,field tests on the perpendicular spoiler burying aid device currently developed will conduct to observe the actual effect of perpendicular spoiler promoting pipeline scouring and burying,and improve submarine pipeline safety protection technology.展开更多
We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion...We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region, which has been known as the positive Doppler effect on optical bistability. In addition, we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type.展开更多
We present a detailed investigation of magnetic properties of colossal magnetoresistance material HgCr2Se4. While spontaneous magnetization and zero-field magnetic susceptibility are found to follow asymptotic scaling...We present a detailed investigation of magnetic properties of colossal magnetoresistance material HgCr2Se4. While spontaneous magnetization and zero-field magnetic susceptibility are found to follow asymptotic scaling laws for a narrow range of temperatures near the critical point, two methods with connections to the renormalization group theory provide analytical descriptions of the magnetic properties for much wider temperature ranges. Based on this, an analytical formula is obtained for the temperature dependence of the low field magnetoresistance in the paramagnetic phase.展开更多
A new super-junction lateral double diffused MOSFET (LDMOST) structure is designed with n-type charge compensation layer embedded in the p^--substrate near the drain to suppress substrate-assisted depletion effect t...A new super-junction lateral double diffused MOSFET (LDMOST) structure is designed with n-type charge compensation layer embedded in the p^--substrate near the drain to suppress substrate-assisted depletion effect that results from the compensating charges imbalance between the pillars in the n-type buried layer. A high electric field peak is introduced in the surface by the pn junction between the p^--substrate and n-type buried layer, which given rise to a more uniform surface electric field distribution by modulation effect. The effect of reduced bulk field (REBULF) is introduced to improve the vertical breakdown voltage by reducing the high bulk electric field around the drain, The new structure features high breakdown voltage, low on-resistance and charges balance in the drift region due to n-type buried layer.展开更多
The lattice, the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by first- principles calculations. The results show that the lattice constants change linearly with stress. Ban...The lattice, the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by first- principles calculations. The results show that the lattice constants change linearly with stress. Band gaps are broadened linearly as the uniaxial compressive stress increases. The change of band gap for n-type ZnO comes mainly from the contribution of stress in the c-axis direction, and the reason for band gap of n-type ZnO changing with stress is also explained. The calculated results of optical properties reveal that the imaginary part of the dielectric function decreases with the increase of uniaxial compressive stress at low energy. However, when the energy is higher than 4.0 eV, the imaginary part of the dielectric function increases with the increase of stress and a blueshift appears. There are two peaks in the absorption spectrum in an energy range of 4.0-13.0 eV. The stress coefficient of the band gap of n-type ZnO is larger than that of pure ZnO, which supplies the theoretical reference value for the modulation of the band gap of doped ZnO.展开更多
The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradati...The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradations on ir- radiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation (STI). The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.展开更多
Thermoelectric(TE)materials based on conjugated polymers have received much attention due to their great advantages of solution processibility,light weight,flexibility,and low thermal conductivity.These advantages mak...Thermoelectric(TE)materials based on conjugated polymers have received much attention due to their great advantages of solution processibility,light weight,flexibility,and low thermal conductivity.These advantages make them potential candidates for large-area,low-cost and low-power TE applications.Both efficient p-type and n-type conjugated polymers with high and comparable thermoelectric performance are required for practical TE applications.However,due to the inefficient n-doping efficiency and unstable electron transport of most n-type conjugated polymers,the TE performance of n-type polymers is much poorer than that of their p-type counterparts,impeding the development of polymer TE materials.Great efforts have been made to address the low ndoping efficiency and TE performance of n-type polymers,including the chemical modification of traditional ntype polymers,the design of new n-type conjugated polymers,and the development of more efficient n-dopants,as well as doping engineering.Nowadays,the TE performance of n-type polymers has been greatly improved,indicating a bright future for polymer TE materials.In this review,we summarize the recent progress made on ntype polymer TE materials,mainly focusing on the structure-performance relationships based on promising n-type polymers for TE applications.This review aims to provide some guidelines for future material design.展开更多
This paper numerically studies the influence of the downward spoiler deflection on the boundary layer flow of a high-lift two-element airfoil consisting of a droop nose, a main wing, a downward deflecting spoiler and ...This paper numerically studies the influence of the downward spoiler deflection on the boundary layer flow of a high-lift two-element airfoil consisting of a droop nose, a main wing, a downward deflecting spoiler and a single slotted flap. Both of the boundary layer of the upper surface of the spoiler and the confluent boundary layer of the upper surface of the flap become thicker, as the downward spoiler deflection increases. Compared to the attached flow at the angle of attack of 10°, the flow of the upper surface of the spoiler becomes separated at the angle of attack of 16° when the spoiler deflection is large enough, which corresponds to the boundary layer flow reversal in velocity profiles.展开更多
In the present paper,numerical solution of the two-dimensional unsteady Navier-Stokes equations is used to study the forced shear flow induced by a spoiler's periodical up and down oscillation on a flat plate.The ...In the present paper,numerical solution of the two-dimensional unsteady Navier-Stokes equations is used to study the forced shear flow induced by a spoiler's periodical up and down oscillation on a flat plate.The paper studies the evolution of growing,shedding,merging and decaying of vortices due to the spoiler's oscillation,particularly the dependence of the forced shear flow on the re- duced frequency.Results show that the reduced frequency is a key factor in controlling the growing and the shedding of vortices in the shear layer.The instantaneous streamlines and the equi-vorticity con- tours,as well as the surface pressure distributions,have also been investigated.Numerical results agree well with corresponding experimental ones.The study is helpful for understanding the physical mecha- nism of shear flow control.展开更多
Upper surface wing flaps, known as spoiler, are typically used to reduce lift and increase drag at touchdown;however spoilers have been shown to increase lift and reduce drag at near-stall conditions. The purpose of t...Upper surface wing flaps, known as spoiler, are typically used to reduce lift and increase drag at touchdown;however spoilers have been shown to increase lift and reduce drag at near-stall conditions. The purpose of this experiment was to determine the spoilers’ impact on lift, drag, moment, and aerodynamic efficiency of a NACA 2412 airfoil at angles of attack (α) from −8 ° to 32 °. The experiment was conducted in the Ryerson Low-Speed Wind Tunnel (closed-circuit, 1 m × 1 m test section) at Re=783761, Ma=0.136. The lift coefficient (Cl), drag coefficient (Cd), moment coefficient about the quarter-chord () were captured with a changing spoiler deflection angle (δ) and spoiler length (b in percent chord). It was found that deflecting the spoiler resulted in an increase maximum lift of up to 2.497%. It was found that deflecting the spoiler by 8° was optimal for the b=10 cases. Any larger deflection reduced the lift gain, and a deflection of 25° caused the maximum lift to be 2.786% less than the clean configuration. In the b=15 case, δ=15° was optimal (1.760% maximum lift coefficient increase). The b=10 cases increased maximum lift coefficient between 0.35% and 2.10% higher than the b=15 cases. The source of the lift gain at high angles of attack is apparent in an analysis of the airfoil pressure distribution. The spoiler increased the suction peak on the airfoil surface upstream of the spoiler, and increased the pressure downstream. However the suction increase upstream is larger than the pressure increase downstream, resulting in a net increase in lift. The spoiler increased the stall angle 37.658% to 87.658% higher than the clean configuration. Stall angle increased with both δ and with an increased spoiler length. The spoiler airfoil produced less drag than the clean configuration at high angles of attack. The combination of the increased lift, and reduced drag resulted in an increase in aerodynamic efficiency at high angle of attack.展开更多
With the growing need on distributed power supply for portable electronics,energy harvesting from environment becomes a promising solution.Organic thermoelectric(TE)materials have advantages in intrinsic flexibility a...With the growing need on distributed power supply for portable electronics,energy harvesting from environment becomes a promising solution.Organic thermoelectric(TE)materials have advantages in intrinsic flexibility and low thermal conductivity,thus hold great prospect in applications as a flexible power generator from dissipated heat.Nevertheless,the weak electrical transport behaviors of organic TE materials have severely impeded their development.Moreover,compared with p-type organic TE materials,stable and high-performance n-type counterparts are more difficult to obtain.Here,we developed a n-type polyaniline-based hybrid with core-shell heterostructured Bi;S;@Bi nanorods as fillers,showing a Seebeck coefficient-159.4μV/K at room temperature.Further,a couple of n/p legs from the PANI-based hybrids were integrated into an elastomer substrate forming a stretchable thermoelectric generator(TEG),whose function to output stable voltages responding to temperature differences has been demonstrated.The in situ output performance of the TEG under stretching could withstand up to 75%elongation,and stability test showed little degradation over a one-month period in the air.This study provides a promising strategy to develop stable and high thermopower organic TEGs harvesting heat from environment as long-term power supply.展开更多
We study the electromagnetically induced-absorption-like(EIA-like) effect for an n-type system in an ^(87)Rb Bose–Einstein condensate(BEC) using the absorption imaging technique for coupling and driving lasers operat...We study the electromagnetically induced-absorption-like(EIA-like) effect for an n-type system in an ^(87)Rb Bose–Einstein condensate(BEC) using the absorption imaging technique for coupling and driving lasers operating at the D_1 and D_2 lines of ^(87)Rb. The coherent effect is probed by measuring the number of atoms remaining after the BEC is exposed to strong driving fields and a weak probe field. The absorption imaging technique accurately reveals the EIA-like effect of the n-type system. This coherent effect in an n-type system is useful for optical storage, tunable optical switching, and so on.展开更多
This paper reports on the n-type ZnS used as electron transport layer for the organic light-emitting diodes (OLEDs). The naphthyl-substituted benzidine derivative (NPB) and tris (8-hydroxyquinoline) aluminium (...This paper reports on the n-type ZnS used as electron transport layer for the organic light-emitting diodes (OLEDs). The naphthyl-substituted benzidine derivative (NPB) and tris (8-hydroxyquinoline) aluminium (Alq3) are used as the hole transport layer and the emitting layer respectively. The insertion of the n-type ZnS layer enhances the electron injection in the OLEDs. The study was carried out on OLEDs of structures: indium-tin-oxide (ITO)/NPB/Alq3/ZnS/LiF/AL, ITO/NPB/Alq3/LiF/AL and ITO/NPB/Alq3/AL. The luminance and efficiency of the device containing this electron transport layer are increased significantly over those obtained from conventional devices due to better carrier balance.展开更多
The effects of the interlayer distance on the nonlinear optical properties of n-type quadrupleδ-doped GaAs quantum well were theoretically investigated.Particularly,the absorption coefficient and the relative refract...The effects of the interlayer distance on the nonlinear optical properties of n-type quadrupleδ-doped GaAs quantum well were theoretically investigated.Particularly,the absorption coefficient and the relative refraction index change were determined.In the effective mass approach and within the framework of the Thomas-Fermi theory,the Schrodinger equation was resolved.Thereby,the subband energy levels and their respective wave functions were calculated.The variations in the nonlinear optical properties were determined by using the density matrix solutions.The achieved results demonstrate that the interlayer distance causes optical red-shift on nonlinear optical properties.Therefore,it can be deduced that the suitably chosen interlayer distance can be used to tune optical properties within the infrared spectrum region in optoelectronic devices such as far-infrared photo-detectors,high-speed electronic-optical modulators,and infrared lasers.展开更多
The effects of ion doses on the properties of boron implanted Si for n-type solar cell application were investigated with doses ranging from 5×10^14cm^-2 to 2×10^15cm^-2 and a subsequent two-step annealing p...The effects of ion doses on the properties of boron implanted Si for n-type solar cell application were investigated with doses ranging from 5×10^14cm^-2 to 2×10^15cm^-2 and a subsequent two-step annealing process in a tube furnace.With the help of the TCAD process simulation tool, knowledge on diffusion kinetics of dopants and damage evolution was obtained by fitting SIMS measured boron profiles. Due to insufficient elimination of the residual damage, the implanted emitter was found to have a higher saturation current density(J0e) and a poorer crystallographic quality. Consistent with this observation, V oc, J sc, and the efficiency of the all-implanted p^+–n–n^+solar cells followed a decreasing trend with an increase of the implantation dose. The obtained maximum efficiency was 19.59% at a low dose of 5×10^14cm^-2. The main efficiency loss under high doses came not only from increased recombination of carriers in the space charge region revealed by double-diode parameters of dark I–V curves, but also from the degraded minority carrier diffusion length in the emitter and base evidenced by IQE data. These experimental results indicated that clusters and dislocation loops had appeared at high implantation doses, which acted as effective recombination centers for photogenerated carriers.展开更多
Poly(nickel 1,1,2,2-ethenetetrathiolate)(poly[Na_(x)(Ni-ett)])is one of the most promising n-type organic thermoelectric materials which can be used in wearable devices.However,the conventional solution method is time...Poly(nickel 1,1,2,2-ethenetetrathiolate)(poly[Na_(x)(Ni-ett)])is one of the most promising n-type organic thermoelectric materials which can be used in wearable devices.However,the conventional solution method is time-consuming and the prepared poly[Na_(x)(Ni-ett)]usually has poor crystallinity,which does not benefit for achieving high thermoelectric performance.Here,a new one-step solvothermal method under the high reaction temperature and high vapor pressure was developed to prepare poly[Na_(x)(Ni-ett)]with a quite short period.The experimental results show crystallinity and electrical conductivity are greatly enhanced as compared with those prepared by conventional solution method.As a result,a maximum ZT value of 0.04 was achieved at 440 K,which is about four times of the polymer prepared by the conventional solution method.This study may provide a new route to enhance the TE properties of n-type organic thermoelectric materials.展开更多
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2020R1A6A1A03045059)+1 种基金by Ministry of Science and ICT(2022R1A2C3003319)by the Institutional Program(2E33221)of the Korea Institute of Science and Technology(KIST).
文摘Doped two-dimensional(2D)materials hold significant promise for advancing many technologies,such as microelectronics,optoelectronics,and energy storage.Herein,n-type 2D oxidized Si nanosheets,namely n-type siloxene(n-SX),are employed as Li-ion battery anodes.Via thermal evaporation of sodium hypophosphite at 275℃,P atoms are effectively incorporated into siloxene(SX)without compromising its 2D layered morphology and unique Kautsky-type crystal structure.Further,selective nucleophilic substitution occurs,with only Si atoms being replaced by P atoms in the O_(3)≡Si-H tetrahedra.The resulting n-SX possesses two delocalized electrons arising from the presence of two electron donor types:(i)P atoms residing in Si sites and(ii)H vacancies.The doping concentrations are varied by controlling the amount of precursors or their mean free paths.Even at 2000 mA g^(-1),the n-SX electrode with the optimized doping concentration(6.7×10^(19) atoms cm^(-3))delivers a capacity of 594 mAh g^(-1) with a 73%capacity retention after 500 cycles.These improvements originate from the enhanced kinetics of charge transport processes,including electronic conduction,charge transfer,and solid-state diffusion.The approach proposed herein offers an unprecedented route for engineering SX anodes to boost Li-ion storage.
基金supported by Nano·Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(2022M3H4A1A04076667)
文摘Bi_(2)Te_(3)-based materials have drawn much attention from the thermoelectric community due to their excellent thermoelectric performance near room temperature.However,the stability of existing n-type Bi_(2)(Te,Se)_(3)materials is still low due to the evaporation energy of Se(37.70 kJ mol^(-1))being much lower than that of Te(52.55 kJ mol^(-1)).The evaporated Se from the material causes problems in interconnects of the module while degrading the efficiency.Here,we have developed a new approach for the high-performance and stable n-type Se-free Bi_(2)Te_(3)-based materials bymaximizing the electronic transport while suppressing the phonon transport,at the same time.Spontaneously generated FeTe_(2)nanoinclusions within the matrix during the melt-spinning and subsequent spark plasma sintering is the key to simultaneous engineering of the power factor and lattice thermal conductivity.The nanoinclusions change the fermi level of the matrix while intensifying the phonon scattering via nanoparticles.With a fine-tuning of the fermi level with Cu doping in the n-type Bi_(2)Te_(3)-0.02FeTe_(2),a high power factor of∼41×10^(-4)Wm^(-1)K^(-2)with an average zT of 1.01 at the temperature range 300-470 K are achieved,which are comparable to those obtained in n-type Bi_(2)(Te,Se)_(3)materials.The proposed approach enables the fabrication of high-performance n-type Bi_(2)Te_(3)-based materials without having to include volatile Se element,which guarantees the stability of the material.Consequently,widespread application of thermoelectric devices utilizing the n-type Bi_(2)Te_(3)-based materials will become possible.
基金This work was financially supported by the National Key Research and Development Plan of China(Grant Nos.2018YFC0407802-3,2018YFC0407803 and 2017YFC0405605)the National Natural Science Foundation of China(Grant No.51909069).
文摘The spoiler is a kind of device to disturb current and promote burying.At present,all submarine pipeline spoilers at home and abroad are parallel spoilers,that is,the plane of the spoiler is parallel to the vertical plane of the pipeline axis.According to the results of indoor experiments,when the pipeline with the forward spoiler is installed perpendicular to the direction of water flow,the spoiler will accelerate the seabed erosion and cause the pipeline to endure downward pressure,which will eventually cause the pipeline self-buried to form a protection.However,when the pipeline direction is consistent with the flow direction,the self-buried behavior and protective effect is vanished.By aiming at the defect that the forward spoiler cannot be self-buried when the direction of the pipeline and the flow are basically parallel,the spoiler burying aid device perpendicular to the pipeline axis has been innovatively developed,and the hydrodynamic changes and sediment erosion characteristics near the pipeline after the installation of the device were studied based on the experiment.Results reveal that although the perpendicular spoiler cannot generate downforce,it can greatly increase the turbulent kinetic energy of the flow and the rate of sediment erosion.The larger the angle between the pipeline axis and the spoiler plane is,the larger the increase in turbulent energy will be.The increase in turbulent energy near the bed surface can reach up about 70%when the angle is 90°,while serious sediment erosion mainly occurs along both sides of the pipeline with a distance of about 2−4 times the pipe diameter.In the future,we can further explore the influence of the perpendicular spoiler size and installation position on the pipeline downforce and the effect of burying promotion.At the same time,field tests on the perpendicular spoiler burying aid device currently developed will conduct to observe the actual effect of perpendicular spoiler promoting pipeline scouring and burying,and improve submarine pipeline safety protection technology.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60978013)the Shanghai Rising Star Project,China (Grant No. 11QA1407400)
文摘We theoretically investigate the Doppler effect on optical bistability in an N-type active Raman gain atomic system inside an optical ring cavity. It is shown that the Doppler effect can greatly enhance the dispersion and thus create the bistable behaviour or greatly increase the bistable region, which has been known as the positive Doppler effect on optical bistability. In addition, we find that a positive Doppler effect can change optical bistability from the hybrid dispersion-gain type to a dispersive type.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61425015,11474330 and 11374337the National Basic Research Program of China under Grant Nos 2012CB921703 and 2015CB921102the Chinese Academy of Sciences
文摘We present a detailed investigation of magnetic properties of colossal magnetoresistance material HgCr2Se4. While spontaneous magnetization and zero-field magnetic susceptibility are found to follow asymptotic scaling laws for a narrow range of temperatures near the critical point, two methods with connections to the renormalization group theory provide analytical descriptions of the magnetic properties for much wider temperature ranges. Based on this, an analytical formula is obtained for the temperature dependence of the low field magnetoresistance in the paramagnetic phase.
基金Project supported by the National Natural Science Foundation of China (Grant No 60436030) and the Key Laboratory for Defence Science and Technology on Military Simulation Integrated Circuits (Grant No 9140C0903010604).
文摘A new super-junction lateral double diffused MOSFET (LDMOST) structure is designed with n-type charge compensation layer embedded in the p^--substrate near the drain to suppress substrate-assisted depletion effect that results from the compensating charges imbalance between the pillars in the n-type buried layer. A high electric field peak is introduced in the surface by the pn junction between the p^--substrate and n-type buried layer, which given rise to a more uniform surface electric field distribution by modulation effect. The effect of reduced bulk field (REBULF) is introduced to improve the vertical breakdown voltage by reducing the high bulk electric field around the drain, The new structure features high breakdown voltage, low on-resistance and charges balance in the drift region due to n-type buried layer.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61076098)the Innovative Foundation for Doctoral Candidate of Jiangsu Province, China (Grant No. CX10B 252Z)
文摘The lattice, the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by first- principles calculations. The results show that the lattice constants change linearly with stress. Band gaps are broadened linearly as the uniaxial compressive stress increases. The change of band gap for n-type ZnO comes mainly from the contribution of stress in the c-axis direction, and the reason for band gap of n-type ZnO changing with stress is also explained. The calculated results of optical properties reveal that the imaginary part of the dielectric function decreases with the increase of uniaxial compressive stress at low energy. However, when the energy is higher than 4.0 eV, the imaginary part of the dielectric function increases with the increase of stress and a blueshift appears. There are two peaks in the absorption spectrum in an energy range of 4.0-13.0 eV. The stress coefficient of the band gap of n-type ZnO is larger than that of pure ZnO, which supplies the theoretical reference value for the modulation of the band gap of doped ZnO.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11475255,U1532261 and 11505282
文摘The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors (nMOSFETs) is investigated. Experimental results show that hot-carrier degradations on ir- radiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation (STI). The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.
基金the financial support of the National Natural Science Foundation of China(No.21625403,21875244,21875241,22075271)。
文摘Thermoelectric(TE)materials based on conjugated polymers have received much attention due to their great advantages of solution processibility,light weight,flexibility,and low thermal conductivity.These advantages make them potential candidates for large-area,low-cost and low-power TE applications.Both efficient p-type and n-type conjugated polymers with high and comparable thermoelectric performance are required for practical TE applications.However,due to the inefficient n-doping efficiency and unstable electron transport of most n-type conjugated polymers,the TE performance of n-type polymers is much poorer than that of their p-type counterparts,impeding the development of polymer TE materials.Great efforts have been made to address the low ndoping efficiency and TE performance of n-type polymers,including the chemical modification of traditional ntype polymers,the design of new n-type conjugated polymers,and the development of more efficient n-dopants,as well as doping engineering.Nowadays,the TE performance of n-type polymers has been greatly improved,indicating a bright future for polymer TE materials.In this review,we summarize the recent progress made on ntype polymer TE materials,mainly focusing on the structure-performance relationships based on promising n-type polymers for TE applications.This review aims to provide some guidelines for future material design.
文摘This paper numerically studies the influence of the downward spoiler deflection on the boundary layer flow of a high-lift two-element airfoil consisting of a droop nose, a main wing, a downward deflecting spoiler and a single slotted flap. Both of the boundary layer of the upper surface of the spoiler and the confluent boundary layer of the upper surface of the flap become thicker, as the downward spoiler deflection increases. Compared to the attached flow at the angle of attack of 10°, the flow of the upper surface of the spoiler becomes separated at the angle of attack of 16° when the spoiler deflection is large enough, which corresponds to the boundary layer flow reversal in velocity profiles.
文摘In the present paper,numerical solution of the two-dimensional unsteady Navier-Stokes equations is used to study the forced shear flow induced by a spoiler's periodical up and down oscillation on a flat plate.The paper studies the evolution of growing,shedding,merging and decaying of vortices due to the spoiler's oscillation,particularly the dependence of the forced shear flow on the re- duced frequency.Results show that the reduced frequency is a key factor in controlling the growing and the shedding of vortices in the shear layer.The instantaneous streamlines and the equi-vorticity con- tours,as well as the surface pressure distributions,have also been investigated.Numerical results agree well with corresponding experimental ones.The study is helpful for understanding the physical mecha- nism of shear flow control.
文摘Upper surface wing flaps, known as spoiler, are typically used to reduce lift and increase drag at touchdown;however spoilers have been shown to increase lift and reduce drag at near-stall conditions. The purpose of this experiment was to determine the spoilers’ impact on lift, drag, moment, and aerodynamic efficiency of a NACA 2412 airfoil at angles of attack (α) from −8 ° to 32 °. The experiment was conducted in the Ryerson Low-Speed Wind Tunnel (closed-circuit, 1 m × 1 m test section) at Re=783761, Ma=0.136. The lift coefficient (Cl), drag coefficient (Cd), moment coefficient about the quarter-chord () were captured with a changing spoiler deflection angle (δ) and spoiler length (b in percent chord). It was found that deflecting the spoiler resulted in an increase maximum lift of up to 2.497%. It was found that deflecting the spoiler by 8° was optimal for the b=10 cases. Any larger deflection reduced the lift gain, and a deflection of 25° caused the maximum lift to be 2.786% less than the clean configuration. In the b=15 case, δ=15° was optimal (1.760% maximum lift coefficient increase). The b=10 cases increased maximum lift coefficient between 0.35% and 2.10% higher than the b=15 cases. The source of the lift gain at high angles of attack is apparent in an analysis of the airfoil pressure distribution. The spoiler increased the suction peak on the airfoil surface upstream of the spoiler, and increased the pressure downstream. However the suction increase upstream is larger than the pressure increase downstream, resulting in a net increase in lift. The spoiler increased the stall angle 37.658% to 87.658% higher than the clean configuration. Stall angle increased with both δ and with an increased spoiler length. The spoiler airfoil produced less drag than the clean configuration at high angles of attack. The combination of the increased lift, and reduced drag resulted in an increase in aerodynamic efficiency at high angle of attack.
基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0702100 and 2018YFB0703600)the National Natural Science Foundation of China(Grant Nos.51872009 and 92066203)+1 种基金Beijing Nova Programme Interdisciplinary Cooperation Projectthe Fundamental Research Funds for the Central Universities,China。
文摘With the growing need on distributed power supply for portable electronics,energy harvesting from environment becomes a promising solution.Organic thermoelectric(TE)materials have advantages in intrinsic flexibility and low thermal conductivity,thus hold great prospect in applications as a flexible power generator from dissipated heat.Nevertheless,the weak electrical transport behaviors of organic TE materials have severely impeded their development.Moreover,compared with p-type organic TE materials,stable and high-performance n-type counterparts are more difficult to obtain.Here,we developed a n-type polyaniline-based hybrid with core-shell heterostructured Bi;S;@Bi nanorods as fillers,showing a Seebeck coefficient-159.4μV/K at room temperature.Further,a couple of n/p legs from the PANI-based hybrids were integrated into an elastomer substrate forming a stretchable thermoelectric generator(TEG),whose function to output stable voltages responding to temperature differences has been demonstrated.The in situ output performance of the TEG under stretching could withstand up to 75%elongation,and stability test showed little degradation over a one-month period in the air.This study provides a promising strategy to develop stable and high thermopower organic TEGs harvesting heat from environment as long-term power supply.
基金the National Key Research and Development Program of China under Grant No 2016YFA0301602the National Natural Science Foundation of China under Grant Nos 11474188 and 11704234the Fund for Shanxi ‘1331 Project’ Key Subjects Construction,and the Program of Youth Sanjin Scholar
文摘We study the electromagnetically induced-absorption-like(EIA-like) effect for an n-type system in an ^(87)Rb Bose–Einstein condensate(BEC) using the absorption imaging technique for coupling and driving lasers operating at the D_1 and D_2 lines of ^(87)Rb. The coherent effect is probed by measuring the number of atoms remaining after the BEC is exposed to strong driving fields and a weak probe field. The absorption imaging technique accurately reveals the EIA-like effect of the n-type system. This coherent effect in an n-type system is useful for optical storage, tunable optical switching, and so on.
基金Project supported by the National Natural Science Foundation of China (Grant No 60476005), the Scientific Research Foundation for Returned 0verseas Chinese Scholars, the State Education Ministry, the State Key Program for Basic Research of the Ministry of Science and Technology of China (Grant No 2003CB314707), and the Key Project of National Natural Science Foundation of China (Grant No 50532090).
文摘This paper reports on the n-type ZnS used as electron transport layer for the organic light-emitting diodes (OLEDs). The naphthyl-substituted benzidine derivative (NPB) and tris (8-hydroxyquinoline) aluminium (Alq3) are used as the hole transport layer and the emitting layer respectively. The insertion of the n-type ZnS layer enhances the electron injection in the OLEDs. The study was carried out on OLEDs of structures: indium-tin-oxide (ITO)/NPB/Alq3/ZnS/LiF/AL, ITO/NPB/Alq3/LiF/AL and ITO/NPB/Alq3/AL. The luminance and efficiency of the device containing this electron transport layer are increased significantly over those obtained from conventional devices due to better carrier balance.
文摘The effects of the interlayer distance on the nonlinear optical properties of n-type quadrupleδ-doped GaAs quantum well were theoretically investigated.Particularly,the absorption coefficient and the relative refraction index change were determined.In the effective mass approach and within the framework of the Thomas-Fermi theory,the Schrodinger equation was resolved.Thereby,the subband energy levels and their respective wave functions were calculated.The variations in the nonlinear optical properties were determined by using the density matrix solutions.The achieved results demonstrate that the interlayer distance causes optical red-shift on nonlinear optical properties.Therefore,it can be deduced that the suitably chosen interlayer distance can be used to tune optical properties within the infrared spectrum region in optoelectronic devices such as far-infrared photo-detectors,high-speed electronic-optical modulators,and infrared lasers.
基金supported by the National Natural Science Foundation of China(Grant Nos.61275040,60976046,and 61021003)the National Basic Research Program of China(Grant No.2012CB934200)
文摘The effects of ion doses on the properties of boron implanted Si for n-type solar cell application were investigated with doses ranging from 5×10^14cm^-2 to 2×10^15cm^-2 and a subsequent two-step annealing process in a tube furnace.With the help of the TCAD process simulation tool, knowledge on diffusion kinetics of dopants and damage evolution was obtained by fitting SIMS measured boron profiles. Due to insufficient elimination of the residual damage, the implanted emitter was found to have a higher saturation current density(J0e) and a poorer crystallographic quality. Consistent with this observation, V oc, J sc, and the efficiency of the all-implanted p^+–n–n^+solar cells followed a decreasing trend with an increase of the implantation dose. The obtained maximum efficiency was 19.59% at a low dose of 5×10^14cm^-2. The main efficiency loss under high doses came not only from increased recombination of carriers in the space charge region revealed by double-diode parameters of dark I–V curves, but also from the degraded minority carrier diffusion length in the emitter and base evidenced by IQE data. These experimental results indicated that clusters and dislocation loops had appeared at high implantation doses, which acted as effective recombination centers for photogenerated carriers.
基金Fund by the Shanghai Municipal Natural Science Foundation(21ZR1473200)the National Natural Science Foundation of China(No.52072391 and 21905293)。
文摘Poly(nickel 1,1,2,2-ethenetetrathiolate)(poly[Na_(x)(Ni-ett)])is one of the most promising n-type organic thermoelectric materials which can be used in wearable devices.However,the conventional solution method is time-consuming and the prepared poly[Na_(x)(Ni-ett)]usually has poor crystallinity,which does not benefit for achieving high thermoelectric performance.Here,a new one-step solvothermal method under the high reaction temperature and high vapor pressure was developed to prepare poly[Na_(x)(Ni-ett)]with a quite short period.The experimental results show crystallinity and electrical conductivity are greatly enhanced as compared with those prepared by conventional solution method.As a result,a maximum ZT value of 0.04 was achieved at 440 K,which is about four times of the polymer prepared by the conventional solution method.This study may provide a new route to enhance the TE properties of n-type organic thermoelectric materials.