This paper presents a novel scheme for enhancing resistance that utilizes an equivalent negative resistance. Adopting this novel scheme in the proposed current source could remarkably boost its output resistance witho...This paper presents a novel scheme for enhancing resistance that utilizes an equivalent negative resistance. Adopting this novel scheme in the proposed current source could remarkably boost its output resistance without requiring increased power supply. Simulation with 0.6μm CMOS process models shows that the output resistance of the novel current source can reach the order of 10^9Ω with a 1.04GHz bandwidth and only 10.6ppm/℃ in the range of -40～145℃.展开更多
A low-voltage, low-power, and high-gain rail-to-rail operational amplifier （OpAmp） is presented. The replica-amplifier gain enhancement technique is applied to improve the DC gain of the amplifier, which does not de...A low-voltage, low-power, and high-gain rail-to-rail operational amplifier （OpAmp） is presented. The replica-amplifier gain enhancement technique is applied to improve the DC gain of the amplifier, which does not degrade the output swing and is very suitable for low-voltage applications. In a 0. 18/μm standard CMOS process,a 1V OpAmp with rail-to-rail output is designed. For a load capacitance of 5 pF,simulation by HSPICE shows that this OpAmp achieves an effective open-loop DC gain of 65. 9dB,gain bandwidth of 70.28 MHz,and phase margin of 50 with a quiescent power dissipation of 156.7μW.展开更多
A mathematical model is established on the basis of the physical characteristic of the negative resistance arc when a low current of 0—50 A is applied in pulsed TIG welding. The simulation model converted from the ma...A mathematical model is established on the basis of the physical characteristic of the negative resistance arc when a low current of 0—50 A is applied in pulsed TIG welding. The simulation model converted from the mathematical model is run in MATLAB environment, and the discussion is focused on the way the peak current ranging from 29 A to 50 A and the time constant of arc in the span of 0.003—0.006 s influence the simulating results and the dynamic characteristic. The simulating data are close to that of welding experiments and correspond to the theoretical conclusion.展开更多
It is a common misconception that electric “resistance” always is a positive defined electric element. <em>i.e.</em>, the plot of the voltage across the resistor, V vs. its current, i is a slanted straig...It is a common misconception that electric “resistance” always is a positive defined electric element. <em>i.e.</em>, the plot of the voltage across the resistor, V vs. its current, i is a slanted straight line with a positive slope. Esaki diode also known as tunnel diode is an exception to this character. For a certain voltage range, the current recedes resulting in a line with a negative slope;it is interpreted as negative resistance. In this research flavored report, we investigate the impact of the negative resistance in a typical classic electric circuit. E.g., a tunnel diode, D is inserted in a classic electric circuit that is composed of an ohmic resistor, R and a capacitor, C which are all in series with a DC power supply. The circuit equation for the RCD circuit is a nonlinear ordinary differential equation (NLODE). In line with the ever-growing popular Computer Algebra System (CAS), this is solved numerically utilizing two distinctly different CASs. The consistency of the solutions confidently leads to the understanding of the impact of the negative resistance. The circuit characteristics are compared to the classic analogous RC circuit. The report embodies an atlas of characteristics of the circuits making the analysis visually comprehensible.展开更多
The I-V diagram of a tunnel diode inherits a voltage range corresponding to a specific current domain with a negative slope. Within this range, the electric resistance is negatively impacting the characteristics of th...The I-V diagram of a tunnel diode inherits a voltage range corresponding to a specific current domain with a negative slope. Within this range, the electric resistance is negatively impacting the characteristics of the electric circuits. One such circuit containing a tunnel diode in series with an inductor driven by a DC source is considered. The negative resistance significantly alters the characteristics of the circuit. In this research-oriented project, we unveil these characteristics comparing them to the classic inductive circuit with an ohmic resistor. This project stems from our previous work [1] and may be considered an application of the tunnel diode embodying unseen surprises. The circuit analysis is entirely based on utilizing a Computer Algebra System (CAS) specifically Mathematica. Without a CAS, the completion of the project wouldn’t have been possible otherwise.展开更多
The weft-knitted reduced graphene oxide(r-GO)textile that is made up of many conductive r-GO coated fibers was successfully prepared dependent on the electrospray deposition technique.Interestingly,the r-GO textile pr...The weft-knitted reduced graphene oxide(r-GO)textile that is made up of many conductive r-GO coated fibers was successfully prepared dependent on the electrospray deposition technique.Interestingly,the r-GO textile presents negative resistance variation not only in axial direction as the pressure increases but also in transverse direction as the lateral stretch increases which makes it has the advantage to fabricate the reliable sensors based on strain-resistance effect.The transverse-strain and pressure sensors based on the r-GO textiles all show the excellent sensing characteristics such as high sensitivity,reliability,and good durability,etc.The maximum gauge factors(GF)of the transverse-sensor are 27.1 and 153.5 in the x-and/-direction,respectively.And the practical detection range can up to 40%in the x-direction and 35%in the y-direction,respectively.The r-GO textile pressure sensor also shows high sensitivity for a broad pressure range that with a GF up to 716.8 kPa-1 for less than 4.5 kPa region and still has more sensitive pressure sensing characteristics even the pressure goes up to 14 kPa.Based on those good performances of r-GO textile sensors,its potential applications in human body states monitoring have been studied.展开更多
We obtained the output characteristics in wurtzite Al0.15Ga0.85N/GaN MODFETs with the full band Monte Carlo method. The gate length Lg and the channel length Los in the device are 0.2 μm and 0.4 urn, respectively. In...We obtained the output characteristics in wurtzite Al0.15Ga0.85N/GaN MODFETs with the full band Monte Carlo method. The gate length Lg and the channel length Los in the device are 0.2 μm and 0.4 urn, respectively. In the output characteristics we found a differential negative resistance effect. That is, as VDS is a constant, initially, VDS increases with increasing VDS. When VDS exceeds a certain critical value, IDS decreases with increasing VDS. The analysis for velocity-field characteristics in wurtzite CaN, the distributions of the electric field and the electron velocity in the two dimensional electron gas channel indicates that the differential negative resistance effect of the electron average velocity results in the differential negative resistance effect of the output characteristics. The transient transport also is related to the differential negative resistance effect of the output characteristics. This effect only can be observed in the devices with very short channel.展开更多
The electron transport of linear atomic chain trodes was investigated by using the density Green＇s function method. We have calculated of MgB2 sandwiched between Au（100） elecfunctional theory with the non-equilibri...The electron transport of linear atomic chain trodes was investigated by using the density Green＇s function method. We have calculated of MgB2 sandwiched between Au（100） elecfunctional theory with the non-equilibrium the corresponding cohesion energy and conductance of junctions in different distance. It is found that, at the equilibrium position, the Au-B bond-length is 1.90 A, the B-Mg bond-length is 2.22 A, and the equilibrium conductance is 0.51G0 （Go=2e^2/h）. The transport channel is almost formed by the π antibonding orbitals, which was made up of the Px and Py orbital electrons of B and Mg atoms. In the voltage range of -1.5 to 1.5 V, the junctions show the metallic behaviors. When the voltage is larger than 1.5 V, the current decreases gradually and then negative differential resistance appears almost symmetrically on both positive and negative bias.展开更多
We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combin...We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.展开更多
By using first-principles calculations and nonequilibrium Green＇s function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties o...By using first-principles calculations and nonequilibrium Green＇s function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance （NDR） behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.展开更多
Owing to rapid developments in spintronics,spin-based logic devices have emerged as promising tools for next-generation computing technologies.This paper provides a comprehensive review of recent advancements in spin ...Owing to rapid developments in spintronics,spin-based logic devices have emerged as promising tools for next-generation computing technologies.This paper provides a comprehensive review of recent advancements in spin logic devices,particularly focusing on fundamental device concepts rooted in nanomagnets,magnetoresistive random access memory,spin–orbit torques,electric-field modu-lation,and magnetic domain walls.The operation principles of these devices are comprehensively analyzed,and recent progress in spin logic devices based on negative differential resistance-enhanced anomalous Hall effect is summarized.These devices exhibit reconfigur-able logic capabilities and integrate nonvolatile data storage and computing functionalities.For current-driven spin logic devices,negative differential resistance elements are employed to nonlinearly enhance anomalous Hall effect signals from magnetic bits,enabling reconfig-urable Boolean logic operations.Besides,voltage-driven spin logic devices employ another type of negative differential resistance ele-ment to achieve logic functionalities with excellent cascading ability.By cascading several elementary logic gates,the logic circuit of a full adder can be obtained,and the potential of voltage-driven spin logic devices for implementing complex logic functions can be veri-fied.This review contributes to the understanding of the evolving landscape of spin logic devices and underscores the promising pro-spects they offer for the future of emerging computing schemes.展开更多
By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the...By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the electronic transport properties of molecular devices are affected by doped atoms. Negative differential resistance (NDR) behavior can be observed in certain bias regions for C82 and C80BN molecular devices but cannot be observed for C80N2 molecular device. A mechanism for the negative differential resistance behavior was suggested.展开更多
Room-temperature negative differential resistance （NDR） has been observed in different types of organic materials. However, detailed study on the influence of the organic material on NDR performance is still scarce....Room-temperature negative differential resistance （NDR） has been observed in different types of organic materials. However, detailed study on the influence of the organic material on NDR performance is still scarce. In this work, room-temperature NDR ＆ observed when CdSe quantum dot （QD） modified ITO is used as the electrode. Furthermore, material dependence of the NDR performance is observed by selecting materials with different charge transporting properties as the active layer, respectively. A peak-to-valley current ratio up to 9 is observed. It is demonstrated that the injection barrier between ITO and the organic active layer plays a decisive role for the device NDR performance. The influence of the aggregation state of CdSe QDs on the NDR performance is also studied, which indicates that the NDR is caused by the resonant tunneling process in the ITO/CdSe QD/organic active layer structure.展开更多
We investigate the electronic transport properties of atomic carbon chain-graphene junctions by using the density-functionla theory combining with the non-equilibrium Green＇s functions. The results show that the tran...We investigate the electronic transport properties of atomic carbon chain-graphene junctions by using the density-functionla theory combining with the non-equilibrium Green＇s functions. The results show that the transport properties are sensitively dependent on the contact geometry of carbon chain. From the calculated I-V curve we find negative differential resistance （NDR） in the two types of junctions. The NDR can be considered as a result of molecular orbitals moving related to the bias window.展开更多
The electronic and transport characteristics of protonated derivatives of naphthalocyanine(Nc)were investigated using density functional theory and non-equilibrium Green's functions.The results indicate that the p...The electronic and transport characteristics of protonated derivatives of naphthalocyanine(Nc)were investigated using density functional theory and non-equilibrium Green's functions.The results indicate that the protonation of external meso-N atoms of Nc preserves its planar structure and is energetically more favorable than the protonation of internal isoindole-N atoms.The protonation shifts the energy levels of system's frontier molecular orbitals closer to the Fermi level,thus creating channels for electron transport.In contrast with the semiconductor transport properties of H2Nc,its protonation products respond more sensitively to bias and exhibit negative differential resistance phenomena at specific bias.展开更多
We report the experimental phenomenon of large resistance change in plasma oxidized TiOx/TiNx film fabricated on W bottom-electrode-contact （W-BEC） array. The W-BEC in diameter 26Ohm is fabricated by a 0.18μm CMOS ...We report the experimental phenomenon of large resistance change in plasma oxidized TiOx/TiNx film fabricated on W bottom-electrode-contact （W-BEC） array. The W-BEC in diameter 26Ohm is fabricated by a 0.18μm CMOS technology, and the TiOx/TiNx cell array is formed by rf magnetron sputtering and reactive ion etching. In current-voltage （I- V） measurement for current-sweeping mode, large snap-back of voltage is observed, which indicates that the sample changes from high-resistance state （HRS） to low-resistance state （LRS）. In the I-V measurement for voltage-sweeping mode, large current collapse is observed, which indicates that the sample changes from LRS to HRS. The current difference between HRS and LRS is about two orders. The threshold current and voltage for the resistance change is about 5.0- 10^-5 A and 2.5 V, respectively. The pulse voltage can also change the resistance and the pulse time is as shorter as 30 ns for the resistance change. These properties of TiOx/TiNx film are comparable to that of conventional phase-change material, which makes it possible for RRAM application.展开更多
The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag...The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.展开更多
Based on the region model of lambda bipolar transistor ( LBT), a dividing region theory model of PLBT is set up,simulated and verified. Firstly, the principal operations of different kinds of photoelectronic lambda bi...Based on the region model of lambda bipolar transistor ( LBT), a dividing region theory model of PLBT is set up,simulated and verified. Firstly, the principal operations of different kinds of photoelectronic lambda bipolar transistor ( PLBT) are characterized by a simple circuit model. Through mathematical analysis of the equivalent circuit, the typical characteristics curve is divided into positive resistance, peak, negative resistance and cutoff regions. Secondly, by analyzing and simulating this model, the ratio of MOSFET width to channel length, threshold voltage and common emitter gain are discovered as the main structure parameters that determine the characteristic curves of PLBT. And peak region width, peak current value, negative resistance value and valley voltage value of PLBT can be changed conveniently according to the actual demands by modifying these parameters. Finally comparisons of the characteristics of the fabricated devices and the simu- lation results are made, which show that the analytical results are in agreement with the observed devices characteristics.展开更多
The fabrication process of Cu/Al2O3/MgF2/Au double-barrier metal/insulator/metal junction （DMIMJ） was introduced, and more stable light emission from this junction was successfully observed. The light emission physi...The fabrication process of Cu/Al2O3/MgF2/Au double-barrier metal/insulator/metal junction （DMIMJ） was introduced, and more stable light emission from this junction was successfully observed. The light emission physical mechanism of the junction was discussed. Results show that light emission spectrum of this structure locates at wavelength of 250-700 nm with two peaks at around 460 nm and 640 nm, which moves towards shorter wavelength region in comparison with that of the Al/Al2O3/Au junction. The light emission efficiency of this junction ranges from 0.7×10^-5-2.0×10^-5, which is 1 to 2 orders higher than that of the single-barrier Al/Al2O3/Au junction. The improved properties of this structure should be due to the electrons resonant tunneling effect in the double-barrier.展开更多
The MOBILE is a logic element realizing the monostable-bistable transition of a circuit that consists of two resonant tunneling transistors—the resonant tunneling diodes (RTDs) connected in series. It has several adv...The MOBILE is a logic element realizing the monostable-bistable transition of a circuit that consists of two resonant tunneling transistors—the resonant tunneling diodes (RTDs) connected in series. It has several advantages including multiple inputs and multiple functions. In this paper, by connecting a heterojunction phototransistor (HPT) with the MOBILE, a novel optoelectronic functional device can be got, which presents the function of both photocurrent switching and photocurrent latching. These behaviors have been demonstrated for the first time by simulating experiments and circuit simulations, with RTDs firstly manufactured in China. Research indicates that the novel photo-controlled MOBILE has the same logic functions as conventional electrical MOBILE except for with light as an input signal.展开更多
文摘This paper presents a novel scheme for enhancing resistance that utilizes an equivalent negative resistance. Adopting this novel scheme in the proposed current source could remarkably boost its output resistance without requiring increased power supply. Simulation with 0.6μm CMOS process models shows that the output resistance of the novel current source can reach the order of 10^9Ω with a 1.04GHz bandwidth and only 10.6ppm/℃ in the range of -40～145℃.
文摘A low-voltage, low-power, and high-gain rail-to-rail operational amplifier （OpAmp） is presented. The replica-amplifier gain enhancement technique is applied to improve the DC gain of the amplifier, which does not degrade the output swing and is very suitable for low-voltage applications. In a 0. 18/μm standard CMOS process,a 1V OpAmp with rail-to-rail output is designed. For a load capacitance of 5 pF,simulation by HSPICE shows that this OpAmp achieves an effective open-loop DC gain of 65. 9dB,gain bandwidth of 70.28 MHz,and phase margin of 50 with a quiescent power dissipation of 156.7μW.
基金National Natural Science Foundation of China (No 59975068) Natural Science Foundation of Tianjin (No993602911)
文摘A mathematical model is established on the basis of the physical characteristic of the negative resistance arc when a low current of 0—50 A is applied in pulsed TIG welding. The simulation model converted from the mathematical model is run in MATLAB environment, and the discussion is focused on the way the peak current ranging from 29 A to 50 A and the time constant of arc in the span of 0.003—0.006 s influence the simulating results and the dynamic characteristic. The simulating data are close to that of welding experiments and correspond to the theoretical conclusion.
文摘It is a common misconception that electric “resistance” always is a positive defined electric element. <em>i.e.</em>, the plot of the voltage across the resistor, V vs. its current, i is a slanted straight line with a positive slope. Esaki diode also known as tunnel diode is an exception to this character. For a certain voltage range, the current recedes resulting in a line with a negative slope;it is interpreted as negative resistance. In this research flavored report, we investigate the impact of the negative resistance in a typical classic electric circuit. E.g., a tunnel diode, D is inserted in a classic electric circuit that is composed of an ohmic resistor, R and a capacitor, C which are all in series with a DC power supply. The circuit equation for the RCD circuit is a nonlinear ordinary differential equation (NLODE). In line with the ever-growing popular Computer Algebra System (CAS), this is solved numerically utilizing two distinctly different CASs. The consistency of the solutions confidently leads to the understanding of the impact of the negative resistance. The circuit characteristics are compared to the classic analogous RC circuit. The report embodies an atlas of characteristics of the circuits making the analysis visually comprehensible.
文摘The I-V diagram of a tunnel diode inherits a voltage range corresponding to a specific current domain with a negative slope. Within this range, the electric resistance is negatively impacting the characteristics of the electric circuits. One such circuit containing a tunnel diode in series with an inductor driven by a DC source is considered. The negative resistance significantly alters the characteristics of the circuit. In this research-oriented project, we unveil these characteristics comparing them to the classic inductive circuit with an ohmic resistor. This project stems from our previous work [1] and may be considered an application of the tunnel diode embodying unseen surprises. The circuit analysis is entirely based on utilizing a Computer Algebra System (CAS) specifically Mathematica. Without a CAS, the completion of the project wouldn’t have been possible otherwise.
基金support from the National Natural Science Foundation of China(Nos.11604173,61625404,61888102,and 51973100)the China Postdoctoral Science Foundation(No.2017M612195)+1 种基金State Key Laboratory of Bio-Fibers and Eco-Textiles,Qingdao University(No.RZ2000003334)fund from the National Key Research Development Project(No.2019YFC0121402).
文摘The weft-knitted reduced graphene oxide(r-GO)textile that is made up of many conductive r-GO coated fibers was successfully prepared dependent on the electrospray deposition technique.Interestingly,the r-GO textile presents negative resistance variation not only in axial direction as the pressure increases but also in transverse direction as the lateral stretch increases which makes it has the advantage to fabricate the reliable sensors based on strain-resistance effect.The transverse-strain and pressure sensors based on the r-GO textiles all show the excellent sensing characteristics such as high sensitivity,reliability,and good durability,etc.The maximum gauge factors(GF)of the transverse-sensor are 27.1 and 153.5 in the x-and/-direction,respectively.And the practical detection range can up to 40%in the x-direction and 35%in the y-direction,respectively.The r-GO textile pressure sensor also shows high sensitivity for a broad pressure range that with a GF up to 716.8 kPa-1 for less than 4.5 kPa region and still has more sensitive pressure sensing characteristics even the pressure goes up to 14 kPa.Based on those good performances of r-GO textile sensors,its potential applications in human body states monitoring have been studied.
文摘We obtained the output characteristics in wurtzite Al0.15Ga0.85N/GaN MODFETs with the full band Monte Carlo method. The gate length Lg and the channel length Los in the device are 0.2 μm and 0.4 urn, respectively. In the output characteristics we found a differential negative resistance effect. That is, as VDS is a constant, initially, VDS increases with increasing VDS. When VDS exceeds a certain critical value, IDS decreases with increasing VDS. The analysis for velocity-field characteristics in wurtzite CaN, the distributions of the electric field and the electron velocity in the two dimensional electron gas channel indicates that the differential negative resistance effect of the electron average velocity results in the differential negative resistance effect of the output characteristics. The transient transport also is related to the differential negative resistance effect of the output characteristics. This effect only can be observed in the devices with very short channel.
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.11174214 and No.11204192）, the Research Project of Education Department in Sichuan Province （No.13ZB0207）, and Scientific Research Project of Yibin University （No.2013YY05）.
文摘The electron transport of linear atomic chain trodes was investigated by using the density Green＇s function method. We have calculated of MgB2 sandwiched between Au（100） elecfunctional theory with the non-equilibrium the corresponding cohesion energy and conductance of junctions in different distance. It is found that, at the equilibrium position, the Au-B bond-length is 1.90 A, the B-Mg bond-length is 2.22 A, and the equilibrium conductance is 0.51G0 （Go=2e^2/h）. The transport channel is almost formed by the π antibonding orbitals, which was made up of the Px and Py orbital electrons of B and Mg atoms. In the voltage range of -1.5 to 1.5 V, the junctions show the metallic behaviors. When the voltage is larger than 1.5 V, the current decreases gradually and then negative differential resistance appears almost symmetrically on both positive and negative bias.
基金This work was partially supported by the National Natural Science Foundation of China （No.20903003 and No.21273208）, the Anhui Provincial Natural Science Foundation （No.1408085QB26）, the China Postdoctoral Science Foundation （No.2012M511409）, the Supercomputer Center of Chinese Academy of Sciences, and University of Science and Technology of China and Shanghai Supercomputer Centers.
文摘We explore the electronic and transport properties of zigzag graphene nanoribbons （GNRs） with nitrogen-vacancy defects by performing fully self-consistent spin-polarized density functional theory calculations combined with non-equilibrium Green＇s function technique. We observe robust negative di erential resistance （NDR） effect in all examined molecular junctions. Through analyzing the calculated electronic structures and the bias-dependent transmission coefficients, we find that the narrow density of states of electrodes and the bias-dependent effective coupling between the central molecular orbitals and the electrode subbands are responsible for the observed NDR phenomenon. In addition, the obvious di erence of the transmission spectra of two spin channels is observed in some bias ranges, which leads to the near perfect spin-filtering effect. These theoretical findings imply that GNRs with nitrogenvacancy defects hold great potential for building molecular devices.
基金supported by the National Natural Science Foundation of China (Grant Nos.10325415 and 50504017)the Natural Science Foundation of Hunan Province,China (Grant No.07JJ3102)the Science Develop Foundation of Central South University,China (Grant Nos.08SDF02 and 09SDF09)
文摘By using first-principles calculations and nonequilibrium Green＇s function technique, we study elastic transport properties of crossed graphene nanoribbons. The results show that the electronic transport properties of molecular junctions can be modulated by doped atoms. Negative differential resistance （NDR） behaviour can be observed in a certain bias region, when crossed graphene nanoribbons are doped with nitrogen atoms at the shoulder, but it cannot be observed for pristine crossed graphene nanoribbons at low biases. A mechanism for the negative differential resistance behaviour is suggested.
基金sponsored by the National Key Research and Development Program of China(Nos.2017YFA0206202 and 2022YFA1203904)the National Natural Science Foundation of China(No.52271160).
文摘Owing to rapid developments in spintronics,spin-based logic devices have emerged as promising tools for next-generation computing technologies.This paper provides a comprehensive review of recent advancements in spin logic devices,particularly focusing on fundamental device concepts rooted in nanomagnets,magnetoresistive random access memory,spin–orbit torques,electric-field modu-lation,and magnetic domain walls.The operation principles of these devices are comprehensively analyzed,and recent progress in spin logic devices based on negative differential resistance-enhanced anomalous Hall effect is summarized.These devices exhibit reconfigur-able logic capabilities and integrate nonvolatile data storage and computing functionalities.For current-driven spin logic devices,negative differential resistance elements are employed to nonlinearly enhance anomalous Hall effect signals from magnetic bits,enabling reconfig-urable Boolean logic operations.Besides,voltage-driven spin logic devices employ another type of negative differential resistance ele-ment to achieve logic functionalities with excellent cascading ability.By cascading several elementary logic gates,the logic circuit of a full adder can be obtained,and the potential of voltage-driven spin logic devices for implementing complex logic functions can be veri-fied.This review contributes to the understanding of the evolving landscape of spin logic devices and underscores the promising pro-spects they offer for the future of emerging computing schemes.
基金Project(50721003)supported by the National Natural Science Foundation of ChinaProject(10C1171)supported by the Scientific Research Fund of Hunan Provincial Education Department,ChinaProject(11JJ3073)supported by the Natural Science Foundation of Hunan Province,China
文摘By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the electronic transport properties of molecular devices are affected by doped atoms. Negative differential resistance (NDR) behavior can be observed in certain bias regions for C82 and C80BN molecular devices but cannot be observed for C80N2 molecular device. A mechanism for the negative differential resistance behavior was suggested.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61106123 and 61275034the National Basic Research Program of China under Grant No 2013CB328705
文摘Room-temperature negative differential resistance （NDR） has been observed in different types of organic materials. However, detailed study on the influence of the organic material on NDR performance is still scarce. In this work, room-temperature NDR ＆ observed when CdSe quantum dot （QD） modified ITO is used as the electrode. Furthermore, material dependence of the NDR performance is observed by selecting materials with different charge transporting properties as the active layer, respectively. A peak-to-valley current ratio up to 9 is observed. It is demonstrated that the injection barrier between ITO and the organic active layer plays a decisive role for the device NDR performance. The influence of the aggregation state of CdSe QDs on the NDR performance is also studied, which indicates that the NDR is caused by the resonant tunneling process in the ITO/CdSe QD/organic active layer structure.
基金Supported by the National Natural Science Foundation of China under Grant No. 10832005the Program for Changjiang Scholars and Innovative Research Team in University under Grant No. IRT0730Program for International S&T Cooperation Program of China under Grant No. 2009DFA02320
文摘We investigate the electronic transport properties of atomic carbon chain-graphene junctions by using the density-functionla theory combining with the non-equilibrium Green＇s functions. The results show that the transport properties are sensitively dependent on the contact geometry of carbon chain. From the calculated I-V curve we find negative differential resistance （NDR） in the two types of junctions. The NDR can be considered as a result of molecular orbitals moving related to the bias window.
基金supported by the Postgraduate Inovation Programme of Changchun Wormal University(YJSCX202424)the Science and Technology Project of Jilin Provincial Education Department(JJKH20220828KJ)the Natural Science Foundation of Changchun Normal University(2020-005).
文摘The electronic and transport characteristics of protonated derivatives of naphthalocyanine(Nc)were investigated using density functional theory and non-equilibrium Green's functions.The results indicate that the protonation of external meso-N atoms of Nc preserves its planar structure and is energetically more favorable than the protonation of internal isoindole-N atoms.The protonation shifts the energy levels of system's frontier molecular orbitals closer to the Fermi level,thus creating channels for electron transport.In contrast with the semiconductor transport properties of H2Nc,its protonation products respond more sensitively to bias and exhibit negative differential resistance phenomena at specific bias.
基金Supported by the National Basic Research Program of China under Grant No 2006CB302700, the National High Technology Development Programme of China under Grant No 2006AA03Z360~ Chinese Academy of Sciences （Y2005027）, Science and Technology Council of Shanghai under Grant Nos AM0517, 05JC14076, 0552nm043, 06QA14060, 06XD14025, 0652nm003, and 06DZ22017, the China Postdoctoral Science Foundation, and the K. C. Wong Education Foundation （Hong Kong）.
文摘We report the experimental phenomenon of large resistance change in plasma oxidized TiOx/TiNx film fabricated on W bottom-electrode-contact （W-BEC） array. The W-BEC in diameter 26Ohm is fabricated by a 0.18μm CMOS technology, and the TiOx/TiNx cell array is formed by rf magnetron sputtering and reactive ion etching. In current-voltage （I- V） measurement for current-sweeping mode, large snap-back of voltage is observed, which indicates that the sample changes from high-resistance state （HRS） to low-resistance state （LRS）. In the I-V measurement for voltage-sweeping mode, large current collapse is observed, which indicates that the sample changes from LRS to HRS. The current difference between HRS and LRS is about two orders. The threshold current and voltage for the resistance change is about 5.0- 10^-5 A and 2.5 V, respectively. The pulse voltage can also change the resistance and the pulse time is as shorter as 30 ns for the resistance change. These properties of TiOx/TiNx film are comparable to that of conventional phase-change material, which makes it possible for RRAM application.
基金the National Natural Science FOundation of China under grant! No.19974041the National Major Fundamental ResearCh Program-Nal
文摘The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.
基金Supported by "973" National Key Basic Research Program ( No. 2002CB311905).
文摘Based on the region model of lambda bipolar transistor ( LBT), a dividing region theory model of PLBT is set up,simulated and verified. Firstly, the principal operations of different kinds of photoelectronic lambda bipolar transistor ( PLBT) are characterized by a simple circuit model. Through mathematical analysis of the equivalent circuit, the typical characteristics curve is divided into positive resistance, peak, negative resistance and cutoff regions. Secondly, by analyzing and simulating this model, the ratio of MOSFET width to channel length, threshold voltage and common emitter gain are discovered as the main structure parameters that determine the characteristic curves of PLBT. And peak region width, peak current value, negative resistance value and valley voltage value of PLBT can be changed conveniently according to the actual demands by modifying these parameters. Finally comparisons of the characteristics of the fabricated devices and the simu- lation results are made, which show that the analytical results are in agreement with the observed devices characteristics.
基金Funded by the National Natural Science Foundation of China (No.69576006)
文摘The fabrication process of Cu/Al2O3/MgF2/Au double-barrier metal/insulator/metal junction （DMIMJ） was introduced, and more stable light emission from this junction was successfully observed. The light emission physical mechanism of the junction was discussed. Results show that light emission spectrum of this structure locates at wavelength of 250-700 nm with two peaks at around 460 nm and 640 nm, which moves towards shorter wavelength region in comparison with that of the Al/Al2O3/Au junction. The light emission efficiency of this junction ranges from 0.7×10^-5-2.0×10^-5, which is 1 to 2 orders higher than that of the single-barrier Al/Al2O3/Au junction. The improved properties of this structure should be due to the electrons resonant tunneling effect in the double-barrier.
文摘The MOBILE is a logic element realizing the monostable-bistable transition of a circuit that consists of two resonant tunneling transistors—the resonant tunneling diodes (RTDs) connected in series. It has several advantages including multiple inputs and multiple functions. In this paper, by connecting a heterojunction phototransistor (HPT) with the MOBILE, a novel optoelectronic functional device can be got, which presents the function of both photocurrent switching and photocurrent latching. These behaviors have been demonstrated for the first time by simulating experiments and circuit simulations, with RTDs firstly manufactured in China. Research indicates that the novel photo-controlled MOBILE has the same logic functions as conventional electrical MOBILE except for with light as an input signal.
