The idea of stacking multiple monolayers of different two-dimensional materials has become a global pursuit. In this work a silicene armchair nanoribbon of width W and van der Waals-bonded to different transition-meta...The idea of stacking multiple monolayers of different two-dimensional materials has become a global pursuit. In this work a silicene armchair nanoribbon of width W and van der Waals-bonded to different transition-metal dichalcogenide （TMD） bilayer substrates MoX2 and WX2, where X = S, Se, Te is considered. The orbital resolved electronic structure and ballistic transport properties of these systems are simulated by employing van der Waals-corrected density functional theory and nonequilibrium Green＇s functions. We find that the lattice mismatch with the underlying substrate determines the electronic structure, correlated with the silicene buckling distortion and ultimately with the contact resistance of the two-terminal system. The smallest lattice mismatch, obtained with the MoTe2 substrate, results in the silicene ribbon properties coming close to those of a freestanding one. With the TMD bilayer acting as a dielectric layer, the electronic structure is tunable from a direct to an indirect semiconducting layer, and subsequently to a metallic electronic dispersion layer, with a moderate applied perpendicular electric field.展开更多
Because of the coupling between semiconducting and piezoelectric properties in wurtzite materials, strain-induced piezo-charges can tune the charge transport across the interface or junction, which is referred to as t...Because of the coupling between semiconducting and piezoelectric properties in wurtzite materials, strain-induced piezo-charges can tune the charge transport across the interface or junction, which is referred to as the piezotronic effect. For devices whose dimension is much smaller than the mean free path of carriers （such as a single atomic layer of MoS2）, ballistic transport occurs. In this study, transport in the monolayer MoS2 piezotronic transistor is studied by presenting analytical solutions for two-dimensional （2D） MoS2. Furthermore, a numerical simulation for guiding future 2D piezotronic nanodevice design is presented.展开更多
We report on a theoretical investigation of a direct current generation in carbon nanotubes (CNTs) that are stimulated axially by terahertz (THz) field. We consider the kinetic approach based on the semiclassical Bolt...We report on a theoretical investigation of a direct current generation in carbon nanotubes (CNTs) that are stimulated axially by terahertz (THz) field. We consider the kinetic approach based on the semiclassical Boltzmann’s transport equation with constant relaxation time approximation, together with the energy spectrum of an electron in the tight-binding approximation. Our results indicate that for strong THz-fields, there is simultaneous generation of DC current in the axial and circumferential directions of the CNTs, even at room temperature. We found that a THz-field can induce a negative conductivity in the CNTs that leads to the THz field induced DC current. For varying amplitude of the THz-field, the current density decreases rapidly and modulates around zero with interval of negative conductivity. The interval decreases with increasing the amplitude of the THz-field. We show that the THz-field can cause fast switching from a zero DC current to a finite DC current due to the quasi-ballistic transport, and that electron scattering is a necessary condition for switching.展开更多
Apart from usual quantization steps on the ballistic conductance of quasi-one-dimensional conductor, an additional plateau-like feature appears at a fraction of about 0.7 below the first conductance step in GaAs-based...Apart from usual quantization steps on the ballistic conductance of quasi-one-dimensional conductor, an additional plateau-like feature appears at a fraction of about 0.7 below the first conductance step in GaAs-based quantum point contacts (QPCs). Despite a tremendous amount of research on this anomalous feature, its origin remains still unclear. Here, a unique model of this anomaly is proposed relying on fundamental principles of quantum mechanics. It is noticed that just after opening a quasi-1D conducting channel in the QPC a single electron travels the channel at a time, and such electron can be—in principle—observed. The act of observation destroys superposition of spin states, in which the electron otherwise exists, and this suppresses their quantum interference. It is shown that then the QPC-conductance is reduced by a factor of 0.74. “Visibility” of electron is enhanced if the electron spends some time in the channel due to resonant transmission. Electron’s resonance can also explain an unusual temperature behavior of the anomaly as well as its recently discovered feature: oscillatory modulation as a function of the channel length and electrostatic potential. A recipe for experimental verification of the model is given.展开更多
Using the Monte Carlo method,a type of semiconductor nano-device called self-switching device (SSD),which has diode-like I-V characteristics,was simulated.After analyzing the microscopic transport behavior of the carr...Using the Monte Carlo method,a type of semiconductor nano-device called self-switching device (SSD),which has diode-like I-V characteristics,was simulated.After analyzing the microscopic transport behavior of the carriers,we show that the ballistic effects exist in the SSDs when the channel length of the device is extremely short (～120 nm).Furthermore,we show that the ballistic effect doubles the average drift velocity of the carriers (to ～6.0×107 cm/s) in short-channel SSDs,which decreases the transit time.This implies that when the dimensions are decreased to nanoscale length,the SSD can operate much faster because the ballistic effect increases the operation speed of the device.Moreover,because of the ballistic transport,the energy efficiency may also be improved.展开更多
Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Som...Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Some resonant transmission peaks and stop-frequency gaps can be observed,and the number and positions of these peaks and gaps are sensitive to the sizes of DQDs.With increasing the temperature,the thermal conductance undergoes a transition from the decrease to increase,and can be efficiently tuned by modulating the radius,length of DQDs as well as the interval between DQDs.In addition,at low temperatures,the enhancement of the thermal conductance can be also observed in this case.Some similarities and differences between the cylindrical and rectangular structures are identified.展开更多
This work reviews the state-of-the art multi-gate field-effect transistor(MuGFET)process technologies and compares the device performance and reliability characteristics of the MuGFETs with the planar Si CMOS devices....This work reviews the state-of-the art multi-gate field-effect transistor(MuGFET)process technologies and compares the device performance and reliability characteristics of the MuGFETs with the planar Si CMOS devices.Owing to the 3D wrapped gate structure,MuGFETs can suppress the SCEs and improve the ON-current performance due to the volume inversion of the channel region.As the Si CMOS technology pioneers to sub-10 nm nodes,the process challenges in terms of lithography capability,process integration controversies,performance variability etc.were also discussed in this work.Due to the severe self-heating effect in the MuGFETs,the ballistic transport and reliability characteristics were investigated.Future alternatives for the current Si MuGFET technology were discussed at the end of the paper.More work needs to be done to realize novel high mobility channel MuGFETs with better performance and reliability.展开更多
文摘The idea of stacking multiple monolayers of different two-dimensional materials has become a global pursuit. In this work a silicene armchair nanoribbon of width W and van der Waals-bonded to different transition-metal dichalcogenide （TMD） bilayer substrates MoX2 and WX2, where X = S, Se, Te is considered. The orbital resolved electronic structure and ballistic transport properties of these systems are simulated by employing van der Waals-corrected density functional theory and nonequilibrium Green＇s functions. We find that the lattice mismatch with the underlying substrate determines the electronic structure, correlated with the silicene buckling distortion and ultimately with the contact resistance of the two-terminal system. The smallest lattice mismatch, obtained with the MoTe2 substrate, results in the silicene ribbon properties coming close to those of a freestanding one. With the TMD bilayer acting as a dielectric layer, the electronic structure is tunable from a direct to an indirect semiconducting layer, and subsequently to a metallic electronic dispersion layer, with a moderate applied perpendicular electric field.
基金This work was supported by the ＂thousands talents＂ program for pioneer researcher and his innovation team, China, the National Natural Science Foundation of China （No. 51432005）, and Beijing Municipal Commission of Science and Technology （Nos. Z131100006013005 and Z131100006013004）.
文摘Because of the coupling between semiconducting and piezoelectric properties in wurtzite materials, strain-induced piezo-charges can tune the charge transport across the interface or junction, which is referred to as the piezotronic effect. For devices whose dimension is much smaller than the mean free path of carriers （such as a single atomic layer of MoS2）, ballistic transport occurs. In this study, transport in the monolayer MoS2 piezotronic transistor is studied by presenting analytical solutions for two-dimensional （2D） MoS2. Furthermore, a numerical simulation for guiding future 2D piezotronic nanodevice design is presented.
文摘We report on a theoretical investigation of a direct current generation in carbon nanotubes (CNTs) that are stimulated axially by terahertz (THz) field. We consider the kinetic approach based on the semiclassical Boltzmann’s transport equation with constant relaxation time approximation, together with the energy spectrum of an electron in the tight-binding approximation. Our results indicate that for strong THz-fields, there is simultaneous generation of DC current in the axial and circumferential directions of the CNTs, even at room temperature. We found that a THz-field can induce a negative conductivity in the CNTs that leads to the THz field induced DC current. For varying amplitude of the THz-field, the current density decreases rapidly and modulates around zero with interval of negative conductivity. The interval decreases with increasing the amplitude of the THz-field. We show that the THz-field can cause fast switching from a zero DC current to a finite DC current due to the quasi-ballistic transport, and that electron scattering is a necessary condition for switching.
文摘Apart from usual quantization steps on the ballistic conductance of quasi-one-dimensional conductor, an additional plateau-like feature appears at a fraction of about 0.7 below the first conductance step in GaAs-based quantum point contacts (QPCs). Despite a tremendous amount of research on this anomalous feature, its origin remains still unclear. Here, a unique model of this anomaly is proposed relying on fundamental principles of quantum mechanics. It is noticed that just after opening a quasi-1D conducting channel in the QPC a single electron travels the channel at a time, and such electron can be—in principle—observed. The act of observation destroys superposition of spin states, in which the electron otherwise exists, and this suppresses their quantum interference. It is shown that then the QPC-conductance is reduced by a factor of 0.74. “Visibility” of electron is enhanced if the electron spends some time in the channel due to resonant transmission. Electron’s resonance can also explain an unusual temperature behavior of the anomaly as well as its recently discovered feature: oscillatory modulation as a function of the channel length and electrostatic potential. A recipe for experimental verification of the model is given.
基金supported by the FOK YING TONG Education Foundation (122004)the Natural Science Foundation of Guangdong Province,China (9451063101002244,10151063101000025)
文摘Using the Monte Carlo method,a type of semiconductor nano-device called self-switching device (SSD),which has diode-like I-V characteristics,was simulated.After analyzing the microscopic transport behavior of the carriers,we show that the ballistic effects exist in the SSDs when the channel length of the device is extremely short (～120 nm).Furthermore,we show that the ballistic effect doubles the average drift velocity of the carriers (to ～6.0×107 cm/s) in short-channel SSDs,which decreases the transit time.This implies that when the dimensions are decreased to nanoscale length,the SSD can operate much faster because the ballistic effect increases the operation speed of the device.Moreover,because of the ballistic transport,the energy efficiency may also be improved.
基金supported by the National Natural Science Foundation of China (Grant No.11204074)
文摘Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots(DQDs) are investigated.Results show that the transmission coefficients exhibit the irregular oscillation.Some resonant transmission peaks and stop-frequency gaps can be observed,and the number and positions of these peaks and gaps are sensitive to the sizes of DQDs.With increasing the temperature,the thermal conductance undergoes a transition from the decrease to increase,and can be efficiently tuned by modulating the radius,length of DQDs as well as the interval between DQDs.In addition,at low temperatures,the enhancement of the thermal conductance can be also observed in this case.Some similarities and differences between the cylindrical and rectangular structures are identified.
基金This work was supported by Zhejiang Provincial Natural Science Foundation of China under Grant LR18F040001,LY19F040001the Opening Project of Key Laboratory of Microelectronic Devices&Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences.
文摘This work reviews the state-of-the art multi-gate field-effect transistor(MuGFET)process technologies and compares the device performance and reliability characteristics of the MuGFETs with the planar Si CMOS devices.Owing to the 3D wrapped gate structure,MuGFETs can suppress the SCEs and improve the ON-current performance due to the volume inversion of the channel region.As the Si CMOS technology pioneers to sub-10 nm nodes,the process challenges in terms of lithography capability,process integration controversies,performance variability etc.were also discussed in this work.Due to the severe self-heating effect in the MuGFETs,the ballistic transport and reliability characteristics were investigated.Future alternatives for the current Si MuGFET technology were discussed at the end of the paper.More work needs to be done to realize novel high mobility channel MuGFETs with better performance and reliability.
