Poly(methyl methacrylate)(PMMA) is widely used for graphene transfer and device fabrication.However,it inevitably leaves a thin layer of polymer residues after acetone rinsing and leads to dramatic degradation of devi...Poly(methyl methacrylate)(PMMA) is widely used for graphene transfer and device fabrication.However,it inevitably leaves a thin layer of polymer residues after acetone rinsing and leads to dramatic degradation of device performance.How to eliminate contamination and restore clean surfaces of graphene is still highly demanded.In this paper,we present a reliable and position-controllable method to remove the polymer residues on graphene films by laser exposure.Under proper laser conditions,PMMA residues can be substantially reduced without introducing defects to the underlying graphene.Furthermore,by applying this laser cleaning technique to the channel and contacts of graphene fieldeffect transistors(GFETs),higher carrier mobility as well as lower contact resistance can be realized.This work opens a way for probing intrinsic properties of contaminant-free graphene and fabricating high-performance GFETs with both clean channel and intimate graphene/metal contact.展开更多
A low-noise readout integrated circuit for high-energy particle detector is presented.The noise of charge sensitive amplifier was suppressed by using single-side amplifier and resistors as source degeneration.Continuo...A low-noise readout integrated circuit for high-energy particle detector is presented.The noise of charge sensitive amplifier was suppressed by using single-side amplifier and resistors as source degeneration.Continuous-time semi-Gaussian filter is chosen to avoid switch noise.The peaking time of pulse shaper and the gain can be programmed to satisfy multi-application.The readout integrated circuit has been designed and fabricated using a 0.35 μm double-poly triple-metal CMOS technology.Test results show the functions of the readout integrated circuit are correct.The equivalent noise charge with no detector connected is 500–700 e in the typical mode,the gain is tunable within 13–130 mV/fC and the peaking time varies from 0.7 to 1.6 μs,in which the average gain is about 20.5 mV/fC,and the linearity reaches 99.2%.展开更多
The comprehensive understanding of the structure-dependent electrostatic discharge behaviors in a conventional diode-triggered silicon controlled rectifier （DTSCR） is presented in this paper. Combined with the devic...The comprehensive understanding of the structure-dependent electrostatic discharge behaviors in a conventional diode-triggered silicon controlled rectifier （DTSCR） is presented in this paper. Combined with the device simulation, a mathematical model is built to get a more in-depth insight into this phenomenon. The theoretical studies are verified by the transmission-line-pulsing （TLP） test results of the modified DTSCR structure, which is realized in a 65-nm complementary metal-oxide-semiconductor （CMOS） process. The detailed analysis of the physical mechanism is used to provide predictions as the DTSCR-based protection scheme is required. In addition, a method is also presented to achieve the tradeoff between the leakage and trigger voltage in DTSCR.展开更多
Nitrogen plasma passivation （NPP） on （111） germanium （Ge） was studied in terms of the interface trap density, roughness, and interfacial layer thickness using plasma-enhanced chemical vapor deposition （PECVD）....Nitrogen plasma passivation （NPP） on （111） germanium （Ge） was studied in terms of the interface trap density, roughness, and interfacial layer thickness using plasma-enhanced chemical vapor deposition （PECVD）. The results show that NPP not only reduces the interface states, but also improves the surface roughness of Ge, which is beneficial for suppressing the channel scattering at both low and high field regions of Ge MOSFETs. However, the interracial layer thickness is also increased by the NPP treatment, which will impact the equivalent oxide thickness （EOT） scaling and thus degrade the device performance gain from the improvement of the surface morphology and the interface passivation. To obtain better device performance of Ge MOSFETs, suppressing the interfacial layer regrowth as well as a trade-off with reducing the interface states and roughness should be considered carefully when using the NPP process.展开更多
An extensive and complete experimental investigation with a full layout design of the channel direction was carried out for the first time to clarify the orientation dependence of germanium p-channel metal-oxide-semic...An extensive and complete experimental investigation with a full layout design of the channel direction was carried out for the first time to clarify the orientation dependence of germanium p-channel metal-oxide-semiconductor field-effect transistors （PMOSFETs）. By comparison of gate trans-conductance, drive current, and hole mobility, we found that the performance trend with the substrate orientation for Ge PMOSFET is （110）〉（111） ~ （100）, and the best channel direction is （110）/[110]. Moreover, the （110） device performance was found to be easily degraded as the channel direction got off from the [ 110] orientation, while （100） and （111） devices exhibited less channel orientation dependence. This experimental result shows good matching with the simulation reports to give a credible and significant guidance for Ge PMOSFET design.展开更多
In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si （110） nanowire via the simulation of strain distribution and the calculation of a genera...In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si （110） nanowire via the simulation of strain distribution and the calculation of a generalized 6 × 6k .p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO2 insulator, the strain of the HfO2 gate insulator in Si （110） nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design.展开更多
Memory cells have always been an important element of information technology.With emerging technologies like big data and cloud computing,the scale and complexity of data storage has reached an unprecedented peak with...Memory cells have always been an important element of information technology.With emerging technologies like big data and cloud computing,the scale and complexity of data storage has reached an unprecedented peak with a much higher requirement for memory technology.As is well known,better data storage is mostly achieved by miniaturization.However,as the size of the memory device is reduced,a series of problems,such as drain gate-induced leakage,greatly hinder the performance of memory units.To meet the increasing demands of information technology,novel and high-performance memory is urgently needed.Fortunately,emerging memory technologies are expected to improve memory performance and drive the information revolution.This review will focus on the progress of several emerging memory technologies,including two-dimensional material-based memories,resistance random access memory(RRAM),magnetic random access memory(MRAM),and phasechange random access memory(PCRAM).Advantages,mechanisms,and applications of these diverse memory technologies will be discussed in this review.展开更多
In this paper, oxidation of Ge surface by N2O plasma is presented and experimentally demonstrated. Results show that 1.0-nm GeO2 is achieved after 120-s N20 plasma oxidation at 300 ℃. The GeO2/Ge interface is atomica...In this paper, oxidation of Ge surface by N2O plasma is presented and experimentally demonstrated. Results show that 1.0-nm GeO2 is achieved after 120-s N20 plasma oxidation at 300 ℃. The GeO2/Ge interface is atomically smooth. The interface state density of Ge surface after N20 plasma passivation is about - 3 × 1011 cm-2.eV-1. With GeO2 passivation, the hysteresis of metal-oxide-semiconductor （MOS） capacitor with A1203 serving as gate dielectric is reduced to - 50 mV, compared with - 130 mV of the untreated one. The Fermi-level at GeO2/Ge interface is unpinned, and the surface potential is effectively modulated by the gate voltage.展开更多
The effects of the physical damages induced by heavy ion irradiation on the performance of partiallydepleted SOI devices are experimentally investigated. After heavy ion exposure, different degradation phenomena are o...The effects of the physical damages induced by heavy ion irradiation on the performance of partiallydepleted SOI devices are experimentally investigated. After heavy ion exposure, different degradation phenomena are observed due to the random strike of heavy ions. A decrease of the saturation current and transconductance,and an enhanced gate-induced drain leakage current are observed, which are mainly attributed to the displacement damages that may be located in the channel, the depletion region of the drain/body junction or the gate-to-drain overlap region. Further, PDSOI devices with and without body contact are compared, which reveals the differences in the threshold voltage shift, the drain-induced barrier lowing effect, the transconductance and the kink effect. The results may provide a guideline for radiation hardened design.展开更多
The dynamics of electron transport in single-layer MoS2 is simulated by employing the single particle Monte Carlo method. Acoustic phonon scattering, optical phonon scattering and Frohlich scattering are taken into ac...The dynamics of electron transport in single-layer MoS2 is simulated by employing the single particle Monte Carlo method. Acoustic phonon scattering, optical phonon scattering and Frohlich scattering are taken into account. It is found that the electron mobility decreases from 806cm2 /V.s for a transverse electrical field of 103 Vim to 426/112 cm2 /V.s for a transverse electrical field of 105/107 Vim. Further detailed analysis on carrier dynamics reveals that the low field mobility is dominated by the acoustic phonon scattering while the role of optical phonon scattering is to relax the electron energy below the optical phonon energy by efficient energy relaxation through optical phonon emission. Only when the transverse electrical field is larger than 106 V/m, the mobility can be determined by the optical phonon scattering, leading to a strong mobility degradation.展开更多
This paper studies an oxide/silicon core/shell nanowire MOSFET （OS-CSNM）. Through three-dimensional device simulations, we have demonstrated that the OS-CSNM has a lower leakage current and higher Ion/Ioff ratio aft...This paper studies an oxide/silicon core/shell nanowire MOSFET （OS-CSNM）. Through three-dimensional device simulations, we have demonstrated that the OS-CSNM has a lower leakage current and higher Ion/Ioff ratio after intro- ducing the oxide core into a traditional nanowire MOSFET （TNM）. The oxide/silicon OS-CSNM structure suppresses threshold voltage roll-off, drain induced barrier lowering and subthreshold swing degradation. Smaller intrinsic device delay is also observed in OS-CSNM in comparison with that of TNM.展开更多
Noble nanometals are of significance in both scientific interest and technological applications,which are usually obtained by conventional wet-chemical synthesis.Organic surfactants are always used in the synthesis to...Noble nanometals are of significance in both scientific interest and technological applications,which are usually obtained by conventional wet-chemical synthesis.Organic surfactants are always used in the synthesis to prevent unexpected overgrowth and aggregation of noble nanometals.However,the surfactants are hard to remove and may interfere with plasmonic and catalytic studies,remaining surfactant-free synthesis of noble nanometals a challenge.Herein,we report an approach to epitaxial growth of sizecontrolled noble nanometals on MXenes.As piloted by density functional theory calculations,along with work function experimental determination,kinetic and spectroscopic studies,epitaxial growth of noble nanometals is initiated via a mechanism that involves an in situ redox reaction.In the redox,MXenes as two-dimensional solid reductants whose work functions are compatible with the reduction potentials of noble metal cations,enable spontaneous donation of electrons from the MXenes to noble metal cations and reduce the cations into nanoscale metallic metals on the outmost surface of MXenes.Neither surfactants nor external reductants are used during the whole synthesis process,which addresses a long-standing interference issue of surfactant and external reductant in the conventional wet-chemical synthesis.Moreover,the MXenes induced noble nanometals are size-controlled.Impressively,noble nanometals firmly anchored on MXenes exhibit excellent performance towards surface enhanced Raman scattering.Our developed strategy will promote the nanostructure-controlled synthesis of noble nanometals,offering new opportunities to further improve advanced functional properties towards practical applications.展开更多
A novel voltage controlled oscillator （VCO） sub-band selection circuit to achieve fast phase locked loop （PLL） calibration is presented, which reduces the calibration time by measuring the period difference direct...A novel voltage controlled oscillator （VCO） sub-band selection circuit to achieve fast phase locked loop （PLL） calibration is presented, which reduces the calibration time by measuring the period difference directly and accomplishing an efficient search for an optimum VCO sub-band. The sub-band selection circuit was implemented in a 0.18 μm CMOS logic process with a PLL using an 8 sub-band VCO. The measured calibration time is less than 3 μs in a VCO frequency range from 600 MHz to 2 GHz. The proposed circuit consumes 0.64 mA at most.展开更多
The radiation response of 90 nm bulk silicon MOS devices after heavy ion irradiation is experimentally investigated. Due to the random strike of the incident particle, different degradation behaviors of bulk silicon M...The radiation response of 90 nm bulk silicon MOS devices after heavy ion irradiation is experimentally investigated. Due to the random strike of the incident particle, different degradation behaviors of bulk silicon MOS devices are observed. The drain current and maximum transconductance degrade as a result of the displacement damage in the channel induced by heavy ion strike. The off-state leakage current degradation and threshold voltage shift are also observed after heavy ion irradiation. The results suggest that the radiation induced damage of sub-100 nm MOS devices caused by heavy ion irradiation should be paid attention.展开更多
In the design of phase-change memory（PCM）,it is important to perform numerical simulations to predict the performances of different device structures.This work presents a numerical simulation using a coupled system ...In the design of phase-change memory（PCM）,it is important to perform numerical simulations to predict the performances of different device structures.This work presents a numerical simulation using a coupled system including Poisson＇s equation,the current continuity equation,the thermal conductivity equation,and phase-change dynamics to simulate the thermal and electric characteristics of phase-change memory.This method discriminates the common numerical simulation of PCM cells,from which it applies Possion＇s equation and current continuity equations instead of the Laplace equation to depict the electric characteristics of PCM cells,which is more adoptable for the semiconductor characteristics of phase-change materials.The results show that the simulation agrees with the measurement,and the scalability of PCM is predicted.展开更多
The impact of process induced variation on the response of SOI Fin FET to heavy ion irradiation is studied through 3-D TCAD simulation for the first time. When Fin FET biased at OFF state configuration（Vgs D0, Vds DV...The impact of process induced variation on the response of SOI Fin FET to heavy ion irradiation is studied through 3-D TCAD simulation for the first time. When Fin FET biased at OFF state configuration（Vgs D0, Vds DVdd/ is struck by a heavy ion, the drain collects ionizing charges under the electric field and a current pulse（single event transient, SET） is consequently formed. The results reveal that with the presence of line-edge roughness（LER）, which is one of the major variation sources in nano-scale Fin FETs, the device-to-device variation in terms of SET is observed. In this study, three types of LER are considered： type A has symmetric fin edges, type B has irrelevant fin edges and type C has parallel fin edges. The results show that type A devices have the largest SET variation while type C devices have the smallest variation. Further, the impact of the two main LER parameters,correlation length and root mean square amplitude, on SET variation is discussed as well. The results indicate that variation may be a concern in radiation effects with the down scaling of feature size.展开更多
Memristors proposed by Leon Chua provide a new type of memory device for novel neuromorphic computing applications.However,the approaching of distinct multi‐intermediate states for tunable switching dynamics,the con-...Memristors proposed by Leon Chua provide a new type of memory device for novel neuromorphic computing applications.However,the approaching of distinct multi‐intermediate states for tunable switching dynamics,the con-trolling of conducting filaments(CFs)toward high device repeatability and reproducibility,and the ability for large‐scale preparation devices,remain full of challenges.Here,we show that vertical‐organic‐nanocrystal‐arrays(VONAs)could make a way toward the challenges.The perfect one‐dimensional structure of the VONAs could confine the CFs accurately with fine‐tune resistance states in a broad range of 103 ratios.The availability of large‐area VONAs makes the fabrication of large‐area crossbar memristor arrays facilely,and the analog switching characteristic of the memristors is to effectively imitate different kinds of synaptic plasticity,indicating their great potential in future applications.展开更多
The diode-triggered silicon-controlled rectifier（DTSCR） is widely used for electrostatic discharge（ESD） protection in advanced CMOS process owing to its advantages, such as design simplification, adjustable trigge...The diode-triggered silicon-controlled rectifier（DTSCR） is widely used for electrostatic discharge（ESD） protection in advanced CMOS process owing to its advantages, such as design simplification, adjustable trigger/holding voltage, low parasitic capacitance. However, the multiple-triggering effect in the typical DTSCR device may cause undesirable larger overall trigger voltage, which results in a reduced ESD safe margin. In previous research, the major cause is attributed to the higher current level required in the intrinsic SCR. The related discussions indicate that it seems to result from the current division rule between the intrinsic and parasitic SCR formed in the triggering process. In this letter, inserting a large space into the trigger diodes is proposed to get a deeper insight into this issue. The triggering current is observed to be regularly reduced along with the increased space, which confirms that the current division is determined by the parasitic resistance distributed between the intrinsic and parasitic SCR paths. The theoretical analysis is well confirmed by device simulation and transmission line pulse（TLP） test results. The reduced overall trigger voltage is achieved in the modified DTSCR structures due to the comprehensive result of the parasitic resistance vs triggering current, which indicates a minimized multipletriggering effect.展开更多
Traditional feedforward structures suffer from performance constraints caused by the complex adder before quantizer.This paper presents an improved 4th-order 1 -bit sigma-delta modulator which has a simple adder and d...Traditional feedforward structures suffer from performance constraints caused by the complex adder before quantizer.This paper presents an improved 4th-order 1 -bit sigma-delta modulator which has a simple adder and delayed input feedforward to relax timing constraints and implement low-distortion.The modulator was fabricated in a 0.35μm CMOS process,and it achieved 92.8 dB SNDR and 101 dB DR with a signal bandwidth of 100 kHz dissipating 8.6 mW power from a 3.3-V supply.The performance satisfies the requirements of a GSM system.展开更多
This paper describes an 8-bit 125 MHz low-power CMOS fully-folding analog-to-digital converter （ADC） A novel mixed-averaging distributed T/H circuit is proposed to improve the accuracy. Folding circuits are not only...This paper describes an 8-bit 125 MHz low-power CMOS fully-folding analog-to-digital converter （ADC） A novel mixed-averaging distributed T/H circuit is proposed to improve the accuracy. Folding circuits are not only used in the fine converter but also in the coarse one and in the bit synchronization block to reduce the number of comparators for low power. This ADC is implemented in 0.5μm CMOS technology and occupies a die area of 2 × 1.5 mm^2. The measured differential nonlinearity and integral nonlinearity are 0.6 LSB/-0.8 LSB and 0.9 LSB/-1.2 LSB, respectively. The ADC exhibits 44.3 dB of signal-to-noise plus distortion ratio and 53.5 dB of spurious-free dynamic range for 1 MHz input sine-wave. The power dissipation is 138 mW at a sampling rate of 125 MHz at a 5 V supply.展开更多
基金the National Basic Research Program of China(Grant No.2013CBA01604)the National Science and Technology Major Project of China(Grant No.2011ZX02707)
文摘Poly(methyl methacrylate)(PMMA) is widely used for graphene transfer and device fabrication.However,it inevitably leaves a thin layer of polymer residues after acetone rinsing and leads to dramatic degradation of device performance.How to eliminate contamination and restore clean surfaces of graphene is still highly demanded.In this paper,we present a reliable and position-controllable method to remove the polymer residues on graphene films by laser exposure.Under proper laser conditions,PMMA residues can be substantially reduced without introducing defects to the underlying graphene.Furthermore,by applying this laser cleaning technique to the channel and contacts of graphene fieldeffect transistors(GFETs),higher carrier mobility as well as lower contact resistance can be realized.This work opens a way for probing intrinsic properties of contaminant-free graphene and fabricating high-performance GFETs with both clean channel and intimate graphene/metal contact.
基金Supported by the National Natural Science Foundation of China (No.40704025)
文摘A low-noise readout integrated circuit for high-energy particle detector is presented.The noise of charge sensitive amplifier was suppressed by using single-side amplifier and resistors as source degeneration.Continuous-time semi-Gaussian filter is chosen to avoid switch noise.The peaking time of pulse shaper and the gain can be programmed to satisfy multi-application.The readout integrated circuit has been designed and fabricated using a 0.35 μm double-poly triple-metal CMOS technology.Test results show the functions of the readout integrated circuit are correct.The equivalent noise charge with no detector connected is 500–700 e in the typical mode,the gain is tunable within 13–130 mV/fC and the peaking time varies from 0.7 to 1.6 μs,in which the average gain is about 20.5 mV/fC,and the linearity reaches 99.2%.
基金Project supported by the Beijing Municipal Natural Science Foundation,China(Grant No.4162030)the National Science and Technology Major Project of China(Grant No.2013ZX02303002)
文摘The comprehensive understanding of the structure-dependent electrostatic discharge behaviors in a conventional diode-triggered silicon controlled rectifier （DTSCR） is presented in this paper. Combined with the device simulation, a mathematical model is built to get a more in-depth insight into this phenomenon. The theoretical studies are verified by the transmission-line-pulsing （TLP） test results of the modified DTSCR structure, which is realized in a 65-nm complementary metal-oxide-semiconductor （CMOS） process. The detailed analysis of the physical mechanism is used to provide predictions as the DTSCR-based protection scheme is required. In addition, a method is also presented to achieve the tradeoff between the leakage and trigger voltage in DTSCR.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00601)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2009ZX02035-001)the National Natural Science Foundation of China(Grant Nos.60625403,60806033,and 60925015)
文摘Nitrogen plasma passivation （NPP） on （111） germanium （Ge） was studied in terms of the interface trap density, roughness, and interfacial layer thickness using plasma-enhanced chemical vapor deposition （PECVD）. The results show that NPP not only reduces the interface states, but also improves the surface roughness of Ge, which is beneficial for suppressing the channel scattering at both low and high field regions of Ge MOSFETs. However, the interracial layer thickness is also increased by the NPP treatment, which will impact the equivalent oxide thickness （EOT） scaling and thus degrade the device performance gain from the improvement of the surface morphology and the interface passivation. To obtain better device performance of Ge MOSFETs, suppressing the interfacial layer regrowth as well as a trade-off with reducing the interface states and roughness should be considered carefully when using the NPP process.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00601)the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2009ZX02035-001)the National Natural Science Foundation of China(Grant Nos.60625403,60806033,and 60925015)
文摘An extensive and complete experimental investigation with a full layout design of the channel direction was carried out for the first time to clarify the orientation dependence of germanium p-channel metal-oxide-semiconductor field-effect transistors （PMOSFETs）. By comparison of gate trans-conductance, drive current, and hole mobility, we found that the performance trend with the substrate orientation for Ge PMOSFET is （110）〉（111） ~ （100）, and the best channel direction is （110）/[110]. Moreover, the （110） device performance was found to be easily degraded as the channel direction got off from the [ 110] orientation, while （100） and （111） devices exhibited less channel orientation dependence. This experimental result shows good matching with the simulation reports to give a credible and significant guidance for Ge PMOSFET design.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB302705)the Foundation for Key Program of Ministry of Education, China (Grant No. 107003)
文摘In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si （110） nanowire via the simulation of strain distribution and the calculation of a generalized 6 × 6k .p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO2 insulator, the strain of the HfO2 gate insulator in Si （110） nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design.
基金This work was supported by the National Natural Science Foundation of China(61622401,61851402,and 61734003)National Key Research and Development Program(2017YFB0405600)+1 种基金Shanghai Education Development Foundation and Shanghai Municipal Education Commission Shuguang Program(18SG01)P.Z.also acknowledges support from Shanghai Municipal Science and Technology Commission(grant no.18JC1410300).
文摘Memory cells have always been an important element of information technology.With emerging technologies like big data and cloud computing,the scale and complexity of data storage has reached an unprecedented peak with a much higher requirement for memory technology.As is well known,better data storage is mostly achieved by miniaturization.However,as the size of the memory device is reduced,a series of problems,such as drain gate-induced leakage,greatly hinder the performance of memory units.To meet the increasing demands of information technology,novel and high-performance memory is urgently needed.Fortunately,emerging memory technologies are expected to improve memory performance and drive the information revolution.This review will focus on the progress of several emerging memory technologies,including two-dimensional material-based memories,resistance random access memory(RRAM),magnetic random access memory(MRAM),and phasechange random access memory(PCRAM).Advantages,mechanisms,and applications of these diverse memory technologies will be discussed in this review.
基金supported by the National Basic Research Program of China(Grant No.2011CBA00601)the National Natural Science Foundation of China(Grant Nos.60625403,60806033,and 60925015)
文摘In this paper, oxidation of Ge surface by N2O plasma is presented and experimentally demonstrated. Results show that 1.0-nm GeO2 is achieved after 120-s N20 plasma oxidation at 300 ℃. The GeO2/Ge interface is atomically smooth. The interface state density of Ge surface after N20 plasma passivation is about - 3 × 1011 cm-2.eV-1. With GeO2 passivation, the hysteresis of metal-oxide-semiconductor （MOS） capacitor with A1203 serving as gate dielectric is reduced to - 50 mV, compared with - 130 mV of the untreated one. The Fermi-level at GeO2/Ge interface is unpinned, and the surface potential is effectively modulated by the gate voltage.
文摘The effects of the physical damages induced by heavy ion irradiation on the performance of partiallydepleted SOI devices are experimentally investigated. After heavy ion exposure, different degradation phenomena are observed due to the random strike of heavy ions. A decrease of the saturation current and transconductance,and an enhanced gate-induced drain leakage current are observed, which are mainly attributed to the displacement damages that may be located in the channel, the depletion region of the drain/body junction or the gate-to-drain overlap region. Further, PDSOI devices with and without body contact are compared, which reveals the differences in the threshold voltage shift, the drain-induced barrier lowing effect, the transconductance and the kink effect. The results may provide a guideline for radiation hardened design.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61306104 and 61250014, the Postdoctoral Science Foundation of China under Grant No 2013M540018, and the National Basic Research Program of China under Grant No 2011CBA00604.
文摘The dynamics of electron transport in single-layer MoS2 is simulated by employing the single particle Monte Carlo method. Acoustic phonon scattering, optical phonon scattering and Frohlich scattering are taken into account. It is found that the electron mobility decreases from 806cm2 /V.s for a transverse electrical field of 103 Vim to 426/112 cm2 /V.s for a transverse electrical field of 105/107 Vim. Further detailed analysis on carrier dynamics reveals that the low field mobility is dominated by the acoustic phonon scattering while the role of optical phonon scattering is to relax the electron energy below the optical phonon energy by efficient energy relaxation through optical phonon emission. Only when the transverse electrical field is larger than 106 V/m, the mobility can be determined by the optical phonon scattering, leading to a strong mobility degradation.
基金Project supported by National Natural Science Foundation of China (Grant No. 60876027)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 200800010054)
文摘This paper studies an oxide/silicon core/shell nanowire MOSFET （OS-CSNM）. Through three-dimensional device simulations, we have demonstrated that the OS-CSNM has a lower leakage current and higher Ion/Ioff ratio after intro- ducing the oxide core into a traditional nanowire MOSFET （TNM）. The oxide/silicon OS-CSNM structure suppresses threshold voltage roll-off, drain induced barrier lowering and subthreshold swing degradation. Smaller intrinsic device delay is also observed in OS-CSNM in comparison with that of TNM.
基金supported by the National Natural Science Foundation of China(No.51972310)the Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences(CAS)+1 种基金the Youth Innovation Promotion Association,CAS(No.2011152)the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)(No.U1501501).
文摘Noble nanometals are of significance in both scientific interest and technological applications,which are usually obtained by conventional wet-chemical synthesis.Organic surfactants are always used in the synthesis to prevent unexpected overgrowth and aggregation of noble nanometals.However,the surfactants are hard to remove and may interfere with plasmonic and catalytic studies,remaining surfactant-free synthesis of noble nanometals a challenge.Herein,we report an approach to epitaxial growth of sizecontrolled noble nanometals on MXenes.As piloted by density functional theory calculations,along with work function experimental determination,kinetic and spectroscopic studies,epitaxial growth of noble nanometals is initiated via a mechanism that involves an in situ redox reaction.In the redox,MXenes as two-dimensional solid reductants whose work functions are compatible with the reduction potentials of noble metal cations,enable spontaneous donation of electrons from the MXenes to noble metal cations and reduce the cations into nanoscale metallic metals on the outmost surface of MXenes.Neither surfactants nor external reductants are used during the whole synthesis process,which addresses a long-standing interference issue of surfactant and external reductant in the conventional wet-chemical synthesis.Moreover,the MXenes induced noble nanometals are size-controlled.Impressively,noble nanometals firmly anchored on MXenes exhibit excellent performance towards surface enhanced Raman scattering.Our developed strategy will promote the nanostructure-controlled synthesis of noble nanometals,offering new opportunities to further improve advanced functional properties towards practical applications.
文摘A novel voltage controlled oscillator （VCO） sub-band selection circuit to achieve fast phase locked loop （PLL） calibration is presented, which reduces the calibration time by measuring the period difference directly and accomplishing an efficient search for an optimum VCO sub-band. The sub-band selection circuit was implemented in a 0.18 μm CMOS logic process with a PLL using an 8 sub-band VCO. The measured calibration time is less than 3 μs in a VCO frequency range from 600 MHz to 2 GHz. The proposed circuit consumes 0.64 mA at most.
文摘The radiation response of 90 nm bulk silicon MOS devices after heavy ion irradiation is experimentally investigated. Due to the random strike of the incident particle, different degradation behaviors of bulk silicon MOS devices are observed. The drain current and maximum transconductance degrade as a result of the displacement damage in the channel induced by heavy ion strike. The off-state leakage current degradation and threshold voltage shift are also observed after heavy ion irradiation. The results suggest that the radiation induced damage of sub-100 nm MOS devices caused by heavy ion irradiation should be paid attention.
基金supported by the National Natural Science Foundation of China(No.61176099)the Open Project of the State Key Laboratory of Functional Materials for Informatics,China
文摘In the design of phase-change memory（PCM）,it is important to perform numerical simulations to predict the performances of different device structures.This work presents a numerical simulation using a coupled system including Poisson＇s equation,the current continuity equation,the thermal conductivity equation,and phase-change dynamics to simulate the thermal and electric characteristics of phase-change memory.This method discriminates the common numerical simulation of PCM cells,from which it applies Possion＇s equation and current continuity equations instead of the Laplace equation to depict the electric characteristics of PCM cells,which is more adoptable for the semiconductor characteristics of phase-change materials.The results show that the simulation agrees with the measurement,and the scalability of PCM is predicted.
文摘The impact of process induced variation on the response of SOI Fin FET to heavy ion irradiation is studied through 3-D TCAD simulation for the first time. When Fin FET biased at OFF state configuration（Vgs D0, Vds DVdd/ is struck by a heavy ion, the drain collects ionizing charges under the electric field and a current pulse（single event transient, SET） is consequently formed. The results reveal that with the presence of line-edge roughness（LER）, which is one of the major variation sources in nano-scale Fin FETs, the device-to-device variation in terms of SET is observed. In this study, three types of LER are considered： type A has symmetric fin edges, type B has irrelevant fin edges and type C has parallel fin edges. The results show that type A devices have the largest SET variation while type C devices have the smallest variation. Further, the impact of the two main LER parameters,correlation length and root mean square amplitude, on SET variation is discussed as well. The results indicate that variation may be a concern in radiation effects with the down scaling of feature size.
基金China Postdoctoral Science Foundation,Grant/Award Number:2019T120183Beijing NOVA Programme,Grant/Award Number:Z131101000413038+3 种基金Chinese Academy of Sciences,Grant/Award Number:XDB12030300Ministry of Science and Technology of China,Grant/Award Number:2017YFA0204503Beijing Local College Innovation Team Improve Plan,Grant/Award Number:IDHT20140512National Natural Science Foundation of China,Grant/Award Numbers:91833306,51903186,21875158。
文摘Memristors proposed by Leon Chua provide a new type of memory device for novel neuromorphic computing applications.However,the approaching of distinct multi‐intermediate states for tunable switching dynamics,the con-trolling of conducting filaments(CFs)toward high device repeatability and reproducibility,and the ability for large‐scale preparation devices,remain full of challenges.Here,we show that vertical‐organic‐nanocrystal‐arrays(VONAs)could make a way toward the challenges.The perfect one‐dimensional structure of the VONAs could confine the CFs accurately with fine‐tune resistance states in a broad range of 103 ratios.The availability of large‐area VONAs makes the fabrication of large‐area crossbar memristor arrays facilely,and the analog switching characteristic of the memristors is to effectively imitate different kinds of synaptic plasticity,indicating their great potential in future applications.
基金supported by the Beijing Natural Science Foundation,China(No.4162030)
文摘The diode-triggered silicon-controlled rectifier（DTSCR） is widely used for electrostatic discharge（ESD） protection in advanced CMOS process owing to its advantages, such as design simplification, adjustable trigger/holding voltage, low parasitic capacitance. However, the multiple-triggering effect in the typical DTSCR device may cause undesirable larger overall trigger voltage, which results in a reduced ESD safe margin. In previous research, the major cause is attributed to the higher current level required in the intrinsic SCR. The related discussions indicate that it seems to result from the current division rule between the intrinsic and parasitic SCR formed in the triggering process. In this letter, inserting a large space into the trigger diodes is proposed to get a deeper insight into this issue. The triggering current is observed to be regularly reduced along with the increased space, which confirms that the current division is determined by the parasitic resistance distributed between the intrinsic and parasitic SCR paths. The theoretical analysis is well confirmed by device simulation and transmission line pulse（TLP） test results. The reduced overall trigger voltage is achieved in the modified DTSCR structures due to the comprehensive result of the parasitic resistance vs triggering current, which indicates a minimized multipletriggering effect.
基金Project supported by the National Science Fund for Distinguished Young Scholars of China(No.60925015)
文摘Traditional feedforward structures suffer from performance constraints caused by the complex adder before quantizer.This paper presents an improved 4th-order 1 -bit sigma-delta modulator which has a simple adder and delayed input feedforward to relax timing constraints and implement low-distortion.The modulator was fabricated in a 0.35μm CMOS process,and it achieved 92.8 dB SNDR and 101 dB DR with a signal bandwidth of 100 kHz dissipating 8.6 mW power from a 3.3-V supply.The performance satisfies the requirements of a GSM system.
文摘This paper describes an 8-bit 125 MHz low-power CMOS fully-folding analog-to-digital converter （ADC） A novel mixed-averaging distributed T/H circuit is proposed to improve the accuracy. Folding circuits are not only used in the fine converter but also in the coarse one and in the bit synchronization block to reduce the number of comparators for low power. This ADC is implemented in 0.5μm CMOS technology and occupies a die area of 2 × 1.5 mm^2. The measured differential nonlinearity and integral nonlinearity are 0.6 LSB/-0.8 LSB and 0.9 LSB/-1.2 LSB, respectively. The ADC exhibits 44.3 dB of signal-to-noise plus distortion ratio and 53.5 dB of spurious-free dynamic range for 1 MHz input sine-wave. The power dissipation is 138 mW at a sampling rate of 125 MHz at a 5 V supply.
