Nanowires have emerged as promising one-dimensional materials with which to construct various nanocircuits and nanosensors.However,measuring the electrical properties of individual nanowires directly remains challengi...Nanowires have emerged as promising one-dimensional materials with which to construct various nanocircuits and nanosensors.However,measuring the electrical properties of individual nanowires directly remains challenging because of their small size,thereby hindering the comprehensive understanding of nanowire-based device performance.A crucial factor in achieving reliable electrical characterization is establishing well-determined contact conditions between the nanowire sample and the electrodes,which becomes particularly difficult for soft nanowires.Introduced here is a novel technique for measuring the conductivity of an individual nanowire with the aid of automated nanomanipulation using an atomic force microscope.In this method,two nanowire segments cut from the same silver nanowire are positioned onto a pair of gold electrodes,serving as flexible nanoprobes to establish controllable contact with the sample.By changing the contact points along the nanowire sample,conductivity measurements can be performed on different regions,thereby eliminating the influence of contact resistance by analyzing multiple current–voltage curves.Using this approach,the resistivity of a 100-nm-diameter silver nanowire is determined to be 3.49×10^(−8)Ωm.展开更多
Using hexagonal boron nitride(h-BN)to prepare resistive switching devices is a promising strategy.Various doping methods have aroused great interest in the semiconductor field in recent years,but many researchers have...Using hexagonal boron nitride(h-BN)to prepare resistive switching devices is a promising strategy.Various doping methods have aroused great interest in the semiconductor field in recent years,but many researchers have overlooked the various repetitive anomalies that occur during the testing process.In this study,the basic electrical properties and additive protrusion behavior of Ga-ion-doped h-BN memristors at micro–nanoscale during the voltage scanning process are investigated via atomic force microscopy(AFM)and energy dispersive spectroscopy.The additive protrusion behavior is subjected to exploratory research,and it is concluded that it is caused by anodic oxidation.An approach is proposed that involves filling the AFM chamber with nitrogen gas to improve the stability of memristor testing,and this method provides a solution for enhanced testing stability of memristors.展开更多
Layered ReS_(2) with direct bandgap and strong in-plane anisotropy shows great potential to develop high-performance angle-resolved photodetectors and optoelectronic devices.However,systematic characterizations of the...Layered ReS_(2) with direct bandgap and strong in-plane anisotropy shows great potential to develop high-performance angle-resolved photodetectors and optoelectronic devices.However,systematic characterizations of the angle-dependent photoresponse of ReS_(2) are still very limited.Here,we studied the anisotropic photoresponse of layered ReS_(2) phototransistors in depth.Angel-resolved Raman spectrum and field-effect mobility are tested to confirm the inconsistency between its electrical and optical anisotropies,which are along 120°and 90°,respectively.We further measured the angle-resolved photoresponse of a ReS_(2) transistor with 6 diagonally paired electrodes.The maximum photoresponsivity exceeds 0.515 A·W^(-1) along b-axis,which is around 3.8 times larger than that along the direction perpendicular to b axis,which is consistent with the optical anisotropic directions.The incident wavelength-and power-dependent photoresponse measurement along two anisotropic axes further demonstrates that b axis has stronger light-ReS_(2) interaction,which explains the anisotropic photoresponse.We also observed angle-dependent photoresistive switching behavior of the ReS_(2) transistor,which leads to the formation of angle-resolved phototransistor memory.It has simplified structure to create dynamic optoelectronic resistive random access memory controlled spatially through polarized light.This capability has great potential for real-time pattern recognition and photoconfiguration of artificial neural networks(ANN)in a wide spectral range of sensitivity provided by polarized light.展开更多
2D material of graphene has inspired huge interest in fabricating of solid state gas sensors.In this work,epitaxial graphene,quasi-free-standing graphene,and CVD epitaxial graphene samples on SiC substrates are used t...2D material of graphene has inspired huge interest in fabricating of solid state gas sensors.In this work,epitaxial graphene,quasi-free-standing graphene,and CVD epitaxial graphene samples on SiC substrates are used to fabricate gas sensors.Defects are introduced into graphene using SF6 plasma treatment to improve the performance of the gas sensors.The epitaxial graphene shows high sensitivity to NO2 with response of 105.1%to 4 ppm NO2 and detection limit of 1 ppb.The higher sensitivity of epitaxial graphene compared to quasi-free-standing graphene,and CVD epitaxial graphene was found to be related to the different doping types of the samples.展开更多
Flash memories and semiconductor p-n junctions are two elementary but incompatible building blocks of most electronic and optoelectronic devices.The pressing demand to efficiently transfer massive data between memorie...Flash memories and semiconductor p-n junctions are two elementary but incompatible building blocks of most electronic and optoelectronic devices.The pressing demand to efficiently transfer massive data between memories and logic circuits,as well as for high data storage capability and device integration density,has fueled the rapid growth of technique and material innovations.Two-dimensional(2D)materials are considered as one of the most promising candidates to solve this challenge.However,a key aspect for 2D materials to build functional devices requires effective and accurate control of the carrier polarity,concentration and spatial distribution in the atomically thin structures.Here,a non-volatile opto-electrical doping approach is demonstrated,which enables reversibly writing spatially resolved doping patterns in the MoTe2 conductance channel through a MoTe2/hexagonal boron nitride(h-BN)heterostructure.Based on the doping effect induced by the combination of electrostatic modulation and ultraviolet light illumination,a 3-bit flash memory and various homojunctions on the same MoTe2/BN heterostructure are successfully developed.The flash memory achieved 8 well distinguished memory states with a maximum on/off ratio over 10^4.Each state showed negligible decay during the retention time of 2,400 s.The heterostructure also allowed the formation of p-p,n-n,p-n,and n-p homojunctions and the free transition among these states.The MoTe2 p-n homojunction with a rectification ratio of 10^3 exhibited excellent photodetection and photovoltaic performance.Having the memory device and p-n junction built on the same structure makes it possible to bring memory and computational circuit on the same chip,one step further to realize near-memory computing.展开更多
Atomically thin two-dimensional(2D)materials are promising candidates to develop flash memories with premium performances as compared to conventional bulk materials,because of their ultra-thin thickness and highly tun...Atomically thin two-dimensional(2D)materials are promising candidates to develop flash memories with premium performances as compared to conventional bulk materials,because of their ultra-thin thickness and highly tunable electrical properties.So far,most of the reported 2D material based flash memories work in the uni-polar mode,which usually further integrate additional local gate to achieve bi-polar function.However,such approach is volatile,meaning that the gate bias has to be applied persistently to maintain the polarity change and thus increases the power consumption.Here,we report a bi-polar memory based on MoTe_(2)/h-BN/graphene semi-floating gate(SFG)heterostructure,which has non-volatile and dynamically tunable polarity.The SFG configuration has the channel layer of MoTe_(2) and dielectric layer of h-BN half-stacked on the floating gate layer of graphene.The off-graphene half of the MoTe_(2) channel can be tuned between n-type and p-type by simultaneously applying ultraviolet(UV)illumination and electrical field through the back gate,which maintains this polarity after the removal of both stimuli.As a result,the SFG memory can work in the non-volatile bi-polar mode,with a on/off ratio of~100 and switching speed of 1 ms.On the other hand,the on-graphene half of the MoTe_(2) channel remains n-type under UV illumination and electrical bias,so that the MoTe_(2) full floating gate memory maintains n-type,which implements the integration of both n-and p-type memories in a single 2D heterostructure.This capability provides great flexibility for memory devices adapting in various emerging applications.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.61973233).
文摘Nanowires have emerged as promising one-dimensional materials with which to construct various nanocircuits and nanosensors.However,measuring the electrical properties of individual nanowires directly remains challenging because of their small size,thereby hindering the comprehensive understanding of nanowire-based device performance.A crucial factor in achieving reliable electrical characterization is establishing well-determined contact conditions between the nanowire sample and the electrodes,which becomes particularly difficult for soft nanowires.Introduced here is a novel technique for measuring the conductivity of an individual nanowire with the aid of automated nanomanipulation using an atomic force microscope.In this method,two nanowire segments cut from the same silver nanowire are positioned onto a pair of gold electrodes,serving as flexible nanoprobes to establish controllable contact with the sample.By changing the contact points along the nanowire sample,conductivity measurements can be performed on different regions,thereby eliminating the influence of contact resistance by analyzing multiple current–voltage curves.Using this approach,the resistivity of a 100-nm-diameter silver nanowire is determined to be 3.49×10^(−8)Ωm.
基金supported by the Youth Fund of the National Natural Science Foundation of China(Grant No.622041701004267).
文摘Using hexagonal boron nitride(h-BN)to prepare resistive switching devices is a promising strategy.Various doping methods have aroused great interest in the semiconductor field in recent years,but many researchers have overlooked the various repetitive anomalies that occur during the testing process.In this study,the basic electrical properties and additive protrusion behavior of Ga-ion-doped h-BN memristors at micro–nanoscale during the voltage scanning process are investigated via atomic force microscopy(AFM)and energy dispersive spectroscopy.The additive protrusion behavior is subjected to exploratory research,and it is concluded that it is caused by anodic oxidation.An approach is proposed that involves filling the AFM chamber with nitrogen gas to improve the stability of memristor testing,and this method provides a solution for enhanced testing stability of memristors.
文摘Layered ReS_(2) with direct bandgap and strong in-plane anisotropy shows great potential to develop high-performance angle-resolved photodetectors and optoelectronic devices.However,systematic characterizations of the angle-dependent photoresponse of ReS_(2) are still very limited.Here,we studied the anisotropic photoresponse of layered ReS_(2) phototransistors in depth.Angel-resolved Raman spectrum and field-effect mobility are tested to confirm the inconsistency between its electrical and optical anisotropies,which are along 120°and 90°,respectively.We further measured the angle-resolved photoresponse of a ReS_(2) transistor with 6 diagonally paired electrodes.The maximum photoresponsivity exceeds 0.515 A·W^(-1) along b-axis,which is around 3.8 times larger than that along the direction perpendicular to b axis,which is consistent with the optical anisotropic directions.The incident wavelength-and power-dependent photoresponse measurement along two anisotropic axes further demonstrates that b axis has stronger light-ReS_(2) interaction,which explains the anisotropic photoresponse.We also observed angle-dependent photoresistive switching behavior of the ReS_(2) transistor,which leads to the formation of angle-resolved phototransistor memory.It has simplified structure to create dynamic optoelectronic resistive random access memory controlled spatially through polarized light.This capability has great potential for real-time pattern recognition and photoconfiguration of artificial neural networks(ANN)in a wide spectral range of sensitivity provided by polarized light.
基金supported by the National Natural Science Foundation of China (61674131 and 61306006)
文摘2D material of graphene has inspired huge interest in fabricating of solid state gas sensors.In this work,epitaxial graphene,quasi-free-standing graphene,and CVD epitaxial graphene samples on SiC substrates are used to fabricate gas sensors.Defects are introduced into graphene using SF6 plasma treatment to improve the performance of the gas sensors.The epitaxial graphene shows high sensitivity to NO2 with response of 105.1%to 4 ppm NO2 and detection limit of 1 ppb.The higher sensitivity of epitaxial graphene compared to quasi-free-standing graphene,and CVD epitaxial graphene was found to be related to the different doping types of the samples.
基金This work is supported by the National Natural Science Foundation of China(No.21405109)Seed Foundation of State Key Laboratory of Precision Measurement Technology and Instruments,China(No.Pilt1710).
文摘Flash memories and semiconductor p-n junctions are two elementary but incompatible building blocks of most electronic and optoelectronic devices.The pressing demand to efficiently transfer massive data between memories and logic circuits,as well as for high data storage capability and device integration density,has fueled the rapid growth of technique and material innovations.Two-dimensional(2D)materials are considered as one of the most promising candidates to solve this challenge.However,a key aspect for 2D materials to build functional devices requires effective and accurate control of the carrier polarity,concentration and spatial distribution in the atomically thin structures.Here,a non-volatile opto-electrical doping approach is demonstrated,which enables reversibly writing spatially resolved doping patterns in the MoTe2 conductance channel through a MoTe2/hexagonal boron nitride(h-BN)heterostructure.Based on the doping effect induced by the combination of electrostatic modulation and ultraviolet light illumination,a 3-bit flash memory and various homojunctions on the same MoTe2/BN heterostructure are successfully developed.The flash memory achieved 8 well distinguished memory states with a maximum on/off ratio over 10^4.Each state showed negligible decay during the retention time of 2,400 s.The heterostructure also allowed the formation of p-p,n-n,p-n,and n-p homojunctions and the free transition among these states.The MoTe2 p-n homojunction with a rectification ratio of 10^3 exhibited excellent photodetection and photovoltaic performance.Having the memory device and p-n junction built on the same structure makes it possible to bring memory and computational circuit on the same chip,one step further to realize near-memory computing.
基金supported by the National Key R&D Program(No.2018YFA0307200)the National Science Foundation of China(NSFC,No.52075385 and 12034001)the 111 Project(No.B07014).
文摘Atomically thin two-dimensional(2D)materials are promising candidates to develop flash memories with premium performances as compared to conventional bulk materials,because of their ultra-thin thickness and highly tunable electrical properties.So far,most of the reported 2D material based flash memories work in the uni-polar mode,which usually further integrate additional local gate to achieve bi-polar function.However,such approach is volatile,meaning that the gate bias has to be applied persistently to maintain the polarity change and thus increases the power consumption.Here,we report a bi-polar memory based on MoTe_(2)/h-BN/graphene semi-floating gate(SFG)heterostructure,which has non-volatile and dynamically tunable polarity.The SFG configuration has the channel layer of MoTe_(2) and dielectric layer of h-BN half-stacked on the floating gate layer of graphene.The off-graphene half of the MoTe_(2) channel can be tuned between n-type and p-type by simultaneously applying ultraviolet(UV)illumination and electrical field through the back gate,which maintains this polarity after the removal of both stimuli.As a result,the SFG memory can work in the non-volatile bi-polar mode,with a on/off ratio of~100 and switching speed of 1 ms.On the other hand,the on-graphene half of the MoTe_(2) channel remains n-type under UV illumination and electrical bias,so that the MoTe_(2) full floating gate memory maintains n-type,which implements the integration of both n-and p-type memories in a single 2D heterostructure.This capability provides great flexibility for memory devices adapting in various emerging applications.