This paper reviews the original achievements and advances regarding the field effect transistor(FET) fabricated from one of the most studied transition metal dichalcogenides: two-dimensional Mo S2. Not like graphene, ...This paper reviews the original achievements and advances regarding the field effect transistor(FET) fabricated from one of the most studied transition metal dichalcogenides: two-dimensional Mo S2. Not like graphene, which is highlighted by a gapless Dirac cone band structure, Monolayer Mo S2 is featured with a 1.9 e V gapped direct energy band thus facilitates convenient electronic and/or optoelectronic modulation of its physical properties in FET structure. Indeed,many Mo S2 devices based on FET architecture such as phototransistors, memory devices, and sensors have been studied and extraordinary properties such as excellent mobility, ON/OFF ratio, and sensitivity of these devices have been exhibited. However, further developments in FET device applications depend a lot on if novel physics would be involved in them. In this review, an overview on advances and developments in the Mo S2-based FETs are presented. Engineering of Mo S2-based FETs will be discussed in details for understanding contact physics, formation of gate dielectric, and doping strategies. Also reported are demonstrations of device behaviors such as low-frequency noise and photoresponse in Mo S2-based FETs, which is crucial for developing electronic and optoelectronic devices.展开更多
Power electronic devices are of great importance in modern society.After decades of development,Si power devices have approached their material limits with only incremental improvements and large conversion losses.As ...Power electronic devices are of great importance in modern society.After decades of development,Si power devices have approached their material limits with only incremental improvements and large conversion losses.As the demand for electronic components with high efficiency dramatically increasing,new materials are needed for power device fabrication.Betaphase gallium oxide,an ultra-wide bandgap semiconductor,has been considered as a promising candidate,and variousβ-Ga_(2)O_(3)power devices with high breakdown voltages have been demonstrated.However,the realization of enhancement-mode(E-mode)β-Ga_(2)O_(3)field-effect transistors(FETs)is still challenging,which is a critical problem for a myriad of power electronic applications.Recently,researchers have made some progress on E-modeβ-Ga_(2)O_(3)FETs via various methods,and several novel structures have been fabricated.This article gives a review of the material growth,devices and properties of these E-modeβ-Ga_(2)O_(3)FETs.The key challenges and future directions in E-modeβ-Ga_(2)O_(3)FETs are also discussed.展开更多
A NiO/β-Ga_(2)O_(3) heterojunction-gate field effect transistor(HJ-FET)is fabricated and it_(s)instability mechanisms are exper-imentally investigated under different gate stress voltage(V_(G,s))and stress times(t_(s...A NiO/β-Ga_(2)O_(3) heterojunction-gate field effect transistor(HJ-FET)is fabricated and it_(s)instability mechanisms are exper-imentally investigated under different gate stress voltage(V_(G,s))and stress times(t_(s)).Two different degradation mechanisms of the devices under negative bias stress(NBS)are identified.At low V_(G,s)for a short t_(s),NiO bulk traps trapping/de-trapping elec-trons are responsible for decrease/recovery of the leakage current,respectively.At higher V_(G,s)or long t_(s),the device transfer char-acteristic curves and threshold voltage(V_(TH))are almost permanently negatively shifted.This is because the interface dipoles are almost permanently ionized and neutralize the ionized charges in the space charge region(SCR)across the heterojunction inter-face,resulting in a narrowing SCR.This provides an important theoretical guide to study the reliability of NiO/β-Ga_(2)O_(3) hetero-junction devices in power electronic applications.展开更多
In this paper, we propose multi-fin FET design techniques targeted for RF applications. Overlap and underlap design configuration in a base FinFET are compared first and then multi-fin device (consisting of transistor...In this paper, we propose multi-fin FET design techniques targeted for RF applications. Overlap and underlap design configuration in a base FinFET are compared first and then multi-fin device (consisting of transistor unit up to 50) is studied to develop design limitations and to evaluate their effects on the device performance. We have also investigated the impact of the number of fins (up to 50) in multi-fin structure and resulting RF parameters. Our results show that as the number of fin increases, underlap design compromises RF performance and short channel effects. The results provide technical understanding that is necessary to realize new opportunities for RF and analog mixed-signal design with nanoscale FinFETs.展开更多
For the development of ultra-sensitive electrical bio/chemical sensors based on nanowire field effect transistors （FETs）, the influence of the ions in the solution on the electron transport has to be understood. For...For the development of ultra-sensitive electrical bio/chemical sensors based on nanowire field effect transistors （FETs）, the influence of the ions in the solution on the electron transport has to be understood. For this purpose we establish a simulation platform for nanowire FETs in the liquid environment by implementing the modified Poisson-Boltzmann model into Landauer transport theory. We investigate the changes of the electric potential and the transport characteristics due to the ions. The reduction of sensitivity of the sensors due to the screening effect from the electrolyte could be successfully reproduced. We also fabricated silicon nanowire Schottky-barrier FETs and our model could capture the observed reduction of the current with increasing ionic concentration. This shows that our simulation platform can be used to interpret ongoing experiments, to design nanowire FETs, and it also gives insight into controversial issues such as whether ions in the buffer solution affect the transport characteristics or not.展开更多
A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate（CSG） MOSFETs has been developed.Based on this a subthreshold drai...A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate（CSG） MOSFETs has been developed.Based on this a subthreshold drain current model has also been derived.This model first computes the charge induced in the drain/source region due to the fringing capacitances and considers an effective charge distribution in the cylindrically extended source/drain region for the development of a simple and compact model.The fringing gate capacitances taken into account are outer fringe capacitance,inner fringe capacitance,overlap capacitance,and sidewall capacitance.The model has been verified with the data extracted from 3D TCAD simulations of CSG MOSFETs and was found to be working satisfactorily.展开更多
In this paper,RF performance analysis of In As-based double gate（DG）tunnel field effect transistors（TFETs）is investigated in both qualitative and quantitative fashion.This investigation is carried out by varying t...In this paper,RF performance analysis of In As-based double gate（DG）tunnel field effect transistors（TFETs）is investigated in both qualitative and quantitative fashion.This investigation is carried out by varying the geometrical and doping parameters of TFETs to extract various RF parameters,unity gain cut-off frequency（f_t）,maximum oscillation frequency（f_（max））,intrinsic gain and admittance（Y）parameters.An asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs.Higher ON-current（ION）of about 0.2 mA and less leakage current（IOFF）of 29 f A is achieved for DG TFET with gate-drain overlap.Due to increase in transconductance（g_m）,higher ft and intrinsic gain is attained for DG TFET with gate-drain overlap.Higher f_（max） of 985 GHz is obtained for drain doping of 5×10^（17）cm^（-3） because of the reduced gate-drain capacitance（C_（gd））with DG TFET with gate-drain overlap.In terms of Y-parameters,gate oxide thickness variation offers better performance due to the reduced values of Cgd.A second order numerical polynomial model is generated for all the RF responses as a function of geometrical and doping parameters.The simulation results are compared with this numerical model where the predicted values match with the simulated values.展开更多
The newly emerged two-dimensional(2D) semiconducting materials, owning to the atomic thick nature and excellent optical and electrical properties, are considered as potential candidates to solve the bottlenecks of tra...The newly emerged two-dimensional(2D) semiconducting materials, owning to the atomic thick nature and excellent optical and electrical properties, are considered as potential candidates to solve the bottlenecks of traditional semiconductors. However, the realization of high performance 2D semiconductorbased field-effect transistors(FETs) has been a longstanding challenge in 2D electronics, which is mainly ascribing to the presence of significant Schottky barrier(SB) at metal-semiconductor interfaces. Here, an additional contact gate is induced in 2D ambipolar FET to realize near ideal reconfigurable FET(RFET)devices without restrictions of SB. Benefitting from the consistently high doping of contact region, the effective SB height can be maintained at ultra-small value during all operation conditions, resulting in the near ideal subthreshold swing(SS) values(132 mV/decade for MoTe2 RFET and 67 mV/decade for WSe2 RFET) and the relatively high mobility(28.6 cm2/(Vs) for MoTe2 RFET and 89.8 cm2/(V s) for WSe2 RFET). Moreover, the flexible control on the doping polarity of contact region enables the remodeling and switching of the achieved unipolar FETs between p-type mode and n-type mode. Based on such reconfigurable behaviors, high gain complementary MoTe2 inverters are further realized. The findings in this work push forward the development of high-performance 2D semiconductor integrated devices and circuits.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
In this work,a surface-potential based compact model focusing on the quantum confinement effects of ultimately scaled gate-all-around(GAA)MOSFET is presented.Energy quantization with sub-band formation along the radiu...In this work,a surface-potential based compact model focusing on the quantum confinement effects of ultimately scaled gate-all-around(GAA)MOSFET is presented.Energy quantization with sub-band formation along the radius direction of cylindrical GAAs or thickness direction of nanosheet GAAs leads to significant quantization effects.An analytical model of surface potentials is developed by solving the Poisson equation with incorporating sub-band effects.In combination with the existing transport model framework,charge-voltage and current-voltage formulations are developed based on the surface potential.The model formulations are then extensively validated using TCAD numerical simulations as well as Si data of nanosheet GAA MOSFETs.Simulations of typical circuits verify the model robustness and convergence for its applications in GAA technology.展开更多
A much more sustainable,cost effective and very flexible process for manufacturing critical fibres based on ultra high molecular weight polyethylene(UHMWPE)is being launched by the UK’s Fibre Extrusion Technologies(F...A much more sustainable,cost effective and very flexible process for manufacturing critical fibres based on ultra high molecular weight polyethylene(UHMWPE)is being launched by the UK’s Fibre Extrusion Technologies(FET).展开更多
Two-dimensional transition metal dichalcogenides(TMDs)show great promise for developing the next generation of electronic and optoelectronic devices.However,most TMDs have n-type or n-dominant bipolar characteristics,...Two-dimensional transition metal dichalcogenides(TMDs)show great promise for developing the next generation of electronic and optoelectronic devices.However,most TMDs have n-type or n-dominant bipolar characteristics,and this severely limits their potential for being designed as multi-functional heterostructures.Recently,thermal annealing has been reported as an easy means of p-doping TMDs,but the mechanism remains ambiguous,thereby preventing reliable outcomes and it becoming a mature doping technology for TMDs.Here,the mechanism of thermal annealing for p-doping a 2D selenide is investigated thoroughly,revealing the key role of the catalytic effect of nano-thick gold electrodes in achieving p-doping.As an example,2D SnSe_(2)with a fairly high electron density of∼10^(18)cm^(−3)is used,and its electrical performance is greatly enhanced after thermal annealing when 30-nm-thick gold electrodes are deposited.The results of performing XPS and Auger electron spectroscopy on samples before and after annealing show that the p-doping effect is due to the oxidation of selenide atoms,during which the gold acts as a critical catalytic element.This method is also shown to be valid for other 2D selenides including WSe_(2)and MoSe_(2),and the present findings offer new avenues for enriching the electrical properties of 2D selenides by means of annealing.展开更多
The rise in gas leakage incidents underscores the urgent need for advanced gas-sensing platforms with ultra-low concentration detection capability.Sensing gate field effect transistor(FET)gas sensors,renowned for the ...The rise in gas leakage incidents underscores the urgent need for advanced gas-sensing platforms with ultra-low concentration detection capability.Sensing gate field effect transistor(FET)gas sensors,renowned for the gas-induced signal amplification without directly exposing the channel to the ambient environment,play a pivotal role in detecting trace-level hazardous gases with high sensitivity and good stability.In this work,carbon nanotubes are employed as the conducting channel,and yttrium oxide(Y_(2)O_(3))is utilized as the gate dielectric layer.Noble metal Pd is incorporated as a sensing gate for hydrogen(H_(2))detection,leveraging its catalytic properties and unique adsorption capability.The fabricated carbon-based FET gas sensor demonstrates a remarkable detection limit of 20×10^(–9) for H_(2) under an air environment,enabling early warning in case of gas leakage.Moreover,the as-prepared sensor exhibited good selectivity,repeatability,and anti-humidity properties.Further experiments elucidate the interaction between H_(2) and sensing electrode under an air/nitrogen environment,providing insights into the underlying oxygen-assisted recoverable sensing mechanism.It is our aspiration for this research to establish a robust experimental foundation for achieving high performance and highly integrated fabrication of trace gas sensors.展开更多
This study was conducted to determine the content,distribution and transformation of iron oxides in the soils of the Middle Euphrates regions in Iraq.The study included four sites:Tuwairij area in Karbala Governorate,...This study was conducted to determine the content,distribution and transformation of iron oxides in the soils of the Middle Euphrates regions in Iraq.The study included four sites:Tuwairij area in Karbala Governorate,College of Agriculture at the University of Kufa in Najaf Governorate,College of Agriculture at the University of Qadisiyah in Diwaniyah Governorate,and the Nile District in Babylon Governorate.The results showed that the soils of Najaf and Qadisiyah were superior in terms of their content of total free iron oxides(Fet)compared to the soils of Karbala and Babylon.The relative distribution of free iron oxides was generally close among the studied sites,with a homogeneous pattern in the distribution of these oxides within the soil horizons.As for silicate iron oxides(Fes),a homogeneous pattern was observed in the soil of Babylon with its content increasing with depth,while these patterns varied in the soils of Karbala,Najaf and Qadisiyah.Regarding the ratios of crystalline iron oxides(Fed/Fet),the study showed that the Babylon and Qadisiyah soils recorded the highest values,while these values were lower in the Najaf and Karbala soils.On the other hand,amorphous iron oxides(FeO)showed similar values in the Najaf and Qadisiyah soils.In general,these results clearly showed the effect of environmental and geochemical factors of the study areas on the distribution and transformations of iron oxides in the soil of the Middle Euphrates regions.展开更多
文摘This paper reviews the original achievements and advances regarding the field effect transistor(FET) fabricated from one of the most studied transition metal dichalcogenides: two-dimensional Mo S2. Not like graphene, which is highlighted by a gapless Dirac cone band structure, Monolayer Mo S2 is featured with a 1.9 e V gapped direct energy band thus facilitates convenient electronic and/or optoelectronic modulation of its physical properties in FET structure. Indeed,many Mo S2 devices based on FET architecture such as phototransistors, memory devices, and sensors have been studied and extraordinary properties such as excellent mobility, ON/OFF ratio, and sensitivity of these devices have been exhibited. However, further developments in FET device applications depend a lot on if novel physics would be involved in them. In this review, an overview on advances and developments in the Mo S2-based FETs are presented. Engineering of Mo S2-based FETs will be discussed in details for understanding contact physics, formation of gate dielectric, and doping strategies. Also reported are demonstrations of device behaviors such as low-frequency noise and photoresponse in Mo S2-based FETs, which is crucial for developing electronic and optoelectronic devices.
基金supported in part by the National Basic Research Program of China(Grant No.2021YFB3600202)Key Laboratory Construction Project of Nanchang(Grant No.2020-NCZDSY-008)the Suzhou Science and Technology Foundation(Grant No.SYG202027)。
文摘Power electronic devices are of great importance in modern society.After decades of development,Si power devices have approached their material limits with only incremental improvements and large conversion losses.As the demand for electronic components with high efficiency dramatically increasing,new materials are needed for power device fabrication.Betaphase gallium oxide,an ultra-wide bandgap semiconductor,has been considered as a promising candidate,and variousβ-Ga_(2)O_(3)power devices with high breakdown voltages have been demonstrated.However,the realization of enhancement-mode(E-mode)β-Ga_(2)O_(3)field-effect transistors(FETs)is still challenging,which is a critical problem for a myriad of power electronic applications.Recently,researchers have made some progress on E-modeβ-Ga_(2)O_(3)FETs via various methods,and several novel structures have been fabricated.This article gives a review of the material growth,devices and properties of these E-modeβ-Ga_(2)O_(3)FETs.The key challenges and future directions in E-modeβ-Ga_(2)O_(3)FETs are also discussed.
基金supported by the Fundamental Strengthening Program Key Basic Research Project(Grant No.2021-173ZD-057).
文摘A NiO/β-Ga_(2)O_(3) heterojunction-gate field effect transistor(HJ-FET)is fabricated and it_(s)instability mechanisms are exper-imentally investigated under different gate stress voltage(V_(G,s))and stress times(t_(s)).Two different degradation mechanisms of the devices under negative bias stress(NBS)are identified.At low V_(G,s)for a short t_(s),NiO bulk traps trapping/de-trapping elec-trons are responsible for decrease/recovery of the leakage current,respectively.At higher V_(G,s)or long t_(s),the device transfer char-acteristic curves and threshold voltage(V_(TH))are almost permanently negatively shifted.This is because the interface dipoles are almost permanently ionized and neutralize the ionized charges in the space charge region(SCR)across the heterojunction inter-face,resulting in a narrowing SCR.This provides an important theoretical guide to study the reliability of NiO/β-Ga_(2)O_(3) hetero-junction devices in power electronic applications.
文摘In this paper, we propose multi-fin FET design techniques targeted for RF applications. Overlap and underlap design configuration in a base FinFET are compared first and then multi-fin device (consisting of transistor unit up to 50) is studied to develop design limitations and to evaluate their effects on the device performance. We have also investigated the impact of the number of fins (up to 50) in multi-fin structure and resulting RF parameters. Our results show that as the number of fin increases, underlap design compromises RF performance and short channel effects. The results provide technical understanding that is necessary to realize new opportunities for RF and analog mixed-signal design with nanoscale FinFETs.
文摘For the development of ultra-sensitive electrical bio/chemical sensors based on nanowire field effect transistors （FETs）, the influence of the ions in the solution on the electron transport has to be understood. For this purpose we establish a simulation platform for nanowire FETs in the liquid environment by implementing the modified Poisson-Boltzmann model into Landauer transport theory. We investigate the changes of the electric potential and the transport characteristics due to the ions. The reduction of sensitivity of the sensors due to the screening effect from the electrolyte could be successfully reproduced. We also fabricated silicon nanowire Schottky-barrier FETs and our model could capture the observed reduction of the current with increasing ionic concentration. This shows that our simulation platform can be used to interpret ongoing experiments, to design nanowire FETs, and it also gives insight into controversial issues such as whether ions in the buffer solution affect the transport characteristics or not.
基金Project supported by the AICTE(No.8023/BOR/RID/RPS-253/2008-09)the SMDP-Ⅱ Project(No.21(1)/2005-VCND) by MCIT, DeiTy,Govt of India
文摘A physically based analytical model for surface potential and threshold voltage including the fringing gate capacitances in cylindrical surround gate（CSG） MOSFETs has been developed.Based on this a subthreshold drain current model has also been derived.This model first computes the charge induced in the drain/source region due to the fringing capacitances and considers an effective charge distribution in the cylindrically extended source/drain region for the development of a simple and compact model.The fringing gate capacitances taken into account are outer fringe capacitance,inner fringe capacitance,overlap capacitance,and sidewall capacitance.The model has been verified with the data extracted from 3D TCAD simulations of CSG MOSFETs and was found to be working satisfactorily.
基金Project supported by the Department of Science and Technology,Government of India under SERB Scheme(No.SERB/F/2660)
文摘In this paper,RF performance analysis of In As-based double gate（DG）tunnel field effect transistors（TFETs）is investigated in both qualitative and quantitative fashion.This investigation is carried out by varying the geometrical and doping parameters of TFETs to extract various RF parameters,unity gain cut-off frequency（f_t）,maximum oscillation frequency（f_（max））,intrinsic gain and admittance（Y）parameters.An asymmetric gate oxide is introduced in the gate-drain overlap and compared with that of DG TFETs.Higher ON-current（ION）of about 0.2 mA and less leakage current（IOFF）of 29 f A is achieved for DG TFET with gate-drain overlap.Due to increase in transconductance（g_m）,higher ft and intrinsic gain is attained for DG TFET with gate-drain overlap.Higher f_（max） of 985 GHz is obtained for drain doping of 5×10^（17）cm^（-3） because of the reduced gate-drain capacitance（C_（gd））with DG TFET with gate-drain overlap.In terms of Y-parameters,gate oxide thickness variation offers better performance due to the reduced values of Cgd.A second order numerical polynomial model is generated for all the RF responses as a function of geometrical and doping parameters.The simulation results are compared with this numerical model where the predicted values match with the simulated values.
基金supported by the National Natural Science Foundation of China (U19A2090, 51902098, 51972105, 51525202, and 61574054)the Hunan Provincial Natural Science Foundation (2018RS3051)。
文摘The newly emerged two-dimensional(2D) semiconducting materials, owning to the atomic thick nature and excellent optical and electrical properties, are considered as potential candidates to solve the bottlenecks of traditional semiconductors. However, the realization of high performance 2D semiconductorbased field-effect transistors(FETs) has been a longstanding challenge in 2D electronics, which is mainly ascribing to the presence of significant Schottky barrier(SB) at metal-semiconductor interfaces. Here, an additional contact gate is induced in 2D ambipolar FET to realize near ideal reconfigurable FET(RFET)devices without restrictions of SB. Benefitting from the consistently high doping of contact region, the effective SB height can be maintained at ultra-small value during all operation conditions, resulting in the near ideal subthreshold swing(SS) values(132 mV/decade for MoTe2 RFET and 67 mV/decade for WSe2 RFET) and the relatively high mobility(28.6 cm2/(Vs) for MoTe2 RFET and 89.8 cm2/(V s) for WSe2 RFET). Moreover, the flexible control on the doping polarity of contact region enables the remodeling and switching of the achieved unipolar FETs between p-type mode and n-type mode. Based on such reconfigurable behaviors, high gain complementary MoTe2 inverters are further realized. The findings in this work push forward the development of high-performance 2D semiconductor integrated devices and circuits.
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supported in part by the Natural Science Foundation of China(62125401 and 62074006)the major scientific instruments and equipments development grant(61927901)the Shenzhen Fundamental Research Program(GXWD20200827114656001).
文摘In this work,a surface-potential based compact model focusing on the quantum confinement effects of ultimately scaled gate-all-around(GAA)MOSFET is presented.Energy quantization with sub-band formation along the radius direction of cylindrical GAAs or thickness direction of nanosheet GAAs leads to significant quantization effects.An analytical model of surface potentials is developed by solving the Poisson equation with incorporating sub-band effects.In combination with the existing transport model framework,charge-voltage and current-voltage formulations are developed based on the surface potential.The model formulations are then extensively validated using TCAD numerical simulations as well as Si data of nanosheet GAA MOSFETs.Simulations of typical circuits verify the model robustness and convergence for its applications in GAA technology.
文摘A much more sustainable,cost effective and very flexible process for manufacturing critical fibres based on ultra high molecular weight polyethylene(UHMWPE)is being launched by the UK’s Fibre Extrusion Technologies(FET).
基金supported by the National Natural Science Foundation of China(Grant Nos.52075385 and 12034001)the National Key R&D Program(Grant No.2018YFA0307200)the 111 Project(Grant No.B07014).
文摘Two-dimensional transition metal dichalcogenides(TMDs)show great promise for developing the next generation of electronic and optoelectronic devices.However,most TMDs have n-type or n-dominant bipolar characteristics,and this severely limits their potential for being designed as multi-functional heterostructures.Recently,thermal annealing has been reported as an easy means of p-doping TMDs,but the mechanism remains ambiguous,thereby preventing reliable outcomes and it becoming a mature doping technology for TMDs.Here,the mechanism of thermal annealing for p-doping a 2D selenide is investigated thoroughly,revealing the key role of the catalytic effect of nano-thick gold electrodes in achieving p-doping.As an example,2D SnSe_(2)with a fairly high electron density of∼10^(18)cm^(−3)is used,and its electrical performance is greatly enhanced after thermal annealing when 30-nm-thick gold electrodes are deposited.The results of performing XPS and Auger electron spectroscopy on samples before and after annealing show that the p-doping effect is due to the oxidation of selenide atoms,during which the gold acts as a critical catalytic element.This method is also shown to be valid for other 2D selenides including WSe_(2)and MoSe_(2),and the present findings offer new avenues for enriching the electrical properties of 2D selenides by means of annealing.
基金supported by the National Natural Science Foundation of China(Nos.62071410 and 62101477)Hunan Provincial Natural Science Foundation(No.2021JJ40542).
文摘The rise in gas leakage incidents underscores the urgent need for advanced gas-sensing platforms with ultra-low concentration detection capability.Sensing gate field effect transistor(FET)gas sensors,renowned for the gas-induced signal amplification without directly exposing the channel to the ambient environment,play a pivotal role in detecting trace-level hazardous gases with high sensitivity and good stability.In this work,carbon nanotubes are employed as the conducting channel,and yttrium oxide(Y_(2)O_(3))is utilized as the gate dielectric layer.Noble metal Pd is incorporated as a sensing gate for hydrogen(H_(2))detection,leveraging its catalytic properties and unique adsorption capability.The fabricated carbon-based FET gas sensor demonstrates a remarkable detection limit of 20×10^(–9) for H_(2) under an air environment,enabling early warning in case of gas leakage.Moreover,the as-prepared sensor exhibited good selectivity,repeatability,and anti-humidity properties.Further experiments elucidate the interaction between H_(2) and sensing electrode under an air/nitrogen environment,providing insights into the underlying oxygen-assisted recoverable sensing mechanism.It is our aspiration for this research to establish a robust experimental foundation for achieving high performance and highly integrated fabrication of trace gas sensors.
文摘This study was conducted to determine the content,distribution and transformation of iron oxides in the soils of the Middle Euphrates regions in Iraq.The study included four sites:Tuwairij area in Karbala Governorate,College of Agriculture at the University of Kufa in Najaf Governorate,College of Agriculture at the University of Qadisiyah in Diwaniyah Governorate,and the Nile District in Babylon Governorate.The results showed that the soils of Najaf and Qadisiyah were superior in terms of their content of total free iron oxides(Fet)compared to the soils of Karbala and Babylon.The relative distribution of free iron oxides was generally close among the studied sites,with a homogeneous pattern in the distribution of these oxides within the soil horizons.As for silicate iron oxides(Fes),a homogeneous pattern was observed in the soil of Babylon with its content increasing with depth,while these patterns varied in the soils of Karbala,Najaf and Qadisiyah.Regarding the ratios of crystalline iron oxides(Fed/Fet),the study showed that the Babylon and Qadisiyah soils recorded the highest values,while these values were lower in the Najaf and Karbala soils.On the other hand,amorphous iron oxides(FeO)showed similar values in the Najaf and Qadisiyah soils.In general,these results clearly showed the effect of environmental and geochemical factors of the study areas on the distribution and transformations of iron oxides in the soil of the Middle Euphrates regions.
