Blue-green electroluminescence has been observed in free-standing diamond films which were deposited by microwave plasma assisted CVD on silicon substrates.The electroluminescence device is driven by a 60 Hz power sup...Blue-green electroluminescence has been observed in free-standing diamond films which were deposited by microwave plasma assisted CVD on silicon substrates.The electroluminescence device is driven by a 60 Hz power supply.The threshold voltage was about 112 V peak-to-peak.The electroluminescence spectrum at room temperature,showed a blue-green band with the peak centered at 485nm suggesting band A type emission.Electroluminescence was also observed at 77K.展开更多
Blue electroluminescence of boron doped diamond thin film is reported.The boron doped diamond thin films were deposited by microwave plasma assisted chemical vapor deposition on silicon substrate.The electroluminescen...Blue electroluminescence of boron doped diamond thin film is reported.The boron doped diamond thin films were deposited by microwave plasma assisted chemical vapor deposition on silicon substrate.The electroluminescence device was driven by a frequency-modulated power supply.The optimum frequency is near 3 kHz.The dependence of electroluminescence intensity on boron impurity has been investigated.The intensity increases with increasing boron impurity.This is expected result according to“Band A”electroluminescence mechanism of donor-accepter pairs recombination.展开更多
This paper presents a study on thickness dependent physical properties of cadmium selenide thin films. The films of thickness 445, 631 and 810 nm were deposited employing thermal evaporation technique on glass and ITO...This paper presents a study on thickness dependent physical properties of cadmium selenide thin films. The films of thickness 445, 631 and 810 nm were deposited employing thermal evaporation technique on glass and ITO-coated glass substrates followed by thermal annealing in air atmosphere at 200 °C. These films were subjected to X-ray diffractometer, UV-Vis spectrophotometer, scanning electron microscopy（SEM） and electrometer for structural, optical,surface morphological and electrical analysis respectively. The structural analysis reveals that the films are nanocrystalline in nature with cubic phase and preferred orientation（111）. The crystallographic parameters such as lattice constant, interplanar spacing, grain size, internal strain, dislocation density, number of crystallites per unit area and texture coefficient are calculated and discussed. The optical band gap is found in the range 1.75-1.92 e V and observed to increase with thickness.The SEM study shows that the annealed films are uniform, fully covered and well defined. The electrical analysis shows that the conductivity is varied with film thickness and found within the order of semiconductor behavior.展开更多
The rapidly developing perovskite solar cells(PSCs) provide a new and promising choice of thin film solar cells due to their attractive attributes.Among the commercialized thin film solar cells,CuInGaSe(CIGS)cells dem...The rapidly developing perovskite solar cells(PSCs) provide a new and promising choice of thin film solar cells due to their attractive attributes.Among the commercialized thin film solar cells,CuInGaSe(CIGS)cells demonstrate higher efficiency than amorphous Si photovoltaic devices and lower toxicity than CdTe cells.Therefore,a wide variety of studies have been conducted on them.Here,we elucidate CIGS materials and perovskites as absorber in thin film solar cells in terms of structure and optoelectronic properties.Furthermore,a comparison of PSCs and commercialized CIGS cells is made from the point of view of fabrication process,stability,and toxicity.In addition,the integration of CIGS devices and PSCs is elaborated based on tandem architecture.Finally,prospects for the advancement of CIGS cells and PSCs are discussed.展开更多
The effects of Cd^(2+) ions on the microstructure,magnetic properties,and dielectric properties of Bi_(2)O_(3)-added MgFe_(2)O_(4) ferrites(Cd_(x)Mg_(1-x)Fe_(2)O_(4),x=0.00,0.15,0.30 and 0.45)are obtained by adopting ...The effects of Cd^(2+) ions on the microstructure,magnetic properties,and dielectric properties of Bi_(2)O_(3)-added MgFe_(2)O_(4) ferrites(Cd_(x)Mg_(1-x)Fe_(2)O_(4),x=0.00,0.15,0.30 and 0.45)are obtained by adopting the solid-state reaction method at a low temperature(910℃).The objective is to achieve matching impedances,low magnetic and dielectric losses(tanδμand tanδε,respectively),and a relatively large miniaturization factor to reduce antenna size.Experimental results indicate that the cations occupying the tetrahedral(A)and octahedral(B)ion sites are redistributed,resulting in an enhanced super-exchange interaction between the two sublattices.As a result,improved magnetization,including the increase in saturation magnetization(41.74 emu/g)and decrease in coercivity(63.75 Oe),is realized.The real part of permeability(μ')also increases with increasing concentration of Cd^(2+) ions.When x is 0.15,matching impedances with equivalent μ'and ε'values are obtained over a long frequency range(1–150MHz).Moreover,the formation of a dense microstructure guarantees that losses occur at low orders of magnitude(tanδμ≈10−2 and tanδε≈10−3).Accordingly,these properties afford wide application perspectives for the proposed compounds in the high-frequency region,i.e.,from high-frequency to very-high-frequency bands.展开更多
Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics, high index contrast, small footprint, and low cost, as well as its optical t...Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics, high index contrast, small footprint, and low cost, as well as its optical transparency in the nearinfrared and parts of mid-infrared(MIR) wavelengths(from 1.1 to 8 μm). While considerations of micro-and nano-fabrication-induced device parameter deviations and a higher-than-desirable propagation loss still serve as a bottleneck in many on-chip data communication applications, applications as sensors do not require similar stringent controls. Photonic devices on chips are increasingly being demonstrated for chemical and biological sensing with performance metrics rivaling benchtop instruments and thus promising the potential of portable, handheld,and wearable monitoring of various chemical and biological analytes. In this paper, we review recent advances in MIR silicon photonics research. We discuss the pros and cons of various platforms, the fabrication procedures for building such platforms, and the benchmarks demonstrated so far, together with their applications. Novel device architectures and improved fabrication techniques have paved a viable way for realizing low-cost, high-density,multi-function integrated devices in the MIR. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.展开更多
Mid-infrared vibrational spectroscopy is a universal label-free tool for identifying molecular compounds in chemical and biological samples on the basis of their‘fingerprint’vibrational absorption lines.Vibrational ...Mid-infrared vibrational spectroscopy is a universal label-free tool for identifying molecular compounds in chemical and biological samples on the basis of their‘fingerprint’vibrational absorption lines.Vibrational spectroscopy with nanometer spatial resolution can reveal the chemical composition of samples at the nanoscale,and several scanning-probe techniques have been developed to address this need1–22.It is also highly desirable to study biological and chemical samples in their native aqueous environments rather than in air.In aqueous environments,however,the sensitivity of the current vibrational nanospectroscopy techniques deteriorates dramatically7,23.Here,we report the first mid-infrared nanospectroscopy technique that retains nanoscale sensitivity and spatial resolution when the sample and the scanning probe are completely immersed in water.This method overcomes challenges including water absorption and scattering and the mechanical damping of cantilever vibrations.We further demonstrate spectroscopy and imaging of 20-to 50-nmthick polymer samples with a 25-nm spatial resolution in the biologically relevant Amide I and II spectral regions.展开更多
The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semicond...The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density.Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials.We present InAs plasmonic disk arrays as a viable resonant metamaterial at terahertz frequencies.Importantly,InAs plasmonic disks exhibit a strong nonlinear response arising from electric field-induced intervalley scattering,resulting in a reduced carrier mobility thereby damping the plasmonic response.We demonstrate nonlinear perfect absorbers configured as either optical limiters or saturable absorbers,including flexible nonlinear absorbers achieved by transferring the disks to polyimide films.Nonlinear plasmonic metamaterials show potential for use in ultrafast terahertz(THz)optics and for passive protection of sensitive electromagnetic devices.展开更多
We propose a heterostructure junctionless tunnel field effect transistor （HJL-TFET） using AIGaAs/Si. In the proposed HJL-TFET, low band gap silicon is used in the source side and higher band gap AlGaAs in the drain ...We propose a heterostructure junctionless tunnel field effect transistor （HJL-TFET） using AIGaAs/Si. In the proposed HJL-TFET, low band gap silicon is used in the source side and higher band gap AlGaAs in the drain side. The whole AlGaAs/Si region is heavily doped n-type. The proposed HJL-TFET uses two isolated gates （named gate, gatel ） with two different work functions （gate = 4.2 eV, gatel = 5.2 eV respectively）. The 2-D nature of HJL-TFET current flow is studied. The proposed structure is simulated in Silvaco with different gate dielectric materials. This structure exhibits a high on current in the range of 1.4 × 10^-6 A/μm, the off current remains as low as 9.1 × 10^-14 A/μm. So /ON/OFF ratio of 10^8 is achieved. Point subthreshold swing has also been reduced to a value of 41 mV/decade for TiO2 gate material.展开更多
For the first time, we investigate the temperature effect on AIGaAs/Si based hetero-structure junction- less double gate tunnel field effect transistor. Since junctionless tunnel FET is an alternative substitute devic...For the first time, we investigate the temperature effect on AIGaAs/Si based hetero-structure junction- less double gate tunnel field effect transistor. Since junctionless tunnel FET is an alternative substitute device for ultra scaled deep-submicron CMOS technology, having very good device characteristics such as an improved sub- threshold slope （〈 60 mV/decade at 300 K） and very small static leakage currents. The improved subthreshold slope and static leakage current confirms that it will be helpful for the development of future low power switching circuits. The 2-D computer based simulation results show that OFF-state leakage current is almost temperature independent for the proposed device structure.展开更多
This paper proposes a novel design paradigm for circuits designed in quantum dot cellular automata （QCA） technology. Previously reported QCA circuits in the literature have generally been designed in a single layer ...This paper proposes a novel design paradigm for circuits designed in quantum dot cellular automata （QCA） technology. Previously reported QCA circuits in the literature have generally been designed in a single layer which is the main logical block in which the inverter and majority gate are on the base layer, except for the parts where multilayer wire crossing was used. In this paper the concept of multilayer wire crossing has been extended to design logic gates in multilayers. Using a 5-input majority gate in a multilayer, a 1-bit and 2-bit adder have been designed in the proposed multilayer gate design paradigm. A comparison has been made with some adders reported previously in the literature and it has been shown that circuits designed in the proposed design paradigm are much more efficient in terms of area, the requirement of QCA cells in the design and the input-output delay of the circuit. Over all, the availability of one additional spatial dimension makes the design process much more flexible and there is scope for the customizability of logic gate designs to make the circuit compact.展开更多
We propose a hetero-gate-dielectric double gate junctionless transistor （HGJLT）, taking high-k gate insulator at source side and low-k gate insulator at drain side, which reduces the effects ＆band-to-band tunnelli...We propose a hetero-gate-dielectric double gate junctionless transistor （HGJLT）, taking high-k gate insulator at source side and low-k gate insulator at drain side, which reduces the effects ＆band-to-band tunnelling （BTBT） in the sub-threshold region. A junctionless transistor （JLT） is turned off by the depletion of carriers in the highly doped thin channel （device layer） which results in a significant band overlap between the valence band of the channel region and the conduction band of the drain region, due to off-state drain bias, that triggers electrons to tunnel from the valence band of the channel region to the conduction band of the drain region leaving behind holes in the channel.These effects of band-to-band tunnelling increase the sub-threshold leakage current, and the accumulation of holes in the channel forms a parasitic bipolar junction transistor （n-p-n BJT for channel JLT） in the lateral direction by the source （emitter）, channel （base） and drain （collector） regions in JLT structure in off-state. The proposed HGJLT reduces the subthreshold leakage current and suppresses the parasitic BJT action in off-state by reducing the band-to-band tunnelling probability.展开更多
We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types： armchair and zigzag. WTe2 in its bulk form h...We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types： armchair and zigzag. WTe2 in its bulk form has an indirect band gap but nanoribbons and nanosheets of WTe2 have direct band gaps. Interestingly, the zigzag nanoribbon is metallic while the armchair nanoribbons are semiconducting. Thus they can find applications in device fabrication. Therefore, it is very important to study the effect of defects on the electronic properties of the armchair nanoribbons as these defects can impair the device properties and characteristics. We have considered defects such as： vacancy, rough edge, wrap, ripple and twist in this work. We report the band gap variation with these defects. We have also studied the change in band gap and total energy with varying degrees of wrap, ripple and twist.展开更多
For the first time, we investigate the analog performance of n-type double gate junctionless tunnel field effect transistor （DG-JLTFET） and the results are compared with the conventional n-type double gate tunnel fi...For the first time, we investigate the analog performance of n-type double gate junctionless tunnel field effect transistor （DG-JLTFET） and the results are compared with the conventional n-type double gate tunnel field effect transistor （DG-TFET） counterpart. Using extensive device simulations, the two devices are compared with the following analog performance parameters, namely transconductance, output conductance, output resistance, intrinsic gain, total gate capacitance and unity gain frequency. From the device simulation results, DG-JLTFET is found to have significantly better analog performance as compared to DG-TFET.展开更多
We propose a nanoscale single gate ultra thin body intrinsic channel tunnel field effect transistor using the charge plasma concept for ultra low power applications. The characteristics of TFETs （having low leakage）...We propose a nanoscale single gate ultra thin body intrinsic channel tunnel field effect transistor using the charge plasma concept for ultra low power applications. The characteristics of TFETs （having low leakage） are improved by junctionless TFETs through blending advantages of Junctionless FETs （with high on current）. We further improved the characteristics, simultaneously simplifying the structure at a very low power rating using an InAs channel. We found that the proposed device structure has reduced short channel effects and parasitics and provides high speed operation even at a very low supply voltage with low leakage. Simulations resulted in Iovv of - 9 × 10-16A/um, IoN of ,-20uA/um, ION/IoFF of--2× 1010, threshold voltage of 0.057 V, subthreshold slope of 7 mV/dec and DIBL of 86 mV/V for PolyGate/HfO2/InAs TFET at a temperature of 300 K, gate length of 20 nm, oxide thickness of 2 nm, film thickness of 10 nm, low-k spacer thickness of 10 nm and VDD of 0.2 V.展开更多
This paper describes a tape nanolithography method for the rapid and economical manufacturing of flexible,wearable nanophotonic devices.This method involves the soft lithography of a donor substrate with air-void nano...This paper describes a tape nanolithography method for the rapid and economical manufacturing of flexible,wearable nanophotonic devices.This method involves the soft lithography of a donor substrate with air-void nanopatterns,subsequent deposition of materials onto the substrate surface,followed by direct taping and peeling of the deposited materials by an adhesive tape.Without using any sophisticated techniques,the nanopatterns,which are preformed on the surface of the donor substrate,automatically emerge in the deposited materials.The nanopatterns can then be transferred to the tape surface.By leveraging the works of adhesion at the interfaces of the donor substrate-deposited material-tape assembly,this method not only demonstrates sub-hundred-nanometer resolution in the transferred nanopatterns on an area of multiple square inches but also exhibits high versatility and flexibility for configuring the shapes,dimensions,and material compositions of tape-supported nanopatterns to tune their optical properties.After the tape transfer,the materials that remain at the bottom of the air-void nanopatterns on the donor substrate exhibit shapes complementary to the transferred nanopatterns on the tape surface but maintain the same composition,thus also acting as functional nanophotonic structures.Using tape nanolithography,we demonstrate several tapesupported plasmonic,dielectric,and metallo-dielectric nanostructures,as well as several devices such as refractive index sensors,conformable plasmonic surfaces,and Fabry-Perot cavity resonators.Further,we demonstrate tape nanolithography-assisted manufacturing of a standalone plasmonic nanohole film and its transfer to unconventional substrates such as a cleaved facet and the curved side of an optical fiber.展开更多
Blue electroluminescence of diamond thin film has already been investigated by some authors. To our knowledge, ultraviolet electroluminescence of diamond thin film has not been reported so far. We have prepared an ele...Blue electroluminescence of diamond thin film has already been investigated by some authors. To our knowledge, ultraviolet electroluminescence of diamond thin film has not been reported so far. We have prepared an electroluminescence device with展开更多
We have investigated the 20 nm p-type double gate junctionless tunnel field effect transistor （P-DGJLTFET） and the impact of variation of different device parameters on the performance parameters of the P-DGJLTFET i...We have investigated the 20 nm p-type double gate junctionless tunnel field effect transistor （P-DGJLTFET） and the impact of variation of different device parameters on the performance parameters of the P-DGJLTFET is discussed. We achieved excellent results of different performance parameters by taking the optimized device parameters of the P-DGJLTFET. Together with a high-k dielectric material （TiO2） of 20 nm gate length, the simulation results of the P-DGJLTFET show excellent characteristics with a high IoN of ～ 0.3 mA/μm, a low/OFF of ～ 30 fA/μm, a high ION/IOFF ratio of ～ 1×10^10, a subthreshold slope （SS） point of ～ 23 mV/decade, and an average SS of ～ 49 mV/decade at a supply voltage of -1 V and at room temperature, which indicates that PDGJLTFET is a promising candidate for sub-22 nm technology nodes in the implementation of integrated circuits.展开更多
基金the National Natural Science Foundation of China,and the Natural Science Foundation of He'nan province.
文摘Blue-green electroluminescence has been observed in free-standing diamond films which were deposited by microwave plasma assisted CVD on silicon substrates.The electroluminescence device is driven by a 60 Hz power supply.The threshold voltage was about 112 V peak-to-peak.The electroluminescence spectrum at room temperature,showed a blue-green band with the peak centered at 485nm suggesting band A type emission.Electroluminescence was also observed at 77K.
基金Supported by the National Natural Science Foundation of Chinathe Natural Science。
文摘Blue electroluminescence of boron doped diamond thin film is reported.The boron doped diamond thin films were deposited by microwave plasma assisted chemical vapor deposition on silicon substrate.The electroluminescence device was driven by a frequency-modulated power supply.The optimum frequency is near 3 kHz.The dependence of electroluminescence intensity on boron impurity has been investigated.The intensity increases with increasing boron impurity.This is expected result according to“Band A”electroluminescence mechanism of donor-accepter pairs recombination.
基金financial support under UGC-BSR fellowship No.F.25-1/2013-14(BSR)/7-123/2007(BSR)
文摘This paper presents a study on thickness dependent physical properties of cadmium selenide thin films. The films of thickness 445, 631 and 810 nm were deposited employing thermal evaporation technique on glass and ITO-coated glass substrates followed by thermal annealing in air atmosphere at 200 °C. These films were subjected to X-ray diffractometer, UV-Vis spectrophotometer, scanning electron microscopy（SEM） and electrometer for structural, optical,surface morphological and electrical analysis respectively. The structural analysis reveals that the films are nanocrystalline in nature with cubic phase and preferred orientation（111）. The crystallographic parameters such as lattice constant, interplanar spacing, grain size, internal strain, dislocation density, number of crystallites per unit area and texture coefficient are calculated and discussed. The optical band gap is found in the range 1.75-1.92 e V and observed to increase with thickness.The SEM study shows that the annealed films are uniform, fully covered and well defined. The electrical analysis shows that the conductivity is varied with film thickness and found within the order of semiconductor behavior.
基金supported by the NSF NNCI grant ECCS-2025227 at the Texas Nanofabrication Facility。
文摘The rapidly developing perovskite solar cells(PSCs) provide a new and promising choice of thin film solar cells due to their attractive attributes.Among the commercialized thin film solar cells,CuInGaSe(CIGS)cells demonstrate higher efficiency than amorphous Si photovoltaic devices and lower toxicity than CdTe cells.Therefore,a wide variety of studies have been conducted on them.Here,we elucidate CIGS materials and perovskites as absorber in thin film solar cells in terms of structure and optoelectronic properties.Furthermore,a comparison of PSCs and commercialized CIGS cells is made from the point of view of fabrication process,stability,and toxicity.In addition,the integration of CIGS devices and PSCs is elaborated based on tandem architecture.Finally,prospects for the advancement of CIGS cells and PSCs are discussed.
基金This work was supported by National Key Scientific Instrument and Equipment Development Project No.51827802by Major Science and Technology projects in Sichuan Province Nos.2019ZDZX0026 and 20ZDYF2818+1 种基金by the National Natural Science Foundation of China No.51872041by Foundation for University Teacher of Education of China No.ZYGX2019J011.
文摘The effects of Cd^(2+) ions on the microstructure,magnetic properties,and dielectric properties of Bi_(2)O_(3)-added MgFe_(2)O_(4) ferrites(Cd_(x)Mg_(1-x)Fe_(2)O_(4),x=0.00,0.15,0.30 and 0.45)are obtained by adopting the solid-state reaction method at a low temperature(910℃).The objective is to achieve matching impedances,low magnetic and dielectric losses(tanδμand tanδε,respectively),and a relatively large miniaturization factor to reduce antenna size.Experimental results indicate that the cations occupying the tetrahedral(A)and octahedral(B)ion sites are redistributed,resulting in an enhanced super-exchange interaction between the two sublattices.As a result,improved magnetization,including the increase in saturation magnetization(41.74 emu/g)and decrease in coercivity(63.75 Oe),is realized.The real part of permeability(μ')also increases with increasing concentration of Cd^(2+) ions.When x is 0.15,matching impedances with equivalent μ'and ε'values are obtained over a long frequency range(1–150MHz).Moreover,the formation of a dense microstructure guarantees that losses occur at low orders of magnitude(tanδμ≈10−2 and tanδε≈10−3).Accordingly,these properties afford wide application perspectives for the proposed compounds in the high-frequency region,i.e.,from high-frequency to very-high-frequency bands.
基金National Natural Science Foundation of China(NSFC)(61705099)Natural Science Foundation of Jiangsu Province,China(BK20160631)+3 种基金National Science Foundation(NSF)(IIP-1127251)U.S.Army(W911SR-12-C-004)National Institute of Standards and Technology(NIST)(70NANB16H183)National Aeronautics and Space Administration(NASA)(NNX17CA44P)
文摘Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics, high index contrast, small footprint, and low cost, as well as its optical transparency in the nearinfrared and parts of mid-infrared(MIR) wavelengths(from 1.1 to 8 μm). While considerations of micro-and nano-fabrication-induced device parameter deviations and a higher-than-desirable propagation loss still serve as a bottleneck in many on-chip data communication applications, applications as sensors do not require similar stringent controls. Photonic devices on chips are increasingly being demonstrated for chemical and biological sensing with performance metrics rivaling benchtop instruments and thus promising the potential of portable, handheld,and wearable monitoring of various chemical and biological analytes. In this paper, we review recent advances in MIR silicon photonics research. We discuss the pros and cons of various platforms, the fabrication procedures for building such platforms, and the benchmarks demonstrated so far, together with their applications. Novel device architectures and improved fabrication techniques have paved a viable way for realizing low-cost, high-density,multi-function integrated devices in the MIR. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.
基金support from the Robert A.Welch Foundation(grant no.F-1705)the US Department of Energy STTR program.
文摘Mid-infrared vibrational spectroscopy is a universal label-free tool for identifying molecular compounds in chemical and biological samples on the basis of their‘fingerprint’vibrational absorption lines.Vibrational spectroscopy with nanometer spatial resolution can reveal the chemical composition of samples at the nanoscale,and several scanning-probe techniques have been developed to address this need1–22.It is also highly desirable to study biological and chemical samples in their native aqueous environments rather than in air.In aqueous environments,however,the sensitivity of the current vibrational nanospectroscopy techniques deteriorates dramatically7,23.Here,we report the first mid-infrared nanospectroscopy technique that retains nanoscale sensitivity and spatial resolution when the sample and the scanning probe are completely immersed in water.This method overcomes challenges including water absorption and scattering and the mechanical damping of cantilever vibrations.We further demonstrate spectroscopy and imaging of 20-to 50-nmthick polymer samples with a 25-nm spatial resolution in the biologically relevant Amide I and II spectral regions.
基金supported in part by the National Science Foundation under contract ECCS 1309835the Air Force Office of Scientific Research under contract FA9550-09-1-0708+1 种基金support from DOEBasic Energy Sciences under Grant No.DE-FG02-09ER46643,under which the THz measurements were performedsupported by a Multidisciplinary University Research Initiative from the Air Force Office of Scientific Research(AFOSR MURI Award No.FA9550-12-1-0488)。
文摘The development of responsive metamaterials has enabled the realization of compact tunable photonic devices capable of manipulating the amplitude,polarization,wave vector and frequency of light.Integration of semiconductors into the active regions of metallic resonators is a proven approach for creating nonlinear metamaterials through optoelectronic control of the semiconductor carrier density.Metal-free subwavelength resonant semiconductor structures offer an alternative approach to create dynamic metamaterials.We present InAs plasmonic disk arrays as a viable resonant metamaterial at terahertz frequencies.Importantly,InAs plasmonic disks exhibit a strong nonlinear response arising from electric field-induced intervalley scattering,resulting in a reduced carrier mobility thereby damping the plasmonic response.We demonstrate nonlinear perfect absorbers configured as either optical limiters or saturable absorbers,including flexible nonlinear absorbers achieved by transferring the disks to polyimide films.Nonlinear plasmonic metamaterials show potential for use in ultrafast terahertz(THz)optics and for passive protection of sensitive electromagnetic devices.
文摘We propose a heterostructure junctionless tunnel field effect transistor （HJL-TFET） using AIGaAs/Si. In the proposed HJL-TFET, low band gap silicon is used in the source side and higher band gap AlGaAs in the drain side. The whole AlGaAs/Si region is heavily doped n-type. The proposed HJL-TFET uses two isolated gates （named gate, gatel ） with two different work functions （gate = 4.2 eV, gatel = 5.2 eV respectively）. The 2-D nature of HJL-TFET current flow is studied. The proposed structure is simulated in Silvaco with different gate dielectric materials. This structure exhibits a high on current in the range of 1.4 × 10^-6 A/μm, the off current remains as low as 9.1 × 10^-14 A/μm. So /ON/OFF ratio of 10^8 is achieved. Point subthreshold swing has also been reduced to a value of 41 mV/decade for TiO2 gate material.
文摘For the first time, we investigate the temperature effect on AIGaAs/Si based hetero-structure junction- less double gate tunnel field effect transistor. Since junctionless tunnel FET is an alternative substitute device for ultra scaled deep-submicron CMOS technology, having very good device characteristics such as an improved sub- threshold slope （〈 60 mV/decade at 300 K） and very small static leakage currents. The improved subthreshold slope and static leakage current confirms that it will be helpful for the development of future low power switching circuits. The 2-D computer based simulation results show that OFF-state leakage current is almost temperature independent for the proposed device structure.
文摘This paper proposes a novel design paradigm for circuits designed in quantum dot cellular automata （QCA） technology. Previously reported QCA circuits in the literature have generally been designed in a single layer which is the main logical block in which the inverter and majority gate are on the base layer, except for the parts where multilayer wire crossing was used. In this paper the concept of multilayer wire crossing has been extended to design logic gates in multilayers. Using a 5-input majority gate in a multilayer, a 1-bit and 2-bit adder have been designed in the proposed multilayer gate design paradigm. A comparison has been made with some adders reported previously in the literature and it has been shown that circuits designed in the proposed design paradigm are much more efficient in terms of area, the requirement of QCA cells in the design and the input-output delay of the circuit. Over all, the availability of one additional spatial dimension makes the design process much more flexible and there is scope for the customizability of logic gate designs to make the circuit compact.
文摘We propose a hetero-gate-dielectric double gate junctionless transistor （HGJLT）, taking high-k gate insulator at source side and low-k gate insulator at drain side, which reduces the effects ＆band-to-band tunnelling （BTBT） in the sub-threshold region. A junctionless transistor （JLT） is turned off by the depletion of carriers in the highly doped thin channel （device layer） which results in a significant band overlap between the valence band of the channel region and the conduction band of the drain region, due to off-state drain bias, that triggers electrons to tunnel from the valence band of the channel region to the conduction band of the drain region leaving behind holes in the channel.These effects of band-to-band tunnelling increase the sub-threshold leakage current, and the accumulation of holes in the channel forms a parasitic bipolar junction transistor （n-p-n BJT for channel JLT） in the lateral direction by the source （emitter）, channel （base） and drain （collector） regions in JLT structure in off-state. The proposed HGJLT reduces the subthreshold leakage current and suppresses the parasitic BJT action in off-state by reducing the band-to-band tunnelling probability.
基金the Department of Science and Technology of the government of India for partially funding this work
文摘We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types： armchair and zigzag. WTe2 in its bulk form has an indirect band gap but nanoribbons and nanosheets of WTe2 have direct band gaps. Interestingly, the zigzag nanoribbon is metallic while the armchair nanoribbons are semiconducting. Thus they can find applications in device fabrication. Therefore, it is very important to study the effect of defects on the electronic properties of the armchair nanoribbons as these defects can impair the device properties and characteristics. We have considered defects such as： vacancy, rough edge, wrap, ripple and twist in this work. We report the band gap variation with these defects. We have also studied the change in band gap and total energy with varying degrees of wrap, ripple and twist.
文摘For the first time, we investigate the analog performance of n-type double gate junctionless tunnel field effect transistor （DG-JLTFET） and the results are compared with the conventional n-type double gate tunnel field effect transistor （DG-TFET） counterpart. Using extensive device simulations, the two devices are compared with the following analog performance parameters, namely transconductance, output conductance, output resistance, intrinsic gain, total gate capacitance and unity gain frequency. From the device simulation results, DG-JLTFET is found to have significantly better analog performance as compared to DG-TFET.
文摘We propose a nanoscale single gate ultra thin body intrinsic channel tunnel field effect transistor using the charge plasma concept for ultra low power applications. The characteristics of TFETs （having low leakage） are improved by junctionless TFETs through blending advantages of Junctionless FETs （with high on current）. We further improved the characteristics, simultaneously simplifying the structure at a very low power rating using an InAs channel. We found that the proposed device structure has reduced short channel effects and parasitics and provides high speed operation even at a very low supply voltage with low leakage. Simulations resulted in Iovv of - 9 × 10-16A/um, IoN of ,-20uA/um, ION/IoFF of--2× 1010, threshold voltage of 0.057 V, subthreshold slope of 7 mV/dec and DIBL of 86 mV/V for PolyGate/HfO2/InAs TFET at a temperature of 300 K, gate length of 20 nm, oxide thickness of 2 nm, film thickness of 10 nm, low-k spacer thickness of 10 nm and VDD of 0.2 V.
基金This work was supported in part by the U.S.National Science Foundation under Grant No.ECCS-1711839in part by the Iowa State University’s Plant Sciences Institute through the Faculty Scholar Program.
文摘This paper describes a tape nanolithography method for the rapid and economical manufacturing of flexible,wearable nanophotonic devices.This method involves the soft lithography of a donor substrate with air-void nanopatterns,subsequent deposition of materials onto the substrate surface,followed by direct taping and peeling of the deposited materials by an adhesive tape.Without using any sophisticated techniques,the nanopatterns,which are preformed on the surface of the donor substrate,automatically emerge in the deposited materials.The nanopatterns can then be transferred to the tape surface.By leveraging the works of adhesion at the interfaces of the donor substrate-deposited material-tape assembly,this method not only demonstrates sub-hundred-nanometer resolution in the transferred nanopatterns on an area of multiple square inches but also exhibits high versatility and flexibility for configuring the shapes,dimensions,and material compositions of tape-supported nanopatterns to tune their optical properties.After the tape transfer,the materials that remain at the bottom of the air-void nanopatterns on the donor substrate exhibit shapes complementary to the transferred nanopatterns on the tape surface but maintain the same composition,thus also acting as functional nanophotonic structures.Using tape nanolithography,we demonstrate several tapesupported plasmonic,dielectric,and metallo-dielectric nanostructures,as well as several devices such as refractive index sensors,conformable plasmonic surfaces,and Fabry-Perot cavity resonators.Further,we demonstrate tape nanolithography-assisted manufacturing of a standalone plasmonic nanohole film and its transfer to unconventional substrates such as a cleaved facet and the curved side of an optical fiber.
基金Project supported by the National Natural Science Foundation of China.
文摘Blue electroluminescence of diamond thin film has already been investigated by some authors. To our knowledge, ultraviolet electroluminescence of diamond thin film has not been reported so far. We have prepared an electroluminescence device with
文摘We have investigated the 20 nm p-type double gate junctionless tunnel field effect transistor （P-DGJLTFET） and the impact of variation of different device parameters on the performance parameters of the P-DGJLTFET is discussed. We achieved excellent results of different performance parameters by taking the optimized device parameters of the P-DGJLTFET. Together with a high-k dielectric material （TiO2） of 20 nm gate length, the simulation results of the P-DGJLTFET show excellent characteristics with a high IoN of ～ 0.3 mA/μm, a low/OFF of ～ 30 fA/μm, a high ION/IOFF ratio of ～ 1×10^10, a subthreshold slope （SS） point of ～ 23 mV/decade, and an average SS of ～ 49 mV/decade at a supply voltage of -1 V and at room temperature, which indicates that PDGJLTFET is a promising candidate for sub-22 nm technology nodes in the implementation of integrated circuits.
