Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and nanoelectrodes.In this paper,we present a ...Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and nanoelectrodes.In this paper,we present a novel fabrication method for graphene nanoeletrodes with nanogap.First,graphene grown by chemical vapor deposition(CVD)is assembled to a chip with microelectrodes.Second,an atomic force microscopy(AFM)based mechanical cutting method is developed to cut the graphene into nanoribbons and nanoeletrodes with nanogap.Then the electronic property of a single nanodot is characterized using the garphene nanoelectrodes,demonstrating the effectiveness of the graphene nanoelectrodes.The fabricated graphene nanoeletrode pairs can be used as probes to detect single molecule in micro-environment,and show an attractive prospect for future molecular electronics applications.展开更多
Uniform silver-containing metal nanostructures with well-defined nanogaps hold great promise for ultrasensitive surface-enhanced Raman scattering （SERS） analyses. Nevertheless, the direct synthesis of such nanostruc...Uniform silver-containing metal nanostructures with well-defined nanogaps hold great promise for ultrasensitive surface-enhanced Raman scattering （SERS） analyses. Nevertheless, the direct synthesis of such nanostructures with strong and stable SERS signals remains extremely challenging. Here, we report a DNA-mediated approach for the direct synthesis of gold-silver nano-mushrooms with interior nanogaps. The SERS intensities of these nano-mushrooms were critically dependent on the area of the nanogap between the gold head and the silver cap. We found that the formation of nanogaps was finely tunable by controlling the surface density of 6-carboxy-X-rhodamine （ROX） labeled single-stranded DNA （ssDNA） on the gold nanoparticles. We obtained nano-mushrooms in high yield with a high SERS signal enhancement factor of -1.0×109, much higher than that for Au-Ag nanostructures without nanogaps. Measurements for single nano- mushrooms show that these structures have both sensitive and reproducible SERS signals.展开更多
A lithography-independent and wafer scale method to fabricate a metal nanogap structure is demonstrated. Polysilicon was first dry etched using photoresist （PR） as the etch mask patterned by photolithography. Then, ...A lithography-independent and wafer scale method to fabricate a metal nanogap structure is demonstrated. Polysilicon was first dry etched using photoresist （PR） as the etch mask patterned by photolithography. Then, by depositing conformal SiO2 on the polysilicon pattern, etching back SiO2 anisotropically in the perpendicular direction and removing the polysilicon with KOH, a sacrificial SiO2 spacer was obtained. Finally, after metal evaporation and lifting-off of the SiO2 spacer, an 82 nm metal-gap structure was achieved. The size of the nanogap is not determined by the photolithography, but by the thickness of the SiO2. The method reported in this paper is compatible with modern semiconductor technology and can be used in mass production.展开更多
By wiring molecules into circuits, ＂molecular electronics＂ aims at studying electronic properties of single molecules and their ensembles, on this basis exploiting their intrinsic functionalities, and eventually app...By wiring molecules into circuits, ＂molecular electronics＂ aims at studying electronic properties of single molecules and their ensembles, on this basis exploiting their intrinsic functionalities, and eventually applying them as building blocks of electronic components for future electronic devices. Herein, fabricating reliable solid-state molecular devices and developing synthetic molecules endowed with desirable electronic properties, have been two major tasks since the dawn of molecular electronics. This review focuses on recent advances and efforts regarding the main challenges in this field, highlighting fabrication of nanogap electrodes for single-molecule junctions, and self-assembled-monolayers （SAMs） for functional devices. The prospect of molecular-scale electronics is also discussed.展开更多
We describe the fabrication of metal nanogaps of sub-20nm in feature size using the proximity effect in electron beam lithography （EBL）. The proximity effect is extended to develop a flexible and practical method fo...We describe the fabrication of metal nanogaps of sub-20nm in feature size using the proximity effect in electron beam lithography （EBL）. The proximity effect is extended to develop a flexible and practical method for preparing metal （e. g. Au or Ag） nanogaps and arrays in combination with a transfer process （e. g., deposition/lift-off）. Different from the direct gap-writing process,the nanogap precursor structures （nanoconnections） were designed by GDSII software and then written by electron beam. Following a deposition and lift-off process, the metal nanogaps were obtained and the nanogap size can be lowered to -10nm by controlling the exposure dose in EBL.展开更多
Nanogap electrodes consist of pairs of electrically conducting tips that exhibit nanoscale gaps.They are building blocks for a variety of applications in quantum electronics,nanophotonics,plasmonics,nanopore sequencin...Nanogap electrodes consist of pairs of electrically conducting tips that exhibit nanoscale gaps.They are building blocks for a variety of applications in quantum electronics,nanophotonics,plasmonics,nanopore sequencing,molecular electronics,and molecular sensing.Crack-junctions(CJs)constitute a new class of nanogap electrodes that are formed by controlled fracture of suspended bridge structures fabricated in an electrically conducting thin film under residual tensile stress.Key advantages of the CJ methodology over alternative technologies are that CJs can be fabricated with wafer-scale processes,and that the width of each individual nanogap can be precisely controlled in a range from o2 to 4100 nm.While the realization of CJs has been demonstrated in initial experiments,the impact of the different design parameters on the resulting CJs has not yet been studied.Here we investigate the influence of design parameters such as the dimensions and shape of the notches,the length of the electrode-bridge and the design of the anchors,on the formation and propagation of cracks and on the resulting features of the CJs.We verify that the design criteria yields accurate prediction of crack formation in electrode-bridges featuring a beam width of 280 nm and beam lengths ranging from 1 to 1.8μm.We further present design as well as experimental guidelines for the fabrication of CJs and propose an approach to initiate crack formation after release etching of the suspended electrode-bridge,thereby enabling the realization of CJs with pristine electrode surfaces.展开更多
In ion-annihilation electrochemiluminescence(ECL),luminophore ions are generated by oxidation as well as reduction at electrodes surfaces,and subsequently recombine into an electronically excited state,which emits lig...In ion-annihilation electrochemiluminescence(ECL),luminophore ions are generated by oxidation as well as reduction at electrodes surfaces,and subsequently recombine into an electronically excited state,which emits light.The intensity of the emitted light is often limited by the kinetic rate of recombination of the luminophore ion species.Recombination or annihilation rates are high ranging up to approximately 10^(10) M^(−1) s^(−1) and can be difficult to determine using scanning electrochemical microscopy or high-frequency oscillations of an electrode potential.Here,we propose determining annihilation kinetics by measuring the relative change of the emitted light intensity as a function of luminophore concentration.Using finite element simulations of annihilation ECL in a geometry of two closely spaced electrodes biased at constant potentials,we show that,with increasing concentrations,luminescence intensity crosses over from a quadratic dependence on concentration to a linear regime-depending on the rate of annihilation.Our numerical results are applicable to scanning electrochemical microscopy as well as nanofluidic electrochemical devices to determine fast ion-annihilation kinetics.展开更多
Here we demonstrate the fabrication of nanometer-sized gaps by assembling single coreshell nanoparticles between metallic nanoelectrodes. Protein coated SiO2@Au coreshell nanopar- tides arc synthesized and positioned ...Here we demonstrate the fabrication of nanometer-sized gaps by assembling single coreshell nanoparticles between metallic nanoelectrodes. Protein coated SiO2@Au coreshell nanopar- tides arc synthesized and positioned between fluorescent molecules-covered electrodes in a controllable way using dielectrophoretic trapping, forming nanogaps sandwiched between nanoparticle and manoelectrodes. Preliminary photoluminescence measurements show that enhanced molecular fluorescence could be detected from the fluorescent molecules inside the nanogaps. These results pave the way for realizing electrically driven molecular fluorescence based on nanogap electrodes.展开更多
We used scattering-type scanning near-field optical microscopy(s-SNOM)to investigate the plasmonic properties of edges in well-defined graphene nanostructures,including sharp tapers,nanoribbons and nanogaps,which were...We used scattering-type scanning near-field optical microscopy(s-SNOM)to investigate the plasmonic properties of edges in well-defined graphene nanostructures,including sharp tapers,nanoribbons and nanogaps,which were all fabricated via the growth-etching chemical vapor deposition(GECVD)method.The obtained near-field images revealed the localized plasmon modes along the graphene nanoribbon;these modes strongly depended on the size of the graphene pattern,the angle of the tapered graphene and the infrared excitation wavelength.These interesting plasmon modes were verified by numerical simulations and explained by the reflection,and interference of electromagnetic waves at the graphene–SiO_(2) edge.The constructive interference at the graphene nanogap caused by charge accumulation was demonstrated for the first time.Using the infrared nanoimaging technique,greater plasmon broadening was observed in the zigzag edge than in the armchair edge.Our study suggests that graphene edges should be separated by an effective working distance to avoid the overlapping of localized plasmon modes,which is very important for the design of graphene-based plasmonic circuits and devices.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61106109,61304251)the CAS/SAFEA Internaional Partnership Program for Creative Research Teams
文摘Graphene has the advantages of high electrical conductivity,high heat conductivity,and low noise,which makes it a potential option for integrated circuits interconnection and nanoelectrodes.In this paper,we present a novel fabrication method for graphene nanoeletrodes with nanogap.First,graphene grown by chemical vapor deposition(CVD)is assembled to a chip with microelectrodes.Second,an atomic force microscopy(AFM)based mechanical cutting method is developed to cut the graphene into nanoribbons and nanoeletrodes with nanogap.Then the electronic property of a single nanodot is characterized using the garphene nanoelectrodes,demonstrating the effectiveness of the graphene nanoelectrodes.The fabricated graphene nanoeletrode pairs can be used as probes to detect single molecule in micro-environment,and show an attractive prospect for future molecular electronics applications.
基金We thank the National Basic Research Program of China （973 program） （Nos. 2013CB932802 and 2012CB932600）,Alexander von Humboldt Foundation, and the National Natural Science Foundation of China （Nos. 91127037 and 91123037） for financial support.
文摘Uniform silver-containing metal nanostructures with well-defined nanogaps hold great promise for ultrasensitive surface-enhanced Raman scattering （SERS） analyses. Nevertheless, the direct synthesis of such nanostructures with strong and stable SERS signals remains extremely challenging. Here, we report a DNA-mediated approach for the direct synthesis of gold-silver nano-mushrooms with interior nanogaps. The SERS intensities of these nano-mushrooms were critically dependent on the area of the nanogap between the gold head and the silver cap. We found that the formation of nanogaps was finely tunable by controlling the surface density of 6-carboxy-X-rhodamine （ROX） labeled single-stranded DNA （ssDNA） on the gold nanoparticles. We obtained nano-mushrooms in high yield with a high SERS signal enhancement factor of -1.0×109, much higher than that for Au-Ag nanostructures without nanogaps. Measurements for single nano- mushrooms show that these structures have both sensitive and reproducible SERS signals.
基金Project supported by the National High-Tech Research and Development Program of China (No.2008AA031402)
文摘A lithography-independent and wafer scale method to fabricate a metal nanogap structure is demonstrated. Polysilicon was first dry etched using photoresist （PR） as the etch mask patterned by photolithography. Then, by depositing conformal SiO2 on the polysilicon pattern, etching back SiO2 anisotropically in the perpendicular direction and removing the polysilicon with KOH, a sacrificial SiO2 spacer was obtained. Finally, after metal evaporation and lifting-off of the SiO2 spacer, an 82 nm metal-gap structure was achieved. The size of the nanogap is not determined by the photolithography, but by the thickness of the SiO2. The method reported in this paper is compatible with modern semiconductor technology and can be used in mass production.
基金support from the National Natural Science Foundation of China (No. 51673114)Shanghai Science and Technology Committee (No. 17ZR1447300)Basic Research Development Programme (No. 2017YFA0207500)
文摘By wiring molecules into circuits, ＂molecular electronics＂ aims at studying electronic properties of single molecules and their ensembles, on this basis exploiting their intrinsic functionalities, and eventually applying them as building blocks of electronic components for future electronic devices. Herein, fabricating reliable solid-state molecular devices and developing synthetic molecules endowed with desirable electronic properties, have been two major tasks since the dawn of molecular electronics. This review focuses on recent advances and efforts regarding the main challenges in this field, highlighting fabrication of nanogap electrodes for single-molecule junctions, and self-assembled-monolayers （SAMs） for functional devices. The prospect of molecular-scale electronics is also discussed.
基金the National Natural Science Foundation of China(No.20704042)the Shanghai Pujiang Talent Plan(No.07PJ14095)+1 种基金the CAS Knowledge Innovation Programthe Committee of Science and Technology of Shanghai(Nos.06XD14020,07JC14058,0752nm016)~~
文摘We describe the fabrication of metal nanogaps of sub-20nm in feature size using the proximity effect in electron beam lithography （EBL）. The proximity effect is extended to develop a flexible and practical method for preparing metal （e. g. Au or Ag） nanogaps and arrays in combination with a transfer process （e. g., deposition/lift-off）. Different from the direct gap-writing process,the nanogap precursor structures （nanoconnections） were designed by GDSII software and then written by electron beam. Following a deposition and lift-off process, the metal nanogaps were obtained and the nanogap size can be lowered to -10nm by controlling the exposure dose in EBL.
基金The work was supported by the European Research Council through the ERC Advanced Grant xMEMs(No.267528)the ERC Starting Grant M&M’s(No.277879).
文摘Nanogap electrodes consist of pairs of electrically conducting tips that exhibit nanoscale gaps.They are building blocks for a variety of applications in quantum electronics,nanophotonics,plasmonics,nanopore sequencing,molecular electronics,and molecular sensing.Crack-junctions(CJs)constitute a new class of nanogap electrodes that are formed by controlled fracture of suspended bridge structures fabricated in an electrically conducting thin film under residual tensile stress.Key advantages of the CJ methodology over alternative technologies are that CJs can be fabricated with wafer-scale processes,and that the width of each individual nanogap can be precisely controlled in a range from o2 to 4100 nm.While the realization of CJs has been demonstrated in initial experiments,the impact of the different design parameters on the resulting CJs has not yet been studied.Here we investigate the influence of design parameters such as the dimensions and shape of the notches,the length of the electrode-bridge and the design of the anchors,on the formation and propagation of cracks and on the resulting features of the CJs.We verify that the design criteria yields accurate prediction of crack formation in electrode-bridges featuring a beam width of 280 nm and beam lengths ranging from 1 to 1.8μm.We further present design as well as experimental guidelines for the fabrication of CJs and propose an approach to initiate crack formation after release etching of the suspended electrode-bridge,thereby enabling the realization of CJs with pristine electrode surfaces.
文摘In ion-annihilation electrochemiluminescence(ECL),luminophore ions are generated by oxidation as well as reduction at electrodes surfaces,and subsequently recombine into an electronically excited state,which emits light.The intensity of the emitted light is often limited by the kinetic rate of recombination of the luminophore ion species.Recombination or annihilation rates are high ranging up to approximately 10^(10) M^(−1) s^(−1) and can be difficult to determine using scanning electrochemical microscopy or high-frequency oscillations of an electrode potential.Here,we propose determining annihilation kinetics by measuring the relative change of the emitted light intensity as a function of luminophore concentration.Using finite element simulations of annihilation ECL in a geometry of two closely spaced electrodes biased at constant potentials,we show that,with increasing concentrations,luminescence intensity crosses over from a quadratic dependence on concentration to a linear regime-depending on the rate of annihilation.Our numerical results are applicable to scanning electrochemical microscopy as well as nanofluidic electrochemical devices to determine fast ion-annihilation kinetics.
文摘Here we demonstrate the fabrication of nanometer-sized gaps by assembling single coreshell nanoparticles between metallic nanoelectrodes. Protein coated SiO2@Au coreshell nanopar- tides arc synthesized and positioned between fluorescent molecules-covered electrodes in a controllable way using dielectrophoretic trapping, forming nanogaps sandwiched between nanoparticle and manoelectrodes. Preliminary photoluminescence measurements show that enhanced molecular fluorescence could be detected from the fluorescent molecules inside the nanogaps. These results pave the way for realizing electrically driven molecular fluorescence based on nanogap electrodes.
基金support from the National Key Research&Development Program(2015CB932700 and 2016YFA0201902)the National Natural Science Foundation of China(grant No.51290273,91433107,51325205 and 51521091)+6 种基金the Doctoral Fund of the Ministry of Education of China(grant No.20123201120026)ARC(DP140101501 and FT150100450)the Collaborative Innovation Center of Suzhou Nano Science&Technologythe Priority Academic Program Development of Jiangsu Higher Education InstitutionsA*STAR Pharos Programme(grant No.1527000014,with Project No.R-263-000-B91-305)Competitive Research Program(CRP Award No.NRF-CRP15-2015-03)the National Research Foundation,Prime Minister’s Office,Singapore。
文摘We used scattering-type scanning near-field optical microscopy(s-SNOM)to investigate the plasmonic properties of edges in well-defined graphene nanostructures,including sharp tapers,nanoribbons and nanogaps,which were all fabricated via the growth-etching chemical vapor deposition(GECVD)method.The obtained near-field images revealed the localized plasmon modes along the graphene nanoribbon;these modes strongly depended on the size of the graphene pattern,the angle of the tapered graphene and the infrared excitation wavelength.These interesting plasmon modes were verified by numerical simulations and explained by the reflection,and interference of electromagnetic waves at the graphene–SiO_(2) edge.The constructive interference at the graphene nanogap caused by charge accumulation was demonstrated for the first time.Using the infrared nanoimaging technique,greater plasmon broadening was observed in the zigzag edge than in the armchair edge.Our study suggests that graphene edges should be separated by an effective working distance to avoid the overlapping of localized plasmon modes,which is very important for the design of graphene-based plasmonic circuits and devices.
