Nanowires （NWs） are ideal nanostructures for exploring the effects of low dimensionality and thermal conductivity suppression on thermoelectric behavior. However, it is challenging to accurately measure temperature ...Nanowires （NWs） are ideal nanostructures for exploring the effects of low dimensionality and thermal conductivity suppression on thermoelectric behavior. However, it is challenging to accurately measure temperature gradients and heat flow in such systems. Here, using a combination of spatially resolved Raman spectroscopy and transport measurements, we determine all the thermoelectric properties of single Se-doped InSb NWs and quantify the figure of merit ZT. The measured laser-induced heating in the NWs and associated electrical response are well described by a 1D heat equation model. Our method allows the determination of the thermal contact resistances at the source and drain electrodes of the NW, which are negligible in our system. The measured thermoelectric parameters of InSb NWs agree well with those obtained based on field-effect transistor Seebeck measurements.展开更多
The controlled tailoring of the energy distribution in an electron system opens the way to interesting new physics and device concepts, as demonstrated by research on metallic nanodevices during recent years. Here we ...The controlled tailoring of the energy distribution in an electron system opens the way to interesting new physics and device concepts, as demonstrated by research on metallic nanodevices during recent years. Here we investigate how Josephson coupling in a superconductor-InAs nanowire junction can be tuned by means of hot-electron injection and we show that a complete suppression of superconductive effects can be achieved using a power as low as 100 pW. Nanowires offer a novel design freedom as they allow axial and radial heterostructures to be defined as well as control over doping profiles, which can be crucial in the development of devices--such as nanorefrigerators--where precisely controlled and predictable energy barriers are mandatory. Our work provides estimates for unknown key thermal and electrical parameters, such as the electron-phonon coupling, in our InAs nanostructures.展开更多
We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel character...We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel characteristics with a current suppression by 〉4 orders of magnitude for a junction bias well below the A1 gap of △0≈ 200 μeV. The experimental data agree well with the Bardeen- Cooper-Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δT = 10 mK is achieved at a bath temperature of Tbath≈ 250-350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.展开更多
Crystal-phase low-dimensional structures offer great potential for the implementation of photonic devices of interest for quantum information processing.In this context,unveiling the fundamental parameters of the crys...Crystal-phase low-dimensional structures offer great potential for the implementation of photonic devices of interest for quantum information processing.In this context,unveiling the fundamental parameters of the crystal phase structure is of much relevance for several applications.Here,we report on the anisotropy of the g-factor tensor and diamagnetic coefficient in wurtzite/zincblende(WZ/ZB)crystal-phase quantum dots(QDs)realized in single InP nanowires.The WZ and ZB alternating axial sections in the NWs are identified by high-angle annular dark-field scanning transmission electron microscopy.The electron(hole)g-factor tensor and the exciton diamagnetic coefficients in WZ/ZB crystal-phase QDs are determined through micro-photoluminescence measurements at low temperature(4.2 K)with different magnetic field configurations,and rationalized by invoking the spin-correlated orbital current model.Our work provides key parameters for band gap engineering and spin states control in crystal-phase low-dimensional structures in nanowires.展开更多
We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients...We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated greatly exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device.展开更多
Semiconductor nanowire field-effect transistors represent a promising platform for the development of roomtemperature(RT)terahertz(THz)frequency light detectors due to the strong nonlinearity of their transfer charact...Semiconductor nanowire field-effect transistors represent a promising platform for the development of roomtemperature(RT)terahertz(THz)frequency light detectors due to the strong nonlinearity of their transfer characteristics and their remarkable combination of low noise-equivalent powers(<1 nW Hz^(−1/2))and high responsivities(>100 V/W).Nano-engineering an NW photodetector combining high sensitivity with high speed(subns)in the THz regime at RT is highly desirable for many frontier applications in quantum optics and nanophotonics,but this requires a clear understanding of the origin of the photo-response.Conventional electrical and optical measurements,however,cannot unambiguously determine the dominant detection mechanism due to inherent device asymmetry that allows different processes to be simultaneously activated.Here,we innovatively capture snapshots of the photo-response of individual InAs nanowires via high spatial resolution(35 nm)THz photocurrent nanoscopy.By coupling a THz quantum cascade laser to scattering-type scanning near-field optical microscopy(s-SNOM)and monitoring both electrical and optical readouts,we simultaneously measure transport and scattering properties.The spatially resolved electric response provides unambiguous signatures of photo-thermoelectric and bolometric currents whose interplay is discussed as a function of photon density and material doping,therefore providing a route to engineer photo-responses by design.展开更多
We investigate the tunnel coupling between the outer p-type GaAsSb shell and the n-type InAs core in catalyst-free InAs/lnP/GaAsSb core-dualshell nanowires.We present a device fabrication protocol based on wet-etching...We investigate the tunnel coupling between the outer p-type GaAsSb shell and the n-type InAs core in catalyst-free InAs/lnP/GaAsSb core-dualshell nanowires.We present a device fabrication protocol based on wet-etching processes on selected areas of the nanostructures that enables multiple configurations of measurements in the same nanowire-based device(i.e.shell-shell,core-core and core-shell).Low-temperature(4.2 K)transport in the shell-shell configuration in nanowires with 5 nm-thick InP barrier reveals a weak negative differential resistance.Differently,when the InP barrier thickness is increased to 10 nm,this negative differential resistance is fully quenched.The electrical resistance between the InAs core and the GaAsSb shell,measured in core-shell configuration,is significantly higher with respect to the resistance of the InAs core and of the GaAsSb shell.The field effect,applied via a back-gate,has an opposite impact on the electrical transport in the core and in the shell portions.Our results show that electron and hole free carriers populate the InAs and GaAsSb regions respectively and indicate InAs/InP/GaAsSb core-dualshell nanowires as an ideal system for the investigation of the physics of interacting electrons and holes at the nanoscale.展开更多
The origin of the anomalous transport feature appearing at a conductance G 0.7× （2e2/h） in quasi-lD ballistic devices-the so-called 0.7 anomaly-represents a long standing puzzle. Several mechanisms have been pr...The origin of the anomalous transport feature appearing at a conductance G 0.7× （2e2/h） in quasi-lD ballistic devices-the so-called 0.7 anomaly-represents a long standing puzzle. Several mechanisms have been proposed to explain it, but a general consensus has not been achieved. Proposed explanations have been based on quantum interference, the Kondo effect, Wigner crystallization, and other phenomena. A key open issue is whether the point defects that can occur in these low-dimensional devices are the physical cause behind this conductance anomaly. Here we adopt a scanning gate microscopy technique to map individual impurity positions in several quasi-lD constrictions and correlate these with conductance characteristics. Our data demonstrate that the 0.7 anomaly can be observed irrespective of the presence of localized defects, and we conclude that the 0.7 anomaly is a fundamental property of low-dimensional systems.展开更多
文摘Nanowires （NWs） are ideal nanostructures for exploring the effects of low dimensionality and thermal conductivity suppression on thermoelectric behavior. However, it is challenging to accurately measure temperature gradients and heat flow in such systems. Here, using a combination of spatially resolved Raman spectroscopy and transport measurements, we determine all the thermoelectric properties of single Se-doped InSb NWs and quantify the figure of merit ZT. The measured laser-induced heating in the NWs and associated electrical response are well described by a 1D heat equation model. Our method allows the determination of the thermal contact resistances at the source and drain electrodes of the NW, which are negligible in our system. The measured thermoelectric parameters of InSb NWs agree well with those obtained based on field-effect transistor Seebeck measurements.
文摘The controlled tailoring of the energy distribution in an electron system opens the way to interesting new physics and device concepts, as demonstrated by research on metallic nanodevices during recent years. Here we investigate how Josephson coupling in a superconductor-InAs nanowire junction can be tuned by means of hot-electron injection and we show that a complete suppression of superconductive effects can be achieved using a power as low as 100 pW. Nanowires offer a novel design freedom as they allow axial and radial heterostructures to be defined as well as control over doping profiles, which can be crucial in the development of devices--such as nanorefrigerators--where precisely controlled and predictable energy barriers are mandatory. Our work provides estimates for unknown key thermal and electrical parameters, such as the electron-phonon coupling, in our InAs nanostructures.
文摘We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel characteristics with a current suppression by 〉4 orders of magnitude for a junction bias well below the A1 gap of △0≈ 200 μeV. The experimental data agree well with the Bardeen- Cooper-Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δT = 10 mK is achieved at a bath temperature of Tbath≈ 250-350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.
基金This work was supported by the National Natural Science Foundation of China(Nos.11934019,61675228,11721404,51761145104,and 11874419)the Strategic Priority Research Program,the Instrument Developing Project and the Interdisciplinary Innovation Team of the Chinese Academy of Sciences(Nos.XDB28000000 and YJKYYQ20180036)+2 种基金the Key RD Program of Guangdong Province(No.2018B030329001)the Key Laboratory Fund(No.614280303051701)We acknowledge financial support from the SUPERTOP project,QUANTERA ERA-NET Cofund in Quantum Technologies.
文摘Crystal-phase low-dimensional structures offer great potential for the implementation of photonic devices of interest for quantum information processing.In this context,unveiling the fundamental parameters of the crystal phase structure is of much relevance for several applications.Here,we report on the anisotropy of the g-factor tensor and diamagnetic coefficient in wurtzite/zincblende(WZ/ZB)crystal-phase quantum dots(QDs)realized in single InP nanowires.The WZ and ZB alternating axial sections in the NWs are identified by high-angle annular dark-field scanning transmission electron microscopy.The electron(hole)g-factor tensor and the exciton diamagnetic coefficients in WZ/ZB crystal-phase QDs are determined through micro-photoluminescence measurements at low temperature(4.2 K)with different magnetic field configurations,and rationalized by invoking the spin-correlated orbital current model.Our work provides key parameters for band gap engineering and spin states control in crystal-phase low-dimensional structures in nanowires.
文摘We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated greatly exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device.
基金supported by the European Research Council through the ERC Consolidator Grant(681379)SPRINTby the European Union through the H2020-MSCA-ITN-2017+2 种基金TeraApps(765426)grantpartially by the SUPERTOP project of the QuantERA ERA-NET Cofund in Quantum Technologies and by the FET-OPEN projectpartial support from the second half of the Balzan Prize 2016 in applied photonics delivered to Federico Capasso.
文摘Semiconductor nanowire field-effect transistors represent a promising platform for the development of roomtemperature(RT)terahertz(THz)frequency light detectors due to the strong nonlinearity of their transfer characteristics and their remarkable combination of low noise-equivalent powers(<1 nW Hz^(−1/2))and high responsivities(>100 V/W).Nano-engineering an NW photodetector combining high sensitivity with high speed(subns)in the THz regime at RT is highly desirable for many frontier applications in quantum optics and nanophotonics,but this requires a clear understanding of the origin of the photo-response.Conventional electrical and optical measurements,however,cannot unambiguously determine the dominant detection mechanism due to inherent device asymmetry that allows different processes to be simultaneously activated.Here,we innovatively capture snapshots of the photo-response of individual InAs nanowires via high spatial resolution(35 nm)THz photocurrent nanoscopy.By coupling a THz quantum cascade laser to scattering-type scanning near-field optical microscopy(s-SNOM)and monitoring both electrical and optical readouts,we simultaneously measure transport and scattering properties.The spatially resolved electric response provides unambiguous signatures of photo-thermoelectric and bolometric currents whose interplay is discussed as a function of photon density and material doping,therefore providing a route to engineer photo-responses by design.
基金This research activity was partially supported by the SUPERTOP project,QUANTERA ERA-NET Cofound in Quantum Technologies,and by the FET-OPEN project AndQC.
文摘We investigate the tunnel coupling between the outer p-type GaAsSb shell and the n-type InAs core in catalyst-free InAs/lnP/GaAsSb core-dualshell nanowires.We present a device fabrication protocol based on wet-etching processes on selected areas of the nanostructures that enables multiple configurations of measurements in the same nanowire-based device(i.e.shell-shell,core-core and core-shell).Low-temperature(4.2 K)transport in the shell-shell configuration in nanowires with 5 nm-thick InP barrier reveals a weak negative differential resistance.Differently,when the InP barrier thickness is increased to 10 nm,this negative differential resistance is fully quenched.The electrical resistance between the InAs core and the GaAsSb shell,measured in core-shell configuration,is significantly higher with respect to the resistance of the InAs core and of the GaAsSb shell.The field effect,applied via a back-gate,has an opposite impact on the electrical transport in the core and in the shell portions.Our results show that electron and hole free carriers populate the InAs and GaAsSb regions respectively and indicate InAs/InP/GaAsSb core-dualshell nanowires as an ideal system for the investigation of the physics of interacting electrons and holes at the nanoscale.
基金This work was supported by the Italian Ministry of Research （Ministero dell＇Istruzione, dell＇Universitae della Ricerca （MIUR）-Fondo per gli Investimenti della Ricerca di Base （FIRB） project No. RBID08B3FM） and by the Italian Ministry of Foreign Affairs （Ministero degli Affari Esteri, Direzione Generale per la Promozione del Sistema Paese, progetto： Nanoelettronica quantistica per le tecnologie delle informazioni）. Two of us （C.R. and W.W.） thank the Swiss National Science Foundation （SNSF） financial support.
文摘The origin of the anomalous transport feature appearing at a conductance G 0.7× （2e2/h） in quasi-lD ballistic devices-the so-called 0.7 anomaly-represents a long standing puzzle. Several mechanisms have been proposed to explain it, but a general consensus has not been achieved. Proposed explanations have been based on quantum interference, the Kondo effect, Wigner crystallization, and other phenomena. A key open issue is whether the point defects that can occur in these low-dimensional devices are the physical cause behind this conductance anomaly. Here we adopt a scanning gate microscopy technique to map individual impurity positions in several quasi-lD constrictions and correlate these with conductance characteristics. Our data demonstrate that the 0.7 anomaly can be observed irrespective of the presence of localized defects, and we conclude that the 0.7 anomaly is a fundamental property of low-dimensional systems.
