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Tadokoro Y, Funayama K, Kawano K, Miura A, Hirotani J, Ohno Y, Tanaka H. Artificial-intelligence-assisted mass fabrication of nanocantilevers from randomly positioned single carbon nanotubes. MICROSYSTEMS & NANOENGINEERING 2023; 9:32. [PMID: 36969967 PMCID: PMC10033894 DOI: 10.1038/s41378-023-00507-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 01/22/2023] [Accepted: 02/08/2023] [Indexed: 06/18/2023]
Abstract
Nanoscale cantilevers (nanocantilevers) made from carbon nanotubes (CNTs) provide tremendous benefits in sensing and electromagnetic applications. This nanoscale structure is generally fabricated using chemical vapor deposition and/or dielectrophoresis, which contain manual, time-consuming processes such as the placing of additional electrodes and careful observation of single-grown CNTs. Here, we demonstrate a simple and Artificial Intelligence (AI)-assisted method for the efficient fabrication of a massive CNT-based nanocantilever. We used randomly positioned single CNTs on the substrate. The trained deep neural network recognizes the CNTs, measures their positions, and determines the edge of the CNT on which an electrode should be clamped to form a nanocantilever. Our experiments demonstrate that the recognition and measurement processes are automatically completed in 2 s, whereas comparable manual processing requires 12 h. Notwithstanding the small measurement error by the trained network (within 200 nm for 90% of the recognized CNTs), more than 34 nanocantilevers were successfully fabricated in one process. Such high accuracy contributes to the development of a massive field emitter using the CNT-based nanocantilever, in which the output current is obtained with a low applied voltage. We further showed the benefit of fabricating massive CNT-nanocantilever-based field emitters for neuromorphic computing. The activation function, which is a key function in a neural network, was physically realized using an individual CNT-based field emitter. The introduced neural network with the CNT-based field emitters recognized handwritten images successfully. We believe that our method can accelerate the research and development of CNT-based nanocantilevers for realizing promising future applications.
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Affiliation(s)
- Yukihiro Tadokoro
- Toyota Central R&D Labs., Inc., Nagakute, Aichi Japan
- Toyota Research Institute of North America, Ann Arbor, MI USA
| | | | | | - Atsushi Miura
- Toyota Central R&D Labs., Inc., Nagakute, Aichi Japan
| | | | | | - Hiroya Tanaka
- Toyota Central R&D Labs., Inc., Nagakute, Aichi Japan
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2
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Li X, Wei Y, Lu G, Mei Z, Zhang G, Liang L, Li Q, Fan S, Zhang Y. Gate-tunable contact-induced Fermi-level shift in semimetal. Proc Natl Acad Sci U S A 2022; 119:e2119016119. [PMID: 35452312 PMCID: PMC9169931 DOI: 10.1073/pnas.2119016119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 03/16/2022] [Indexed: 11/18/2022] Open
Abstract
Low-dimensional semimetal–semiconductor (Sm-S) van der Waals (vdW) heterostructures have shown their potentials in nanoelectronics and nano-optoelectronics recently. It is an important scientific issue to study the interfacial charge transfer as well as the corresponding Fermi-level shift in Sm-S systems. Here we investigated the gate-tunable contact-induced Fermi-level shift (CIFS) behavior in a semimetal single-walled carbon nanotube (SWCNT) that formed a heterojunction with a transition-metal dichalcogenide (TMD) flake. A resistivity comparison methodology and a Fermi-level catch-up model have been developed to measure and analyze the CIFS, whose value is determined by the resistivity difference between the naked SWCNT segment and the segment in contact with the TMD. Moreover, the relative Fermi-level positions of SWCNT and two-dimensional (2D) semiconductors can be efficiently reflected by the gate-tunable resistivity difference. The work function change of the semimetal, as a result of CIFS, will naturally introduce a modified form of the Schottky–Mott rule, so that a modified Schottky barrier height can be obtained for the Sm-S junction. The methodology and physical model should be useful for low-dimensional reconfigurable nanodevices based on Sm-S building blocks.
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Affiliation(s)
- Xuanzhang Li
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Yang Wei
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Gaotian Lu
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Zhen Mei
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Guangqi Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Liang Liang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Qunqing Li
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Shoushan Fan
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
| | - Yuegang Zhang
- State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084, China
- Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084, China
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3
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Lotfizadeh N, Senger MJ, McCulley DR, Minot ED, Deshpande VV. Quantum Interferences in Ultraclean Carbon Nanotubes. PHYSICAL REVIEW LETTERS 2021; 126:216802. [PMID: 34114831 DOI: 10.1103/physrevlett.126.216802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 04/15/2021] [Indexed: 06/12/2023]
Abstract
Electronic analogs of optical interferences are powerful tools to investigate quantum phenomena in condensed matter. In carbon nanotubes (CNTs), it is well established that an electronic Fabry-Perot interferometer can be realized. Other types of quantum interferences should also arise in CNTs, but have proven challenging to realize. In particular, CNTs have been identified as a system to realize the electronic analog of a Sagnac interferometer-the most sensitive optical interferometer. To realize this Sagnac effect, interference between nonidentical transmission channels in a single CNT must be observed. Here, we use suspended, ultraclean CNTs of known chiral index to study both Fabry-Perot and Sagnac electron interferences. We verify theoretical predictions for the behavior of Sagnac oscillations and the persistence of the Sagnac oscillations at high temperatures. As suggested by existing theoretical studies, our results show that these quantum interferences may be used for electronic structure characterization of carbon nanotubes and the study of many-body effects in these model one-dimensional systems.
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Affiliation(s)
- Neda Lotfizadeh
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
| | - Mitchell J Senger
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Daniel R McCulley
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Ethan D Minot
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Vikram V Deshpande
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA
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4
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Margańska M, Schmid DR, Dirnaichner A, Stiller PL, Strunk C, Grifoni M, Hüttel AK. Shaping Electron Wave Functions in a Carbon Nanotube with a Parallel Magnetic Field. PHYSICAL REVIEW LETTERS 2019; 122:086802. [PMID: 30932614 DOI: 10.1103/physrevlett.122.086802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 01/25/2019] [Indexed: 06/09/2023]
Abstract
A magnetic field, through its vector potential, usually causes measurable changes in the electron wave function only in the direction transverse to the field. Here, we demonstrate experimentally and theoretically that, in carbon nanotube quantum dots combining cylindrical topology and bipartite hexagonal lattice, a magnetic field along the nanotube axis impacts also the longitudinal profile of the electronic states. With the high (up to 17 T) magnetic fields in our experiment, the wave functions can be tuned all the way from a "half-wave resonator" shape with nodes at both ends to a "quarter-wave resonator" shape with an antinode at one end. This in turn causes a distinct dependence of the conductance on the magnetic field. Our results demonstrate a new strategy for the control of wave functions using magnetic fields in quantum systems with a nontrivial lattice and topology.
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Affiliation(s)
- M Margańska
- Institute for Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
| | - D R Schmid
- Institute for Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - A Dirnaichner
- Institute for Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - P L Stiller
- Institute for Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - Ch Strunk
- Institute for Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
| | - M Grifoni
- Institute for Theoretical Physics, University of Regensburg, 93053 Regensburg, Germany
| | - A K Hüttel
- Institute for Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany
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5
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Island JO, Ostermann M, Aspitarte L, Minot ED, Varsano D, Molinari E, Rontani M, Steele GA. Interaction-Driven Giant Orbital Magnetic Moments in Carbon Nanotubes. PHYSICAL REVIEW LETTERS 2018; 121:127704. [PMID: 30296145 DOI: 10.1103/physrevlett.121.127704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Indexed: 06/08/2023]
Abstract
Carbon nanotubes continue to be model systems for studies of confinement and interactions. This is particularly true in the case of so-called "ultraclean" carbon nanotube devices offering the study of quantum dots with extremely low disorder. The quality of such systems, however, has increasingly revealed glaring discrepancies between experiment and theory. Here, we address the outstanding anomaly of exceptionally large orbital magnetic moments in carbon nanotube quantum dots. We perform low temperature magnetotransport measurements of the orbital magnetic moment and find it is up to 7 times larger than expected from the conventional semiclassical model. Moreover, the magnitude of the magnetic moment monotonically drops with the addition of each electron to the quantum dot directly contradicting the widely accepted shell filling picture of single-particle levels. We carry out quasiparticle calculations, both from first principles and within the effective-mass approximation, and find the giant magnetic moments can only be captured by considering a self-energy correction to the electronic band structure due to electron-electron interactions.
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Affiliation(s)
- Joshua O Island
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - Marvin Ostermann
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
| | - Lee Aspitarte
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | - Ethan D Minot
- Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA
| | | | - Elisa Molinari
- CNR-NANO, Via Campi 213a, 41125 Modena, Italy
- Dipartimento di Scienze Fisiche, Informatiche e Matematiche (FIM), Università degli Studi di Modena e Reggio Emilia, 41125 Modena, Italy
| | | | - Gary A Steele
- Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, Netherlands
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6
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Liu S, Zhang J, Nshimiyimana JP, Chi X, Hu X, Wu P, Liu J, Wang G, Sun L. Ultraclean individual suspended single-walled carbon nanotube field effect transistor. NANOTECHNOLOGY 2018; 29:175302. [PMID: 29442999 DOI: 10.1088/1361-6528/aaaf4f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this work, we report an effective technique of fabricating ultraclean individual suspended single-walled carbon nanotube (SWNT) transistors. The surface tension of molten silver is utilized to suspend an individual SWNT between a pair of Pd electrodes during annealing treatment. This approach avoids the usage and the residues of organic resist attached to SWNTs, resulting ultraclean SWNT devices. And the resistance per micrometer of suspended SWNTs is found to be smaller than that of non-suspended SWNTs, indicating the effect of the substrate on the electrical properties of SWNTs. The ON-state resistance (∼50 kΩ), mobility of 8600 cm2 V-1 s-1 and large on/off ratio (∼105) of semiconducting suspended SWNT devices indicate its advantages and potential applications.
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Affiliation(s)
- Siyu Liu
- School of Physics and Electronics, Shandong Normal University, Jinan, 250258, People's Republic of China. CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
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7
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McRae AC, Tayari V, Porter JM, Champagne AR. Giant electron-hole transport asymmetry in ultra-short quantum transistors. Nat Commun 2017; 8:15491. [PMID: 28561024 PMCID: PMC5460015 DOI: 10.1038/ncomms15491] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 04/04/2017] [Indexed: 11/15/2022] Open
Abstract
Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e−h charging energy asymmetry). We parameterize the e−h transport asymmetry by the ratio of the hole and electron charging energies ηe−h. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, ηe−h reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV. By utilizing electron-hole asymmetry in ultra-short single-walled carbon nanotube (SWCNT) transistors, McRae et al., develop ‘two-in-one' SWCNT quantum devices that can switch from behaving as quantum-dot transistors for holes to quantum buses for electrons by changing the transistor's gate voltage
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Affiliation(s)
- A C McRae
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
| | - V Tayari
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
| | - J M Porter
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
| | - A R Champagne
- Department of Physics, Concordia University, 7141 Sherbrooke Street West, Montréal, Québec, Canada H4B 1R6
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8
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Pei T, Pályi A, Mergenthaler M, Ares N, Mavalankar A, Warner JH, Briggs GAD, Laird EA. Hyperfine and Spin-Orbit Coupling Effects on Decay of Spin-Valley States in a Carbon Nanotube. PHYSICAL REVIEW LETTERS 2017; 118:177701. [PMID: 28498696 DOI: 10.1103/physrevlett.118.177701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Indexed: 06/07/2023]
Abstract
The decay of spin-valley states is studied in a suspended carbon nanotube double quantum dot via the leakage current in Pauli blockade and via dephasing and decoherence of a qubit. From the magnetic field dependence of the leakage current, hyperfine and spin-orbit contributions to relaxation from blocked to unblocked states are identified and explained quantitatively by means of a simple model. The observed qubit dephasing rate is consistent with the hyperfine coupling strength extracted from this model and inconsistent with dephasing from charge noise. However, the qubit coherence time, although longer than previously achieved, is probably still limited by charge noise in the device.
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Affiliation(s)
- T Pei
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - A Pályi
- Department of Physics and MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, 1111 Budapest, Hungary
| | - M Mergenthaler
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - N Ares
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - A Mavalankar
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - J H Warner
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - G A D Briggs
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
| | - E A Laird
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, United Kingdom
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9
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Palii A, Aldoshin S, Tsukerblat B, Clemente-Juan JM, Gaita-Ariño A, Coronado E. Electric field controllable magnetic coupling of localized spins mediated by itinerant electrons: a toy model. Phys Chem Chem Phys 2017; 19:26098-26106. [DOI: 10.1039/c7cp03872k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
In this paper, we propose a toy model to describe the magnetic coupling between the localized spins mediated by the itinerant electron in partially delocalized mixed-valence (MV) systems.
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Affiliation(s)
- Andrew Palii
- Institute of Problems of Chemical Physics
- Chernogolovka
- Russia
- Institute of Applied Physics
- Academy of Sciences of Moldova
| | - Sergey Aldoshin
- Institute of Problems of Chemical Physics
- Chernogolovka
- Russia
| | - Boris Tsukerblat
- Department of Chemistry
- Ben-Gurion University of the Negev
- Beer-Sheva 84105
- Israel
| | | | | | - Eugenio Coronado
- Instituto de Ciencia Molecular
- Universidad de Valencia
- 46980 Paterna
- Spain
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10
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Götz KJG, Blien S, Stiller PL, Vavra O, Mayer T, Huber T, Meier TNG, Kronseder M, Strunk C, Hüttel AK. Co-sputtered MoRe thin films for carbon nanotube growth-compatible superconducting coplanar resonators. NANOTECHNOLOGY 2016; 27:135202. [PMID: 26901846 DOI: 10.1088/0957-4484/27/13/135202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Molybdenum rhenium alloy thin films can exhibit superconductivity up to critical temperatures of T(c)=15K. At the same time, the films are highly stable in the high-temperature methane/hydrogen atmosphere typically required to grow single wall carbon nanotubes. We characterize molybdenum rhenium alloy films deposited via simultaneous sputtering from two sources, with respect to their composition as function of sputter parameters and their electronic dc as well as GHz properties at low temperature. Specific emphasis is placed on the effect of the carbon nanotube growth conditions on the film. Superconducting coplanar waveguide resonators are defined lithographically; we demonstrate that the resonators remain functional when undergoing nanotube growth conditions, and characterize their properties as function of temperature. This paves the way for ultra-clean nanotube devices grown in situ onto superconducting coplanar waveguide circuit elements.
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Affiliation(s)
- K J G Götz
- Institute for Experimental and Applied Physics, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany
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11
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Rossella F, Bertoni A, Ercolani D, Rontani M, Sorba L, Beltram F, Roddaro S. Nanoscale spin rectifiers controlled by the Stark effect. NATURE NANOTECHNOLOGY 2014; 9:997-1001. [PMID: 25383514 DOI: 10.1038/nnano.2014.251] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 10/01/2014] [Indexed: 05/27/2023]
Abstract
The control of orbitals and spin states of single electrons is a key ingredient for quantum information processing and novel detection schemes and is, more generally, of great relevance for spintronics. Coulomb and spin blockade in double quantum dots enable advanced single-spin operations that would be available even for room-temperature applications with sufficiently small devices. To date, however, spin operations in double quantum dots have typically been observed at sub-kelvin temperatures, a key reason being that it is very challenging to scale a double quantum dot system while retaining independent field-effect control of individual dots. Here, we show that the quantum-confined Stark effect allows two dots only 5 nm apart to be independently addressed without the requirement for aligned nanometre-sized local gating. We thus demonstrate a scalable method to fully control a double quantum dot device, regardless of its physical size. In the present implementation we present InAs/InP nanowire double quantum dots that display an experimentally detectable spin blockade up to 10 K. We also report and discuss an unexpected re-entrant spin blockade lifting as a function of the magnetic field intensity.
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Affiliation(s)
- Francesco Rossella
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, I-56124 Pisa, Italy
| | - Andrea Bertoni
- S3, Istituto Nanoscienze-CNR, Via Campi 213a, I-41125 Modena, Italy
| | - Daniele Ercolani
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, I-56124 Pisa, Italy
| | - Massimo Rontani
- S3, Istituto Nanoscienze-CNR, Via Campi 213a, I-41125 Modena, Italy
| | - Lucia Sorba
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, I-56124 Pisa, Italy
| | - Fabio Beltram
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, I-56124 Pisa, Italy
| | - Stefano Roddaro
- NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, I-56124 Pisa, Italy
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12
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Buchs G, Bagiante S, Steele GA. Identifying signatures of photothermal current in a double-gated semiconducting nanotube. Nat Commun 2014; 5:4987. [DOI: 10.1038/ncomms5987] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Accepted: 08/15/2014] [Indexed: 11/09/2022] Open
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13
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Kim BK, Seo M, Cho SU, Chung Y, Kim N, Bae MH, Kim JJ. Tunable double and triple quantum dots in carbon nanotube with local side gates. NANOTECHNOLOGY 2014; 25:295201. [PMID: 24981295 DOI: 10.1088/0957-4484/25/29/295201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate a simple but efficient design for forming tunable single, double and triple quantum dots (QDs) in a sub-μm-long carbon nanotube (CNT) with two major features that distinguish this design from that of traditional CNT QDs: the use of i) Al2Ox tunnelling barriers between the CNT and metal contacts and ii) local side gates for controlling both the height of the potential barrier and the electron-confining potential profile to define multiple QDs. In a serial triple QD, in particular, we find that a stable molecular coupling state exists between two distant outer QDs. This state manifests in anti-crossing charging lines that correspond to electron and hole triple points for the outer QDs. The observed results are also reproduced in calculations based on a capacitive interaction model with reasonable configurations of electrons in the QDs. Our design using artificial tunnel contacts and local side gates provides a simple means of creating multiple QDs in CNTs for future quantum-engineering applications.
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Affiliation(s)
- Bum-Kyu Kim
- Department of Physics, Chonbuk National University, Jeonju 561-756, Republic of Korea. Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea
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14
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Sydoruk VA, Goß K, Meyer C, Petrychuk MV, Danilchenko BA, Weber P, Stampfer C, Li J, Vitusevich SA. Low-frequency noise in individual carbon nanotube field-effect transistors with top, side and back gate configurations: effect of gamma irradiation. NANOTECHNOLOGY 2014; 25:035703. [PMID: 24345726 DOI: 10.1088/0957-4484/25/3/035703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report on the influence of low gamma irradiation (10(4) Gy) on the noise properties of individual carbon nanotube (CNT) field-effect transistors (FETs) with different gate configurations and two different dielectric layers, SiO2 and Al2O3. Before treatment, strong generation-recombination (GR) noise components are observed. These data are used to identify several charge traps related to dielectric layers of the FETs by determining their activation energy. Investigation of samples with a single SiO2 dielectric layer as well as with two dielectric layers allows us to separate traps for each of the two dielectric layers. We reveal that each charge trap level observed in the side gate operation splits into two levels in top gate operation due to a different potential profile along the CNT channel. After gamma irradiation, only reduced flicker noise is registered in the noise spectra, which indicates a decrease of the number of charge traps. The mobility, which is estimated to be larger than 2 × 10(4) cm(2) V(-1) s(-1) at room temperature, decreases only slightly after radiation treatment, demonstrating high radiation hardness of the CNTs. Finally, we study the influence of Schottky barriers at the metal-nanotube interface on the transport properties of FETs, analyzing the behavior of the flicker noise component.
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Affiliation(s)
- V A Sydoruk
- Peter Grünberg Institute (PGI-6/8/9; IBG-2) and Jülich-Aachen Research Alliance for Future Information Technology (JARA-FIT), Forschungszentrum Jülich, D-52425 Jülich, Germany
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15
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Ji J, Zhou Z, Yang X, Zhang W, Sang S, Li P. One-dimensional nano-interconnection formation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:3014-3029. [PMID: 23606447 DOI: 10.1002/smll.201201318] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 11/01/2012] [Indexed: 06/02/2023]
Abstract
Interconnection of one-dimensional nanomaterials such as nanowires and carbon nanotubes with other parts or components is crucial for nanodevices to realize electrical contacts and mechanical fixings. Interconnection has been being gradually paid great attention since it is as significant as nanomaterials properties, and determines nanodevices performance in some cases. This paper provides an overview of recent progress on techniques that are commonly used for one-dimensional interconnection formation. In this review, these techniques could be categorized into two different types: two-step and one-step methods according to their established process. The two-step method is constituted by assembly and pinning processes, while the one-step method is a direct formation process of nano-interconnections. In both methods, the electrodeposition approach is illustrated in detail, and its potential mechanism is emphasized.
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Affiliation(s)
- Jianlong Ji
- MicroNano System Research Center, College of Information Engineering, Taiyuan University of Technology, Taiyuan, 030024, PR China
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Jung M, Schindele J, Nau S, Weiss M, Baumgartner A, Schönenberger C. Ultraclean single, double, and triple carbon nanotube quantum dots with recessed Re bottom gates. NANO LETTERS 2013; 13:4522-4526. [PMID: 23962122 DOI: 10.1021/nl402455n] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate that ultraclean single, double, and triple quantum dots (QDs) can be formed reliably in a carbon nanotube (CNT) by a straightforward fabrication technique. The QDs are electrostatically defined in the CNT by closely spaced metallic bottom gates deposited in trenches in SiO2 by sputter deposition of Re. The carbon nanotubes are then grown by chemical vapor deposition (CVD) across the trenches and contacted using conventional resist-based electron beam lithography. Unlike in previous work, the devices exhibit reproducibly the characteristics of ultraclean QDs behavior even after the subsequent electron beam lithography and chemical processing steps. We specifically demonstrate the high quality using CNT devices with two narrow bottom gates and one global back gate. Tunable by the gate voltages, the device can be operated in four different regimes: (i) fully p-type with ballistic transport between the outermost contacts (over a length of 700 nm), (ii) clean n-type single QD behavior where a QD can be induced by either the left or the right bottom gate, (iii) n-type double QD, and (iv) triple bipolar QD where the middle QD has opposite doping (p-type). Our simple fabrication scheme opens up a route to more complex devices based on ultraclean CNTs, since it allows for postgrowth processing.
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Affiliation(s)
- Minkyung Jung
- Department of Physics, University of Basel , Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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Waissman J, Honig M, Pecker S, Benyamini A, Hamo A, Ilani S. Realization of pristine and locally tunable one-dimensional electron systems in carbon nanotubes. NATURE NANOTECHNOLOGY 2013; 8:569-574. [PMID: 23912108 DOI: 10.1038/nnano.2013.143] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 06/19/2013] [Indexed: 06/02/2023]
Abstract
The ability to tune local parameters of quantum Hamiltonians has been demonstrated in experimental systems including ultracold atoms, trapped ions, superconducting circuits and photonic crystals. Such systems possess negligible disorder, enabling local tunability. Conversely, in condensed-matter systems, electrons are subject to disorder, which often destroys delicate correlated phases and precludes local tunability. The realization of a disorder-free and locally-tunable condensed-matter system thus remains an outstanding challenge. Here, we demonstrate a new technique for deterministic creation of locally-tunable, ultralow-disorder electron systems in carbon nanotubes suspended over complex electronic circuits. Using transport experiments we show that electrons can be localized at any position along the nanotube and that the confinement potential can be smoothly moved from location to location. The high mirror symmetry of transport characteristics about the nanotube centre establishes the negligible effects of electronic disorder, thus allowing experiments in precision-engineered one-dimensional potentials. We further demonstrate the ability to position multiple nanotubes at chosen separations, generalizing these devices to coupled one-dimensional systems. These capabilities could enable many novel experiments on electronics, mechanics and spins in one dimension.
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Affiliation(s)
- J Waissman
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
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18
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Laird EA, Pei F, Kouwenhoven LP. A valley-spin qubit in a carbon nanotube. NATURE NANOTECHNOLOGY 2013; 8:565-568. [PMID: 23892984 DOI: 10.1038/nnano.2013.140] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 06/18/2013] [Indexed: 06/02/2023]
Abstract
Although electron spins in III-V semiconductor quantum dots have shown great promise as qubits, hyperfine decoherence remains a major challenge in these materials. Group IV semiconductors possess dominant nuclear species that are spinless, allowing qubit coherence times up to 2 s. In carbon nanotubes, where the spin-orbit interaction allows for all-electrical qubit manipulation, theoretical predictions of the coherence time vary by at least six orders of magnitude and range up to 10 s or more. Here, we realize a qubit encoded in two nanotube valley-spin states, with coherent manipulation via electrically driven spin resonance mediated by a bend in the nanotube. Readout uses Pauli blockade leakage current through a double quantum dot. Arbitrary qubit rotations are demonstrated and the coherence time is measured for the first time via Hahn echo, allowing comparison with theoretical predictions. The coherence time is found to be ∼65 ns, probably limited by electrical noise. This shows that, even with low nuclear spin abundance, coherence can be strongly degraded if the qubit states are coupled to electric fields.
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Affiliation(s)
- E A Laird
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands
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19
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Ribeiro H, Burkard G. Join the dots. NATURE MATERIALS 2013; 12:467. [PMID: 23695730 DOI: 10.1038/nmat3681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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20
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Large spin-orbit coupling in carbon nanotubes. Nat Commun 2013; 4:1573. [DOI: 10.1038/ncomms2584] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 02/08/2013] [Indexed: 11/09/2022] Open
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Pribiag VS, Nadj-Perge S, Frolov SM, van den Berg JWG, van Weperen I, Plissard SR, Bakkers EPAM, Kouwenhoven LP. Electrical control of single hole spins in nanowire quantum dots. NATURE NANOTECHNOLOGY 2013; 8:170-174. [PMID: 23416794 DOI: 10.1038/nnano.2013.5] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 01/09/2013] [Indexed: 06/01/2023]
Abstract
The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes.
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Affiliation(s)
- V S Pribiag
- Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands.
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Sharf T, Kevek JW, Deborde T, Wardini JL, Minot ED. Origins of charge noise in carbon nanotube field-effect transistor biosensors. NANO LETTERS 2012; 12:6380-6384. [PMID: 23171196 DOI: 10.1021/nl303651t] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Determining the major noise sources in nanoscale field-effect transistor (nanoFET) biosensors is critical for improving bioelectronic interfaces. We use the carbon nanotube (CNT) FET biosensor platform to examine the noise generated by substrate interactions and surface adsorbates, both of which are present in current nanoFET biosensors. The charge noise model is used as a quantitative framework to show that insulating substrates and surface adsorbates are both significant contributors to the noise floor of CNT FET biosensors. Removing substrate interactions and surface adsorbates reduces the power spectral density of background voltage fluctuations by 19-fold.
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Affiliation(s)
- Tal Sharf
- Department of Physics, Oregon State University, Corvallis, Oregon 97331-6507, United States
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Barkelid M, Steele GA, Zwiller V. Probing optical transitions in individual carbon nanotubes using polarized photocurrent spectroscopy. NANO LETTERS 2012; 12:5649-5653. [PMID: 23066947 DOI: 10.1021/nl302789k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Carbon nanotubes show vast potential to be used as building blocks for photodetection applications. However, measurements of fundamental optical properties, such as the absorption coefficient and the dielectric constant, have not been accurately performed on a single pristine carbon nanotube. Here we show polarization-dependent photocurrent spectroscopy, performed on a p-n junction in a single suspended semiconducting carbon nanotube. We observe an enhanced absorption in the carbon nanotube optical resonances, and an external quantum efficiency of 12.3% and 8.7% was deduced for the E11 and E22 transitions, respectively. By studying the polarization dependence of the photocurrent, a dielectric constant of 3.6 ± 0.2 was experimentally determined for this semiconducting carbon nanotube.
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Affiliation(s)
- Maria Barkelid
- Quantum Transport Group, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
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Pei F, Laird EA, Steele GA, Kouwenhoven LP. Valley-spin blockade and spin resonance in carbon nanotubes. NATURE NANOTECHNOLOGY 2012; 7:630-634. [PMID: 23001302 DOI: 10.1038/nnano.2012.160] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Accepted: 08/16/2012] [Indexed: 06/01/2023]
Abstract
The manipulation and readout of spin qubits in quantum dots have been successfully achieved using Pauli blockade, which forbids transitions between spin-triplet and spin-singlet states. Compared with spin qubits realized in III-V materials, group IV materials such as silicon and carbon are attractive for this application because of their low decoherence rates (nuclei with zero spins). However, valley degeneracies in the electronic band structure of these materials combined with Coulomb interactions reduce the energy difference between the blocked and unblocked states, significantly weakening the selection rules for Pauli blockade. Recent demonstrations of spin qubits in silicon devices have required strain and spatial confinement to lift the valley degeneracy. In carbon nanotubes, Pauli blockade can be observed by lifting valley degeneracy through disorder, but this makes the confinement potential difficult to control. To achieve Pauli blockade in low-disorder nanotubes, quantum dots have to be made ultrasmall, which is incompatible with conventional fabrication methods. Here, we exploit the bandgap of low-disorder nanotubes to demonstrate robust Pauli blockade based on both valley and spin selection rules. We use a novel stamping technique to create a bent nanotube, in which single-electron spin resonance is detected using the blockade. Our results indicate the feasibility of valley-spin qubits in carbon nanotubes.
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Affiliation(s)
- Fei Pei
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA, Delft, The Netherlands
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25
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Coupling carbon nanotube mechanics to a superconducting circuit. Sci Rep 2012; 2:599. [PMID: 22953042 PMCID: PMC3432457 DOI: 10.1038/srep00599] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 08/09/2012] [Indexed: 11/08/2022] Open
Abstract
The quantum behaviour of mechanical resonators is a new and emerging field driven by recent experiments reaching the quantum ground state. The high frequency, small mass, and large quality-factor of carbon nanotube resonators make them attractive for quantum nanomechanical applications. A common element in experiments achieving the resonator ground state is a second quantum system, such as coherent photons or a superconducting device, coupled to the resonators motion. For nanotubes, however, this is a challenge due to their small size. Here, we couple a carbon nanoelectromechanical (NEMS) device to a superconducting circuit. Suspended carbon nanotubes act as both superconducting junctions and moving elements in a Superconducting Quantum Interference Device (SQUID). We observe a strong modulation of the flux through the SQUID from displacements of the nanotube. Incorporating this SQUID into superconducting resonators and qubits should enable the detection and manipulation of nanotube mechanical quantum states at the single-phonon level.
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26
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Prati E, Hori M, Guagliardo F, Ferrari G, Shinada T. Anderson-Mott transition in arrays of a few dopant atoms in a silicon transistor. NATURE NANOTECHNOLOGY 2012; 7:443-447. [PMID: 22751223 DOI: 10.1038/nnano.2012.94] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 05/10/2012] [Indexed: 06/01/2023]
Abstract
Dopant atoms are used to control the properties of semiconductors in most electronic devices. Recent advances such as single-ion implantation have allowed the precise positioning of single dopants in semiconductors as well as the fabrication of single-atom transistors, representing steps forward in the realization of quantum circuits. However, the interactions between dopant atoms have only been studied in systems containing large numbers of dopants, so it has not been possible to explore fundamental phenomena such as the Anderson-Mott transition between conduction by sequential tunnelling through isolated dopant atoms, and conduction through thermally activated impurity Hubbard bands. Here, we observe the Anderson-Mott transition at low temperatures in silicon transistors containing arrays of two, four or six arsenic dopant atoms that have been deterministically implanted along the channel of the device. The transition is induced by controlling the spacing between dopant atoms. Furthermore, at the critical density between tunnelling and band transport regimes, we are able to change the phase of the electron system from a frozen Wigner-like phase to a Fermi glass by increasing the temperature. Our results open up new approaches for the investigation of coherent transport, band engineering and strongly correlated systems in condensed-matter physics.
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Affiliation(s)
- Enrico Prati
- Laboratorio MDM, IMM-CNR, Via Olivetti 2, Agrate Brianza, Italy.
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Ganzhorn M, Wernsdorfer W. Dynamics and dissipation induced by single-electron tunneling in carbon nanotube nanoelectromechanical systems. PHYSICAL REVIEW LETTERS 2012; 108:175502. [PMID: 22680883 DOI: 10.1103/physrevlett.108.175502] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2011] [Revised: 01/28/2012] [Indexed: 05/05/2023]
Abstract
We demonstrate the effect of single-electron tunneling (SET) through a carbon nanotube quantum dot on its nanomechanical motion. We find that the frequency response and the dissipation of the nanoelectromechanical system to SET strongly depends on the electronic environment of the quantum dot, in particular, on the total dot capacitance and the tunnel coupling to the metal contacts. Our findings suggest that one could achieve quality factors of 10(6) or higher by choosing appropriate gate dielectrics and/or by improving the tunnel coupling to the leads.
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Affiliation(s)
- Marc Ganzhorn
- Institut Néel, CNRS & Université Joseph Fourier, Grenoble, France
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29
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Snyman I, Nazarov YV. Polarons in suspended carbon nanotubes. PHYSICAL REVIEW LETTERS 2012; 108:076805. [PMID: 22401239 DOI: 10.1103/physrevlett.108.076805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Indexed: 05/31/2023]
Abstract
We prove theoretically the possibility of electric-field controlled polaron formation involving flexural (bending) modes in suspended carbon nanotubes. Upon increasing the field, the ground state of the system with a single extra electron undergoes a first-order phase transition between an extended state and a localized polaron state. For a common experimental setup, the threshold electric field is only of the order of approximately equal 5×10(-2) V/μm.
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Affiliation(s)
- I Snyman
- National Institute for Theoretical Physics, Matieland, South Africa.
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30
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Laird EA, Pei F, Tang W, Steele GA, Kouwenhoven LP. A high quality factor carbon nanotube mechanical resonator at 39 GHz. NANO LETTERS 2012; 12:193-197. [PMID: 22111547 DOI: 10.1021/nl203279v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We measure the mechanical resonances of an as-grown suspended carbon nanotube, detected via electrical mixing in the device. A sequence of modes extending to 39 GHz is observed with a quality factor of 35,000 in the highest mode. This unprecedentedly high combination corresponds to a thermal excited state probability below 10(-8) and a relaxation time of 140 ns with microsecond relaxation times for lower modes. The effect of electron tunneling on the mechanical resonance is found to depend on frequency as the tunneling time becomes comparable to the vibration period.
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Affiliation(s)
- Edward A Laird
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
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31
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Hu Y, Kuemmeth F, Lieber CM, Marcus CM. Hole spin relaxation in Ge-Si core-shell nanowire qubits. NATURE NANOTECHNOLOGY 2011; 7:47-50. [PMID: 22179569 DOI: 10.1038/nnano.2011.234] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 11/21/2011] [Indexed: 05/27/2023]
Abstract
Controlling decoherence is the biggest challenge in efforts to develop quantum information hardware. Single electron spins in gallium arsenide are a leading candidate among implementations of solid-state quantum bits, but their strong coupling to nuclear spins produces high decoherence rates. Group IV semiconductors, on the other hand, have relatively low nuclear spin densities, making them an attractive platform for spin quantum bits. However, device fabrication remains a challenge, particularly with respect to the control of materials and interfaces. Here, we demonstrate state preparation, pulsed gate control and charge-sensing spin readout of hole spins confined in a Ge-Si core-shell nanowire. With fast gating, we measure T(1) spin relaxation times of up to 0.6 ms in coupled quantum dots at zero magnetic field. Relaxation time increases as the magnetic field is reduced, which is consistent with a spin-orbit mechanism that is usually masked by hyperfine contributions.
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Affiliation(s)
- Yongjie Hu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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32
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Salger T, Grossert C, Kling S, Weitz M. Klein tunneling of a quasirelativistic Bose-Einstein condensate in an optical lattice. PHYSICAL REVIEW LETTERS 2011; 107:240401. [PMID: 22242978 DOI: 10.1103/physrevlett.107.240401] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Indexed: 05/31/2023]
Abstract
A proof-of-principle experiment simulating effects predicted by relativistic wave equations with ultracold atoms in a bichromatic optical lattice that allows for a tailoring of the dispersion relation is reported. We observe the analog of Klein tunneling, the penetration of relativistic particles through a potential barrier without the exponential damping that is characteristic for nonrelativistic quantum tunneling. Both linear (relativistic) and quadratic (nonrelativistic) dispersion relations are investigated, and significant barrier transmission is observed only for the relativistic case.
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Affiliation(s)
- Tobias Salger
- Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.
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Nam SG, Ki DK, Park JW, Kim Y, Kim JS, Lee HJ. Ballistic transport of graphene pnp junctions with embedded local gates. NANOTECHNOLOGY 2011; 22:415203. [PMID: 21914932 DOI: 10.1088/0957-4484/22/41/415203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We fabricated graphene pnp devices, by embedding pre-defined local gates in an oxidized surface layer of a silicon substrate. With neither deposition of dielectric material on the graphene nor electron-beam irradiation, we obtained high-quality graphene pnp devices without degradation of the carrier mobility even in the local-gate region. The corresponding increased mean free path leads to the observation of ballistic and phase-coherent transport across a local gate 130 nm wide, which is about an order of magnitude wider than reported previously. Furthermore, in our scheme, we demonstrated independent control of the carrier density in the local-gate region, with a conductance map very much distinct from those of top-gated devices. This was caused by the electric field arising from the global back gate being strongly screened by the embedded local gate. Our scheme allows the realization of ideal multipolar graphene junctions with ballistic carrier transport.
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Affiliation(s)
- Seung-Geol Nam
- Department of Physics, Pohang University of Science and Technology, Pohang, Republic of Korea
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34
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Eichler A, Chaste J, Moser J, Bachtold A. Parametric amplification and self-oscillation in a nanotube mechanical resonator. NANO LETTERS 2011; 11:2699-2703. [PMID: 21615135 DOI: 10.1021/nl200950d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A hallmark of mechanical resonators made from a single nanotube is that the resonance frequency can be widely tuned. Here, we take advantage of this property to realize parametric amplification and self-oscillation. The gain of the parametric amplification can be as high as 18.2 dB and tends to saturate at high parametric pumping due to nonlinear damping. These measurements allow us to determine the coefficient of the linear damping force. The corresponding damping rate is lower than the one obtained from the line shape of the resonance (without pumping), supporting the recently reported scenario that describes damping in nanotube resonators by a nonlinear force. The possibility to combine nanotube resonant mechanics and parametric amplification holds promise for future ultralow force sensing experiments.
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Affiliation(s)
- Alexander Eichler
- Catalan Institute of Nanotechnology (ICN) and CIN2, Campus UAB, 08193 Bellaterra, Barcelona, Spain
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35
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Klinovaja J, Schmidt MJ, Braunecker B, Loss D. Helical modes in carbon nanotubes generated by strong electric fields. PHYSICAL REVIEW LETTERS 2011; 106:156809. [PMID: 21568600 DOI: 10.1103/physrevlett.106.156809] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Indexed: 05/30/2023]
Abstract
Helical modes, conducting opposite spins in opposite directions, are shown to exist in metallic armchair nanotubes in an all-electric setup. This is a consequence of the interplay between spin-orbit interaction and strong electric fields. The helical regime can also be obtained in chiral metallic nanotubes by applying an additional magnetic field. In particular, it is possible to obtain helical modes at one of the two Dirac points only, while the other one remains gapped. Starting from a tight-binding model we derive the effective low-energy Hamiltonian and the resulting spectrum.
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Affiliation(s)
- Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
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36
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Pályi A, Burkard G. Disorder-mediated electron valley resonance in carbon nanotube quantum dots. PHYSICAL REVIEW LETTERS 2011; 106:086801. [PMID: 21405589 DOI: 10.1103/physrevlett.106.086801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Indexed: 05/30/2023]
Abstract
We propose a scheme for coherent rotation of the valley isospin of a single electron confined in a carbon nanotube quantum dot. The scheme exploits the ubiquitous atomic disorder of the nanotube crystal lattice, which induces time-dependent valley mixing as the confined electron is pushed back and forth along the nanotube axis by an applied ac electric field. Using experimentally determined values for the disorder strength we estimate that valley Rabi oscillations with a period on the nanosecond time scale are feasible. The valley resonance effect can be detected in the electric current through a double quantum dot in the single-electron transport regime.
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Affiliation(s)
- András Pályi
- Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
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37
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Sharma M, Ghosh S. Electron transport and Goos-Hänchen shift in graphene with electric and magnetic barriers: optical analogy and band structure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:055501. [PMID: 21406909 DOI: 10.1088/0953-8984/23/5/055501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Transport of massless Dirac fermions in graphene monolayers is analysed in the presence of a combination of singular magnetic barriers and applied electrostatic potential. Extending a recently proposed (Ghosh and Sharma 2009 J. Phys.: Condens. Matter 21 292204) analogy between the transmission of light through a medium with modulated refractive index and electron transmission in graphene through singular magnetic barriers to the present case, we find the addition of a scalar potential profoundly changes the transmission. We calculate the quantum version of the Goos-Hänchen shift that the electron wave suffers upon being totally reflected by such barriers. The combined electric and magnetic barriers substantially modify the band structure near the Dirac point. This affects transport near the Dirac point significantly and has important consequences for graphene-based electronics.
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Affiliation(s)
- Manish Sharma
- Centre for Applied Research in Electronics, Indian Institute of Technology Delhi, New Delhi-110016, India
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Muoth M, Helbling T, Durrer L, Lee SW, Roman C, Hierold C. Hysteresis-free operation of suspended carbon nanotube transistors. NATURE NANOTECHNOLOGY 2010; 5:589-92. [PMID: 20601944 DOI: 10.1038/nnano.2010.129] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 05/21/2010] [Indexed: 05/08/2023]
Abstract
Single-walled carbon nanotubes offer high sensitivity and very low power consumption when used as field-effect transistors in nanosensors. Suspending nanotubes between pairs of contacts, rather than attaching them to a surface, has many advantages in chemical, optical or displacement sensing applications, as well as for resonant electromechanical systems. Suspended nanotubes can be integrated into devices after nanotube growth, but contamination caused by the accompanying additional process steps can change device properties. Ultraclean suspended nanotubes can also be grown between existing device contacts, but high growth temperatures limit the choice of metals that can be used as contacts. Moreover, when operated in ambient conditions, devices fabricated by either the post- or pre-growth approach typically exhibit gate hysteresis, which makes device behaviour less reproducible. Here, we report the operation of nanotube transistors in a humid atmosphere without hysteresis. Suspended, individual and ultraclean nanotubes are grown directly between unmetallized device contacts, onto which palladium is then evaporated through self-aligned on-chip shadow masks. This yields pairs of needle-shaped source/drain contacts that have been theoretically shown to allow high nanotube-gate coupling and low gate voltages. This process paves the way for creating ultrasensitive nanosensors based on pristine suspended nanotubes.
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Affiliation(s)
- M Muoth
- Micro and Nanosystems, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland.
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Abstract
This is a review on graphene quantum dots and their use as a host for spin qubits. We discuss the advantages but also the challenges to use graphene quantum dots for spin qubits as compared to the more standard materials like GaAs. We start with an overview of this young and fascinating field and then discuss gate-tunable quantum dots in detail. We calculate the bound states for three different quantum dot architectures where a bulk gap allows for confinement via electrostatic fields: (i) graphene nanoribbons with armchair boundaries, (ii) a disc in single-layer graphene, and (iii) a disc in bilayer graphene. In order for graphene quantum dots to be useful in the context of spin qubits, one needs to find reliable ways to break the valley degeneracy. This is achieved here, either by a specific termination of graphene in (i) or in (ii) and (iii) by a magnetic field, without the need of a specific boundary. We further discuss how to manipulate spin in these quantum dots and explain the mechanism of spin decoherence and relaxation caused by spin-orbit interaction in combination with electron-phonon coupling, and by hyperfine interaction with the nuclear-spin system.
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Affiliation(s)
- Patrik Recher
- Institut für Theoretische Physik und Astrophysik, University of Würzburg, Würzburg, Germany.
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40
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Moura FV, de Oliveira Massa L, de Oliveira Neto PH, Gargano R, Qu F. Electronic structure of vertically coupled double quantum dots: Optimization of basis functions. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.05.092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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41
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Rinkiö M, Johansson A, Kotimäki V, Törmä P. Negative differential resistance in carbon nanotube field-effect transistors with patterned gate oxide. ACS NANO 2010; 4:3356-62. [PMID: 20524681 DOI: 10.1021/nn100208v] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We demonstrate controllable and gate-tunable negative differential resistance in carbon nanotube field-effect transistors, at room temperature and at 4.2 K. This is achieved by effectively creating quantum dots along the carbon nanotube channel by patterning the underlying, high-kappa gate oxide. The negative differential resistance feature can be modulated by both the gate and the drain-source voltage, which leads to more than 20% change of the current peak-to-valley ratio. Our approach is fully scalable and opens up a possibility for a new class of nanoscale electronic devices using negative differential resistance in their operation.
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Affiliation(s)
- Marcus Rinkiö
- Department of Physics, Nanoscience Center, P.O. Box 35, FI-40014 University of Jyvaskyla, Finland
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42
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Stokes P, Khondaker SI. Evaluating defects in solution-processed carbon nanotube devices via low-temperature transport spectroscopy. ACS NANO 2010; 4:2659-2666. [PMID: 20377242 DOI: 10.1021/nn100284j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We performed low-temperature electron transport spectroscopy to evaluate defects in individual single-walled carbon nanotube (SWNT) devices assembled via dielectrophoresis from a surfactant-free solution. At 4.2 K, the majority of the devices show periodic and well-defined Coulomb diamonds near zero gate voltage corresponding to transport through a single quantum dot, while at higher gate voltages, beating behavior is observed due to small potential fluctuations induced by the substrate. The Coulomb diamonds were further modeled using a single electron transistor simulator. Our study suggests that SWNTs derived from stable solutions in this work are free from hard defects and are relatively clean. Our observations have strong implications on the use of solution-processed SWNTs for future nanoelectronic device applications.
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Affiliation(s)
- Paul Stokes
- Department of Physics, University of Central Florida, Nanoscience Technology Center, Orlando, Florida 32826, USA
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43
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Liu XL, Hug D, Vandersypen LMK. Gate-defined graphene double quantum dot and excited state spectroscopy. NANO LETTERS 2010; 10:1623-1627. [PMID: 20377196 DOI: 10.1021/nl9040912] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A double quantum dot is formed in a graphene nanoribbon device using three top gates. These gates independently change the number of electrons on each dot and tune the interdot coupling. Transport through excited states is observed in the weakly coupled double dot regime. We extract from the measurements all relevant capacitances of the double dot system, as well as the quantized level spacing.
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Affiliation(s)
- Xing Lan Liu
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
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44
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Wang Z, Wei J, Morse P, Dash JG, Vilches OE, Cobden DH. Phase Transitions of Adsorbed Atoms on the Surface of a Carbon Nanotube. Science 2010; 327:552-5. [DOI: 10.1126/science.1182507] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Zenghui Wang
- Department of Physics, University of Washington, Seattle, WA 98195–1560, USA
| | - Jiang Wei
- Department of Physics, University of Washington, Seattle, WA 98195–1560, USA
| | - Peter Morse
- Department of Physics, University of Washington, Seattle, WA 98195–1560, USA
| | - J. Gregory Dash
- Department of Physics, University of Washington, Seattle, WA 98195–1560, USA
| | - Oscar E. Vilches
- Department of Physics, University of Washington, Seattle, WA 98195–1560, USA
| | - David H. Cobden
- Department of Physics, University of Washington, Seattle, WA 98195–1560, USA
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45
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Steele GA, Hüttel AK, Witkamp B, Poot M, Meerwaldt HB, Kouwenhoven LP, van der Zant HSJ. Strong Coupling Between Single-Electron Tunneling and Nanomechanical Motion. Science 2009; 325:1103-7. [DOI: 10.1126/science.1176076] [Citation(s) in RCA: 322] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- G. A. Steele
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
| | - A. K. Hüttel
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
| | - B. Witkamp
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
| | - M. Poot
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
| | - H. B. Meerwaldt
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
| | - L. P. Kouwenhoven
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
| | - H. S. J. van der Zant
- Kavli Institute of NanoScience, Delft University of Technology, Post Office Box 5046, 2600 GA, Delft, Netherlands
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46
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Hüttel AK, Steele GA, Witkamp B, Poot M, Kouwenhoven LP, van der Zant HSJ. Carbon nanotubes as ultrahigh quality factor mechanical resonators. NANO LETTERS 2009; 9:2547-52. [PMID: 19492820 DOI: 10.1021/nl900612h] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have observed the transversal vibration mode of suspended carbon nanotubes at millikelvin temperatures by measuring the single-electron tunneling current. The suspended nanotubes are actuated contact-free by the radio frequency electric field of a nearby antenna; the mechanical resonance is detected in the time-averaged current through the nanotube. Sharp, gate-tunable resonances due to the bending mode of the nanotube are observed, combining resonance frequencies of up to nu(0) = 350 MHz with quality factors above Q = 10(5), much higher than previously reported results on suspended carbon nanotube resonators. The measured magnitude and temperature dependence of the Q factor shows a remarkable agreement with the intrinsic damping predicted for a suspended carbon nanotube. By adjusting the radio frequency power on the antenna, we find that the nanotube resonator can easily be driven into the nonlinear regime.
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Affiliation(s)
- Andreas K Hüttel
- Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands
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47
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Choi MS. Quantum dots: When a barrier is not an obstacle. NATURE NANOTECHNOLOGY 2009; 4:347-348. [PMID: 19498393 DOI: 10.1038/nnano.2009.134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Affiliation(s)
- Mahn-Soo Choi
- Department of Physics, Korea University, Seoul 136-713, Korea.
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