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Low-temperature quantum transport in CVD-grown single crystal graphene

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Nano Research 2016年第6期9卷 1823-1830页

作者： Shaohua Xiang Vaidotas Miseikis Luca Planat Stefano Guiducci Stefano Roddaro Camilla Coletti fabio beltram Stefan Heun NEST Istituto Nanoscienze--CNR and Scuola Normale Superiore Piazza San Silvestro 12 $6127 Pisa Italy Center for Nanotechnology Innovation @NEST Istituto Italiano di Tecnologia Piazza San Silvestro 12 56127 Pisa Italy

Chemical vapor deposition （CVD） is typically used for large-scale graphene synthesis for practical applications. However, the inferior electronic properties of CVD graphene are one of the key problems to be solved. Therefore, we present a detailed study on the electronic properties of high-quality single-crystal monolayer graphene. The graphene is grown via CVD on copper, by using a cold-wall reactor, and then transferred to Si/SiO2. Our low-temperature magneto-transport data demonstrate that the characteristics of the single-crystal CVD graphene samples are superior to those of polycrystalline graphene and have a quality which is comparable to that of exfoliated graphene on Si/SiO2. The Dirac point in our best samples occurs at back-gate voltages lower than 10 V, and a maximum mobility of 11,000 cm2/（V.s） is attained. More than 12 flat and discernible half-integer quantum Hall plateaus occur under a high magnetic field on both the electron and hole sides of the Dirac point. At a low magnetic field, the magnetoresistance exhibits a weak localization peak. Using the theory of McCann et al., we obtain inelastic scattering lengths of 〉1 um, even at the charge neutrality point of the samples.

关键词： high-quality chemicalvapor deposition （CVD）-graphene,low-temperaturemagnetotransport,quantum Hall effect,weak localization

Large thermal biasing of individual gated nanostructures

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Nano Research 2014年第4期7卷 579-587页

作者： Stefano Roddaro Daniele Ercolani Mian Akif Safeen Francesco Rossella Vincenzo Piazza Francesco Giazotto Lucia Sorba fabio beltram NEST Scuola Normale Superiore and Istituto Nanoscienze-CNR Piazza S. Silvestro 121-56127 Pisa Italy Istituto Officina dei Materiali - CNR Basovizza S.S. 14 km 163.51-34149 Trieste Italy Center for Nanotechnology Innovation @NEST Istituto Italiano di Tecnologia Piazza San Silvestro 12 56127 Pisa Italy

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.

关键词：纳米结构偏压门控温度梯度电阻加热器场效应氧化层纳米线

Electrical probing of carrier separation in InAs/InP/GaAsSb core-dualshell nanowires

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Nano Research 2020年第4期13卷 1065-1070页

作者： Sedighe Salimian Omer Arif Valentina Zannier Daniele Ercolani Francesca Rossi Zahra Sadre Momtaz fabio beltram Sefano Roddaro Francesco Rossella Lucia Sorba NEST Istituto Nanoscienze-CNR and Scuola Normale SuperiorePiazza S.Silvestro 121-56127 PisaItaly IMEM-CNR Institute Parco Area delle Scienze 37/A43124 ParmaItaly Department of Physics"E.Fermi" Universita di PisaLargo Pontecorvo 31-56127 PisaItaly

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.***.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.

关键词： core-dualshell nanowires charge carrier separation semiconductor nanowires nanoelectronics

Atomic and electronic structure of Si dangling bonds in quasi-free-standing monolayer graphene

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Nano Research 2018年第2期11卷 864-873页

作者： Yuya Murata Tommaso Cavallucci Valentina Tozzini Niko Pavliček Leo Gross Gerhard Meyer Makoto Takamura Hiroki Hibino fabio beltram Stefan Heun NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore Pisa Italy IBM Research-Zurich Rüschlikon Switzerland NTT Basic Research Laboratories Atsugi Kanagawa Japan

Si dangling bonds at the interface of quasi-free-standing monolayer graphene （QFMLG） are known to act as scattering centers that can severely affect carrier mobility Herein, we investigate the atomic and electronic structure of Si dangling bonds in QFMLG using low-temperature scanning tunneling microscopy/ spectroscopy （STM/STS）, atomic force microscopy （AFM）, and density functional theory （DFT） calculations. Two types of defects with different contrast were observed on a flat graphene terrace by STM and AFM; in particular, their STM contrast varied with the bias voltage. Moreover, these defects showed characteristic STS peaks at different energies, 1.1 and 1.4 eV. The comparison of the experimental data with the DFT calculations indicates that the defects with STS peak energies of 1.1 and 1.4 eV consist of clusters of three and four Si dangling bonds, respectively. The relevance of the present results for the optimization of graphene synthesis is discussed.

关键词： quasi-free-standingmonolayer graphene,hydrogen intercalation,carrier mobility,scanning tunnelingmicroscopy,scanning tunnelingspectroscop^atomic force microscop3~density functional theory

Scanning gate imaging of quantum point contacts and the origin of the 0.7 anomaly

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Nano Research 2015年第3期8卷 948-956页

作者： Andrea lagallo Nicola Paradiso Stefano Roddaro Christian Reichl Werner Wegscheider Giorgio Biasiol Lucia Sorba fabio beltram Stefan Heun National Enterprise for Nanoscience and Nanotechnology (NEST) Istituto Nanoscienze-CNR and Scuola Normale Superiore Piazza San Silvestro 12 56127 Pisa Italy Istituto Offcina dei Materiali CNR Laboratorio TASC 34149 Trieste Italy Solid State Physics Laboratory ETH Zurich Schafmattstrasse 16 8093 Zurich Switzerland

出现在传导力 G 0.7 睯物 ? 的异常运输特征的起源 ???????????? 瀠潲慰慧楴湯景 ? 慮潮楷敲？？

关键词：扫描成像量子点接触异常起源大门电导特性反常输运量子干涉

Anisotropies of the g-factor tensor and diamagnetic coefficient in crystal-phase quantum dots in InP nanowires

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Nano Research 2019年第11期12卷 2842-2848页

作者： Shiyao Wu Kai Peng Sergio Battiato Valentina Zannier Andrea Bertoni Guido Goldoni Xin Xie Jingnan Yang Shan Xiao Chenjiang Qian Feilong Song Sibai Sun Jianchen Dang Yang Yu fabio beltram Lucia Sorba Ang Li Bei-bei Li Francesco Rossella Xiulai Xu Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing100190China CAS Center for Excellence in Topological Quantum Computation and School of Physical Sciences University of Chinese Academy of SciencesBeijing100049China Laboratorio NEST Scuola Normale Superiore and Istituto Nanoscienze-CNRPiazza S.Silvestro 12I-56127PisaItaly S3 Istituto Nanoscienze-CNRVia Campi 213/aModena41125Italy Dipartimento di Scienze Fisiche Informatiche e MatematicheUniversitàdegli Studi di Modena e Reggio EmiliaVia Campi 213/aModena41125Italy Beijing Key Lab of Microstructure and Property of Advanced Materials Beijing University of TechnologyPingleyuan No.100Beijing100024China Songshan Lake Materials Laboratory Dongguan523808China

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.

关键词： g-factor tensor diamagnetic coefficient crystal-phase quantum dot InP NWs