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Hnatovsky C, Mihailov S, Hilke M, Pfeiffer L, West K, Studenikin S. An Optical Technique to Produce Embedded Quantum Structures in Semiconductors. Nanomaterials (Basel) 2023; 13:nano13101622. [PMID: 37242039 DOI: 10.3390/nano13101622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 04/30/2023] [Accepted: 05/10/2023] [Indexed: 05/28/2023]
Abstract
The performance of a semiconductor quantum-electronic device ultimately depends on the quality of the semiconductor materials it is made of and on how well the device is isolated from electrostatic fluctuations caused by unavoidable surface charges and other sources of electric noise. Current technology to fabricate quantum semiconductor devices relies on surface gates which impose strong limitations on the maximum distance from the surface where the confining electrostatic potentials can be engineered. Surface gates also introduce strain fields which cause imperfections in the semiconductor crystal structure. Another way to create confining electrostatic potentials inside semiconductors is by means of light and photosensitive dopants. Light can be structured in the form of perfectly parallel sheets of high and low intensity which can penetrate deep into a semiconductor and, importantly, light does not deteriorate the quality of the semiconductor crystal. In this work, we employ these important properties of structured light to form metastable states of photo-sensitive impurities inside a GaAs/AlGaAs quantum well structure in order to create persistent periodic electrostatic potentials at large predetermined distances from the sample surface. The amplitude of the light-induced potential is controlled by gradually increasing the light fluence at the sample surface and simultaneously measuring the amplitude of Weiss commensurability oscillations in the magnetoresistivity.
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Affiliation(s)
- Cyril Hnatovsky
- Emerging Technologies Division, National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
| | - Stephen Mihailov
- Emerging Technologies Division, National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
| | - Michael Hilke
- Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada
| | - Loren Pfeiffer
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Ken West
- Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Sergei Studenikin
- Emerging Technologies Division, National Research Council of Canada, Ottawa, ON K1A 0R6, Canada
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2
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Murtaza G, Colautti M, Hilke M, Lombardi P, Cataliotti FS, Zavatta A, Bacco D, Toninelli C. Efficient room-temperature molecular single-photon sources for quantum key distribution. Opt Express 2023; 31:9437-9447. [PMID: 37157515 DOI: 10.1364/oe.476440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Quantum key distribution (QKD) allows the distribution of cryptographic keys between multiple users in an information-theoretic secure way, exploiting quantum physics. While current QKD systems are mainly based on attenuated laser pulses, deterministic single-photon sources could give concrete advantages in terms of secret key rate (SKR) and security owing to the negligible probability of multi-photon events. Here, we introduce and demonstrate a proof-of-concept QKD system exploiting a molecule-based single-photon source operating at room temperature and emitting at 785 nm. With an estimated maximum SKR of 0.5 Mbps, our solution paves the way for room-temperature single-photon sources for quantum communication protocols.
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3
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Trettin M, Dvořák J, Hilke M, Wenzler S, Hagen M, Ghirmai N, Stäblein M, Matura S, Huthmacher AC, Kraft D, Balaban C, Ciaramidaro A, Prvulovic D, Knöchel C, Reif A, Oertel V. Neuronal response to high negative affective stimuli in major depressive disorder: An fMRI study. J Affect Disord 2022; 298:239-247. [PMID: 34728281 DOI: 10.1016/j.jad.2021.10.123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 09/28/2021] [Accepted: 10/20/2021] [Indexed: 10/19/2022]
Abstract
BACKGROUND Disturbed emotion processing underlies depression. We examined the neuronal underpinnings of emotional processing in patients (PAT) with major depressive disorder (MDD) compared to healthy volunteers (HV) using functional magnetic resonance (fMRI) scan. METHODS Thirty-six MDD patients and 30 HV underwent T2-weighted fMRI assessments during the presentation of an implicit affective processing task in three conditions. They differed regarding their affective quality (=valence, high negative, low negative and neutral stimuli) and regarding the arousal based on stimuli from the International Affective Picture System. RESULTS Group contrasts showed lower left-sided activation in dorsolateral prefrontal cortex (DLPFC), anterior PFC, precentral and premotor cortex in PAT compared with HV (Cluster-level threshold, 5000 iterations, p<0.01). We found a significant interaction effect of valence and group, a significant effect of emotional valence and a significant effect of group. All effects were shown in brain regions within the emotional network (Cluster-level threshold, 5000 iterations, p<0.01). Higher arousal (rho=-0.33, p<0.01) and higher valence (rho=-0.33, p<0.01) during high negative stimuli presentation as well as more severe depression (Beck Depression Inventory II [BDI II]; r = 0.39, p = 0.01) were significantly negatively associated with left DLFPC activity in patients. LIMITATIONS Potential influence of psychopharmacological drugs on functional activation is one of the most discussed source of bias in studies with medicated psychiatric patients. CONCLUSIONS The results highlight the importance of left DLPFC during the processing of negative emotional stimuli in MDD. The integration of a neurophysiological model of emotional processing in MDD may help to clarify and improve therapeutic options.
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Affiliation(s)
- M Trettin
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany.
| | - J Dvořák
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany; Brain Imaging Centre, Goethe Univ., Frankfurt/Main, Germany
| | - M Hilke
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - S Wenzler
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany; Brain Imaging Centre, Goethe Univ., Frankfurt/Main, Germany
| | - M Hagen
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - N Ghirmai
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - M Stäblein
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - S Matura
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - A-C Huthmacher
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - D Kraft
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - C Balaban
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - A Ciaramidaro
- University of Modena and Reggio Emilia, Department of Education and Human Sciences
| | - D Prvulovic
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - C Knöchel
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - A Reif
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
| | - V Oertel
- Dept. of Psychiatry, Psychosomatic Medicine and Psychotherapy, Goethe Univ., Frankfurt/Main, Germany
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Hui LS, Munir M, Vuong A, Hilke M, Wong V, Fanchini G, Scharber MC, Sariciftci NS, Turak A. Universal Transfer Printing of Micelle-Templated Nanoparticles Using Plasma-Functionalized Graphene. ACS Appl Mater Interfaces 2020; 12:46530-46538. [PMID: 32940032 PMCID: PMC7564086 DOI: 10.1021/acsami.0c12178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Accepted: 09/17/2020] [Indexed: 06/11/2023]
Abstract
Nanostructure incorporation into devices plays a key role in improving performance, yet processes for preparing two-dimensional (2D) arrays of colloidal nanoparticles tend not to be universally applicable, particularly for soft and oxygen-sensitive substrates for organic and perovskite-based electronics. Here, we show a method of transferring reverse micelle-deposited (RMD) nanoparticles (perovskite and metal oxide) on top of an organic layer, using a functionalized graphene carrier layer for transfer printing. As the technique can be applied universally to RMD nanoparticles, we used magnetic (γ-Fe2O3) and luminescent (methylammonium lead bromide (MAPbBr3)) nanoparticles to validate the transfer-printing methodology. The strong photoluminescence from the MAPbBr3 under UV illumination and high intrinsic field of the γ-Fe2O3 as measured by magnetic force microscopy (MFM), coupled with Raman measurements of the graphene layer, confirm that all components survive the transfer-printing process with little loss of properties. Such an approach to introducing uniform 2D arrays of nanoparticles onto sensitive substrates opens up new avenues to tune the device interfacial properties.
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Affiliation(s)
- Lok Shu Hui
- Department
of Engineering Physics, McMaster University, Hamilton L8S 4L7, Ontario, Canada
| | - Muhammad Munir
- Department
of Engineering Physics, McMaster University, Hamilton L8S 4L7, Ontario, Canada
| | - An Vuong
- Department
of Physics, McGill University, Montreal H3A 2T8, Quebec, Canada
| | - Michael Hilke
- Department
of Physics, McGill University, Montreal H3A 2T8, Quebec, Canada
| | - Victor Wong
- Department
of Physics and Astronomy, University of
Western Ontario, London N6A 3K7, Ontario, Canada
| | - Giovanni Fanchini
- Department
of Physics and Astronomy, University of
Western Ontario, London N6A 3K7, Ontario, Canada
| | - Markus Clark Scharber
- Linz
Institute for Organic Solar Cells (LIOS), Institute of Physical Chemistry, Johannes Kepler University, Linz 4040, Austria
| | - Niyazi Serdar Sariciftci
- Linz
Institute for Organic Solar Cells (LIOS), Institute of Physical Chemistry, Johannes Kepler University, Linz 4040, Austria
| | - Ayse Turak
- Department
of Engineering Physics, McMaster University, Hamilton L8S 4L7, Ontario, Canada
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Elder KLM, Seymour M, Lee M, Hilke M, Provatas N. Two-component structural phase-field crystal models for graphene symmetries. Philos Trans A Math Phys Eng Sci 2018; 376:rsta.2017.0211. [PMID: 29311209 PMCID: PMC5784101 DOI: 10.1098/rsta.2017.0211] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 09/25/2017] [Indexed: 05/25/2023]
Abstract
We extend the three-point XPFC model of Seymour & Provatas (Seymour & Provatas 2016 Phys. Rev. B93, 035447 (doi:10.1103/PhysRevB.93.035447)) to two components to capture chemical vapour deposition-grown graphene, and adapt a previous two-point XPFC model of Greenwood et al. (Greenwood et al. 2011 Phys. Rev. B84, 064104 (doi:10.1103/PhysRevB.84.064104)) into a simple model of two-component graphene. The equilibrium properties of these models are examined and the two models are compared and contrasted. The first model is used to study the possible roles of hydrogen in graphene grain boundaries. The second model is used to study the role of hydrogen in the dendritic growth morphologies of graphene. The latter results are compared with new experiments.This article is part of the theme issue 'From atomistic interfaces to dendritic patterns'.
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Affiliation(s)
- K L M Elder
- Department of Physics, Centre for the Physics of Materials, McGill University, 3600 Rue University, Montreal, Quebec, Canada H3A 2T8
| | - M Seymour
- Department of Physics, Centre for the Physics of Materials, McGill University, 3600 Rue University, Montreal, Quebec, Canada H3A 2T8
| | - M Lee
- Department of Physics, Centre for the Physics of Materials, McGill University, 3600 Rue University, Montreal, Quebec, Canada H3A 2T8
| | - M Hilke
- Department of Physics, Centre for the Physics of Materials, McGill University, 3600 Rue University, Montreal, Quebec, Canada H3A 2T8
| | - N Provatas
- Department of Physics, Centre for the Physics of Materials, McGill University, 3600 Rue University, Montreal, Quebec, Canada H3A 2T8
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6
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Boulanger N, Yu V, Hilke M, Toney MF, Barbero DR. Graphene induced electrical percolation enables more efficient charge transport at a hybrid organic semiconductor/graphene interface. Phys Chem Chem Phys 2018; 20:4422-4428. [DOI: 10.1039/c7cp07871d] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Self-assembly of semiconducting polymer chains during crystallization reveals a percolation induced mechanism of charge transport on graphene, which enhances current and carrier mobility.
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Affiliation(s)
- Nicolas Boulanger
- Nano-Engineered Materials & Organic Electronics Laboratory
- Umeå University
- Umeå
- Sweden
| | - Victor Yu
- Department of Physics
- McGill University
- Montréal
- Canada
| | - Michael Hilke
- Department of Physics
- McGill University
- Montréal
- Canada
| | | | - David R. Barbero
- Nano-Engineered Materials & Organic Electronics Laboratory
- Umeå University
- Umeå
- Sweden
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7
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Boulanger N, Yu V, Hilke M, Toney MF, Barbero DR. In situ probing of the crystallization kinetics of rr-P3HT on single layer graphene as a function of temperature. Phys Chem Chem Phys 2017; 19:8496-8503. [DOI: 10.1039/c6cp08589j] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In situ X-ray diffraction analysis of P3HT films during cooling down on both Si and G.
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Affiliation(s)
- Nicolas Boulanger
- Nano-Engineered Materials and Organic Electronics Laboratory
- Umeå Universitet
- Umeå 90187
- Sweden
| | - Victor Yu
- Department of Physics
- McGill University
- Montréal
- Canada
| | - Michael Hilke
- Department of Physics
- McGill University
- Montréal
- Canada
| | | | - David R. Barbero
- Nano-Engineered Materials and Organic Electronics Laboratory
- Umeå Universitet
- Umeå 90187
- Sweden
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8
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Guermoune A, Hilke M. Fullerenic particles for the growth of carbon nanowall-like flowers on multilayer graphene. Nanotechnology 2016; 27:175603. [PMID: 26987385 DOI: 10.1088/0957-4484/27/17/175603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Carbon nanowalls (CNWs) are composed of stacks of planar graphene layers with open edges that grow almost vertically on a substrate. Their morphology makes them a promising material for field emission, batteries, light absorbers and enhanced detectors for electrochemical and gas sensors. However, three main challenges prevent the fast development of CNWs: the synthesis is energetically demanding, poorly transferable to suitable substrates, and the growth mechanism is not understood. Here, we present a simple method to grow carbon nanowall-like flowers on multilayer graphene through fullerenic particles using thermal CVD and copper. The hydrophobicity of the fabricated hybrid material facilitates its transfer to any substrate. Our findings can boost the understanding of the physical properties and the practical applicability of CNWs. At the same time, our work is a concrete example of the role of multilayer graphene as a platform to one-step synthesis of new transferable graphenic materials.
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Affiliation(s)
- Abdeladim Guermoune
- Department of Physics, McGill University, 3600 University Street, Montreal, QC, H3A 2T8, Canada
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9
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Yang W, Zhang Y, Hilke M, Reisner W. Dynamic imaging of Au-nanoparticles via scanning electron microscopy in a graphene wet cell. Nanotechnology 2015; 26:315703. [PMID: 26177916 DOI: 10.1088/0957-4484/26/31/315703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
High resolution nanoscale imaging in liquid environments is crucial for studying molecular interactions in biological and chemical systems. In particular, electron microscopy is the gold-standard tool for nanoscale imaging, but its high-vacuum requirements make application to in-liquid samples extremely challenging. Here we present a new graphene based wet cell device where high resolution scanning electron microscope (SEM) and energy dispersive x-rays (EDX) analysis can be performed directly inside a liquid environment. Graphene is an ideal membrane material as its high transparancy, conductivity and mechanical strength can support the high vacuum and grounding requirements of a SEM while enabling maximal resolution and signal. In particular, we obtain high resolution ([Formula: see text] nm) SEM video images of nanoparticles undergoing Brownian motion inside the graphene wet cell and EDX analysis of nanoparticle composition in the liquid enviornment. Our obtained resolution surpasses current conventional silicon nitride devices imaged in both a SEM and transmission electron microscope under much higher electron doses.
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Affiliation(s)
- Wayne Yang
- Department of Physics and RQMP, McGill University, Montreal, Canada
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10
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Buron JD, Petersen DH, Bøggild P, Cooke DG, Hilke M, Sun J, Whiteway E, Jessen BS, Nielsen PF, Hansen O, Yurgens A, Jepsen PU. Correction to graphene uniformity conductance mapping. Nano Lett 2015; 15:803. [PMID: 25470179 DOI: 10.1021/nl504550p] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
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11
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Buron JD, Pizzocchero F, Jessen BS, Booth TJ, Nielsen PF, Hansen O, Hilke M, Whiteway E, Jepsen PU, Bøggild P, Petersen DH. Electrically continuous graphene from single crystal copper verified by terahertz conductance spectroscopy and micro four-point probe. Nano Lett 2014; 14:6348-6355. [PMID: 25317778 DOI: 10.1021/nl5028167] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The electrical performance of graphene synthesized by chemical vapor deposition and transferred to insulating surfaces may be compromised by extended defects, including for instance grain boundaries, cracks, wrinkles, and tears. In this study, we experimentally investigate and compare the nano- and microscale electrical continuity of single layer graphene grown on centimeter-sized single crystal copper with that of previously studied graphene films, grown on commercially available copper foil, after transfer to SiO2 surfaces. The electrical continuity of the graphene films is analyzed using two noninvasive conductance characterization methods: ultrabroadband terahertz time-domain spectroscopy and micro four-point probe, which probe the electrical properties of the graphene film on different length scales, 100 nm and 10 μm, respectively. Ultrabroadband terahertz time-domain spectroscopy allows for measurement of the complex conductance response in the frequency range 1-15 terahertz, covering the entire intraband conductance spectrum, and reveals that the conductance response for the graphene grown on single crystalline copper intimately follows the Drude model for a barrier-free conductor. In contrast, the graphene grown on commercial copper foil shows a distinctly non-Drude conductance spectrum that is better described by the Drude-Smith model, which incorporates the effect of preferential carrier backscattering associated with extended, electronic barriers with a typical separation on the order of 100 nm. Micro four-point probe resistance values measured on graphene grown on single crystalline copper in two different voltage-current configurations show close agreement with the expected distributions for a continuous 2D conductor, in contrast with previous observations on graphene grown on commercial copper foil. The terahertz and micro four-point probe conductance values of the graphene grown on single crystalline copper shows a close to unity correlation, in contrast with those of the graphene grown on commercial copper foil, which we explain by the absence of extended defects on the microscale in CVD graphene grown on single crystalline copper. The presented results demonstrate that the graphene grown on single crystal copper is electrically continuous on the nanoscopic, microscopic, as well as intermediate length scales.
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Affiliation(s)
- Jonas D Buron
- DTU Nanotech, Technical University of Denmark , Ørsteds Plads 345E, Kongens Lyngby 2800, Denmark
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12
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Abstract
High temperature deposition of graphene on Cu by chemical vapor deposition can be used to produce high quality films. However, these films tend to have a non-equilibrium structure, with relatively low graphene adhesion. In this study, samples of graphene grown on copper foils by high temperature CVD were post-deposition annealed at temperatures well below the critical temperature of Cu. Resistance to etching under plasma was examined to assess the mechanical robustness of the graphene on the Cu surface, analyzed using optical and Raman microscopies. We found a correlation between the post-annealing time and etching time for the complete removal of graphene from Cu. Etching rates, minimum etch times, and surface appearance were observed to vary depending on the etching plasma (air, oxygen or nitrogen). Oxygen plasmas were found to be the least aggressive, emphasizing the improved adhesion with post-annealing treatments. Our results imply that the etching of graphene on Cu, and hence the adhesion of graphene, can be controlled by proper annealing and choice of plasma gas.
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Affiliation(s)
- L. S. Hui
- Department of Engineering Physics
- McMaster University
- Hamilton, Canada
| | - E. Whiteway
- Department of Physics
- McGill University
- Montréal, Canada
| | - M. Hilke
- Department of Physics
- McGill University
- Montréal, Canada
| | - A. Turak
- Department of Engineering Physics
- McMaster University
- Hamilton, Canada
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13
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Massicotte M, Yu V, Whiteway E, Vatnik D, Hilke M. Quantum Hall effect in fractal graphene: growth and properties of graphlocons. Nanotechnology 2013; 24:325601. [PMID: 23863353 DOI: 10.1088/0957-4484/24/32/325601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Highly dendritic graphene crystals up to 0.25 mm in diameter are synthesized by low pressure chemical vapor deposition inside a copper enclosure. With their six-fold symmetry and fractal-like shape, the crystals resemble snowflakes. The evolution of the dendritic growth features is investigated for different growth conditions, and surface diffusion is found to be the growth-limiting step responsible for the formation of dendrites. The electronic properties of the dendritic crystals are examined down to sub-Kelvin temperatures, showing a mobility of up to 6300 cm(2) V(-1) s(-1) and quantum Hall oscillations are observed above 4 T. These results demonstrate the high quality of the transport properties despite their rough dendritic edges.
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Affiliation(s)
- Mathieu Massicotte
- Department of Physics, McGill University, Montréal, QC, H3A 2T8, Canada.
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14
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Buron JD, Petersen DH, Bøggild P, Cooke DG, Hilke M, Sun J, Whiteway E, Nielsen PF, Hansen O, Yurgens A, Jepsen PU. Graphene conductance uniformity mapping. Nano Lett 2012; 12:5074-5081. [PMID: 22947167 DOI: 10.1021/nl301551a] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We demonstrate a combination of micro four-point probe (M4PP) and non-contact terahertz time-domain spectroscopy (THz-TDS) measurements for centimeter scale quantitative mapping of the sheet conductance of large area chemical vapor deposited graphene films. Dual configuration M4PP measurements, demonstrated on graphene for the first time, provide valuable statistical insight into the influence of microscale defects on the conductance, while THz-TDS has potential as a fast, non-contact metrology method for mapping of the spatially averaged nanoscopic conductance on wafer-scale graphene with scan times of less than a minute for a 4-in. wafer. The combination of M4PP and THz-TDS conductance measurements, supported by micro Raman spectroscopy and optical imaging, reveals that the film is electrically continuous on the nanoscopic scale with microscopic defects likely originating from the transfer process, dominating the microscale conductance of the investigated graphene film.
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Affiliation(s)
- Jonas D Buron
- Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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15
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Cooper DR, D’Anjou B, Ghattamaneni N, Harack B, Hilke M, Horth A, Majlis N, Massicotte M, Vandsburger L, Whiteway E, Yu V. Experimental Review of Graphene. ACTA ACUST UNITED AC 2012. [DOI: 10.5402/2012/501686] [Citation(s) in RCA: 337] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This review examines the properties of graphene from an experimental perspective. The intent is to review the most important experimental results at a level of detail appropriate for new graduate students who are interested in a general overview of the fascinating properties of graphene. While some introductory theoretical concepts are provided, including a discussion of the electronic band structure and phonon dispersion, the main emphasis is on describing relevant experiments and important results as well as some of the novel applications of graphene. In particular, this review covers graphene synthesis and characterization, field-effect behavior, electronic transport properties, magnetotransport, integer and fractional quantum Hall effects, mechanical properties, transistors, optoelectronics, graphene-based sensors, and biosensors. This approach attempts to highlight both the means by which the current understanding of graphene has come about and some tools for future contributions.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Victor Yu
- McGill University, Montréal, QC, Canada H3A 2T8
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16
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Lefebvre J, Hilke M, Altounian Z. Strengthening of reentrant pinning by collective interactions in the peak effect. Phys Rev Lett 2009; 102:257002. [PMID: 19659112 DOI: 10.1103/physrevlett.102.257002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Indexed: 05/28/2023]
Abstract
Since it was first observed about 40 years ago [A. B. Pippard, Proc. R. Soc. A 216, 547 (1953)10.1098/rspa.1953.0040], the peak effect has been the subject of extensive research mainly impelled by the desire to determine its exact mechanisms. Despite these efforts, a consensus on this question has yet to be reached. Experimentally, the peak effect indicates a transition from a depinned vortex phase to a reentrant pinning phase at a high magnetic field. To study the effects of intrinsic pinning on the peak effect, we consider FexNi1-xZr2 superconducting metallic glasses in which the vortex pinning force varies depending on the Fe content and in which a huge peak effect is seen. The results show that the peak effect broadens with decreasing pinning force. Typically, pinning is increased by pinning centers, but here we show that reentrant pinning is due to the strengthening of interactions and collective effects (while decreasing pinning strength).
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Affiliation(s)
- J Lefebvre
- Department of Physics, McGill University, Montréal, Canada H3A 2T8
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17
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Hilke M. Noninteracting electrons and the metal-insulator transition in two dimensions with correlated impurities. Phys Rev Lett 2003; 91:226403. [PMID: 14683259 DOI: 10.1103/physrevlett.91.226403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2003] [Indexed: 05/24/2023]
Abstract
While standard scaling arguments show that a system of noninteracting electrons in two dimensions and in the presence of uncorrelated disorder is insulating, in this paper we discuss the case where interimpurity correlations are included. We find that for pointlike impurities and an infinite interimpurity correlation length, a mobility edge exists in 2D even if the individual impurity potentials are random. In the uncorrelated system we recover the scaling results, while in the intermediate regime for length scales comparable to the correlation length, the system behaves like a metal but with increasing fluctuations, before strong localization eventually takes over for length scales much larger than the correlation length. In the intermediate regime, the relevant length scale is given by the interimpurity correlation length, with important consequences for high mobility systems.
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Affiliation(s)
- M Hilke
- Department of Physics, McGill University, Montréal, Quebec, Canada H3A 2T8.
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Hilke M, Reid S, Gagnon R, Altounian Z. Peak Effect and the Phase Diagram of Moving Vortices in FexNi1-xZr2 Superconducting Glasses. Phys Rev Lett 2003; 91:127004. [PMID: 14525392 DOI: 10.1103/physrevlett.91.127004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2003] [Indexed: 05/24/2023]
Abstract
In the mixed state of type II superconductors, vortices penetrate the sample and form a correlated system due to the screening of supercurrents around them. Interestingly, we can study this correlated system as a function of density and driving force. The density, for instance, is controlled by the magnetic field B, whereas a current density j acts as a driving force F=j x B on all vortices. To minimize the pinning strength, we study a superconducting glass in which the depinning current is 10 to 1000 times smaller than in previous studies, which enables us to map out the complete phase diagram in this new regime. The diagram is obtained as a function of B, driving current, and temperature, and leads to a remarkable set of new results, which includes a huge peak effect, an additional reentrant depinning phase, and a driving force induced pinning phase.
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Affiliation(s)
- M Hilke
- Department of Physics, McGill University, Montréal, Canada H3A 2T8.
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