Andrew McRae, Ph.D. student
Strain-engineering of electron transport in SWCNTs and graphene
Champagne Research Group
Nano-scale quantum electronics and mechanics
Atomic scale Mechanical Breakjunction
We specialize in:
- experimental nano-scale and mesoscopic physics
- electron transport and heat transport in carbon, metallic and semiconducting systems
- nano-resonators and sensors (NEMS)
- quantum mechanics of strongly correlated electron systems
Part of the widespread interest in nanometer-sized systems is motivated by their capability to combine and hybridize mechanical and electronic properties of materials at the nanoscale. The long term goals of our research are to understand at a fundamental level, and harness into applications, the interplays of structure, electronic degrees of freedom, and correlated electronic phases in nano and mesoscopic systems.
Four specific projects on which we are currently working are: (1) Quantum electronic properties of nanosystems under strain, (2) Heat transport in graphene (relativistic-like electrons), (3) Nano-electro-mechanical sensors (NEMS) based on carbon nanotubes and graphene, (4) Electronic and magnetic properties of Topological Insulators.
Our work focuses on graphene (both a single-molecule and a 2-dimensional electron gas where electrons behave like relativistic particles), carbon nanotubes (1-d nanosystems), and topological insulators which are ideal testing grounds for the interplays of mechanical degrees of freedom with electrons and their many body-states.
A suspended g-MCBJ. We electromigate the junction to connect single molecules and study their electronic spectrum.
We make use of a low temperature gated-mechanical breakjunction system (see Figure), which can controllably stress a nanosystem to tune its shape and strain, while simultaneously making detailed transport measurements. We want to understand how the interplays between structure (lattice, defects, shape, strain, boundaries, phonons) and electronic interactions (Coulomb interactions, screening, charged excitations) determine the properties of nanosystems (scattering, band structure, ground states, coherence, excited states).
A suspended carbon nanotube inside a gated-Mechanical Breakjunction (g-MCBJ)
Heat transport measures the energy carried by both electrons and phonons and is fundamental to understanding a material, its ground states, excitations and scattering mechanisms.
Image of a 1 micron long suspended graphene(one-atom thick) crystal.
Measurements of thermal conductivity and thermopower over a broad temperature range (1.5-300 Kelvin) will assess graphene's promising potential for thermal management in nanoscale electronics. We also aim to test the theoretical models of heat propagation in graphene, its phonon modes and their scattering mechanisms, as well as heat transport in the quantum Hall regime.
Optical image of micron scale heater and thermometers on a graphene flake.
We are fabricating nanometer-size few-layer thick graphene nanoribbons or carbon nanotubes oscillators. Using a low-temperature mechanical breakjunction system, we will study their potential as tunable ultra-high frequency nano-electro-mechanical systems (NEMS), and we expect these very short ribbons to have resonant frequencies in the THz range.
These NEMS will make very sensitive nanoscale sensors, since even a very small force or mass on the oscillator will cause a shift of its resonant frequency. We also want to use these sensors as laboratories to explore the physics of carbon nanotube and graphene quantum dots.
Cartoon of electron transport in a quantum dot nano-oscillators
In collaboration with the group of Prof. Oussama Moutanabbir (Ecole Polytechnique), we investigate how engineered defects (stacking faults) in silicon nanowires (Si-NWs) affect charge carrier and phonon transport. We study individual Si-NWs grown by the VLS method (Moutanabbir), see Figure, with ordered lattice defect planes along the growth direction. Characterization of the Si-NWs is done by micro-Raman spectroscopy which is sensitive to the presence of crystal faults. Transport and magneto-transport measurements are done at low temperature in single suspended Si-NWs transistors. We are interested in exploring fundamental quantum transport in Si-NW quantum dots, as well as their application in thermal energy harvesting. The thermal conductivity, K, of Si-NWs is lower than for bulk silicon. Defect and surface engineering of Si-NWs can further reduce K, improving the thermoelectric efficiency (ability to harvest energy) to maximizing the figure of merit ZT = (S^2)*sigma*T/K. This would have applications in industry such as improving thermocouples to gather more thermal energy from vapor exhausts.
Left panel, high-resolution TEM image of a Si-NW crystal’s structure showing stacking faults along the growth direction. Right panel, SEM image of our Si-NWs grown by the VLS method (O. Moutanabbir).
Andrew McRae, Ph.D. student
Marc Collette, Ph.D. student
Charge and thermal transport in defect-engineered silicon nanowires
Gareth Melin, M.Sc. student, so-supervised with Dr. Valter Zazubovits
Electro-optics of graphene
Matthew Storms, M.Sc. student
High-Frequency electron transport in carbon NEMS
Guoqing Wei, M.Sc. student
Graphene Quantum Strain Transistors
Israel Gomez Rebollo , M.Sc. student
Electro-optics of graphene/boron-nitride heterostructures
Wyatt Wright, B.Sc.
Michaël Bertaud-Rainville, B.Sc. (2017)
Fernanda Cristina Rodrigues Machado, B.Sc. (2017), Concordia USRA student
Simon-Gabriel Beauvais, B.Sc.-Coop intern (2015-16), now a MSc student at U. de Montreal
Serap Yigen M.Sc. (2010) PhD (2015)
James M.Sc.(2015) - now a Ph.D. student in Bioengineering at McGill
Patrick Janeiro B.Sc.(2015) - now a researcher at nuance Communications)
Vahid Tayari, Ph.D. (2014) - now, postdoc with T. Szkopek at McGill
Dhan Cardinal, B.Sc. (2013)
Colleen Kinross, B.Sc., NSERC-USRA (2013)
Andrew McRae, M.Sc. (2013)
Dr. Ying Liu (2012)
Joshua Island, M.Sc.(2011) - now, Ph.D. with H. van der Zant, TU Delft
Serap Yigen, M.Sc. (2010)
Adam Michaels, B.Sc (2012)
Matthew Sarrasin, B.Sc,PHYS 497 (2011)
James Porter, B.Sc, NSERC-USRA and PHYS 497 (2011)
Roopak Singh, B.Sc (2010)
Vincent Grenier, B.Sc, SCOL 290 (2010)
Maryam Tabatabaei, B.Sc (2009)
Champagne Group (Dec 2013)
Champagne Group (August 2010)
Our laboratory in located in the basement of the Science Pavillion on the Loyola campus. It is a brand new 65 square-meter laboratory space with a low vibration floor, 5 meter high ceiling, sound proofed pump and service room, fume hood, gas (He, N, compressed air) and vacuum service all around the lab, as well as 2 electrical panels with isolated grounds. We have two low-temperature cryostats, a chemical vapor deposition growth chamber, and many other toys.
North side of the lab.
Clean room facilities
We make use of a broad array of micro- and nano-fabrication tools at open access clean room facilities located at the Ecole Polytechnique and McGill University in Montreal
Nanoscience Group facilities
Our group is a member of the Nanoscience Group at Concordia which shares a large number of facilities
Instruments located in our lab
Cryogen-free He-3 top-loading VTI cryostat with 9 Tesla magnet
Low-temperature cryostat (0.3 - 300 Kelvin). Allows a wide range of electron transport experiments in nanosystems as a function of temperature, electric and magnetic field.
Variable temperature cryostat (VTI)
Low-temperature cryostat (1.5 - 420 Kelvin). Allows a wide range of electron transport experiments in nanosystems as a function of temperature, electric and magnetic field.
Mechanical breakjunction cryostat (MBJ)
Low-temperature cryostat (4.2 - 300 Kelvin) equipped with a mechanical breakjunction assembly. Allows a wide range of electron transport experiments in nanosystems as a function of mechanical strain.
14 Tesla superconducting magnet
14 Tesla magnet and its dewar which can be used with both cryostats (VTI and MBJ).
Electrical probe station
Five-probe probe station for sample characterization during microfabrication.
Four-source thermal evaporator for thin film depostions.
Chemical vapor deposition system (CVD)
Gas flowmeters and furnace making up the CVD. The CVD is used for the growth of single-wall carbon nanotubes (SWCNT) and microcrystals of topological insulators (Bi2Se3).
Helium leak detector and turbo-pumping station
High precision helium-3 and helium-4 leak detector equipped with a turbo-molecular pump. An additional high-volume turbo-pumping station is used for high vacuum pumping. Permits the operation and maintenance of helium-3 and helium-4 low-temperature cryostats.
High resolution Olympus BX51 optical microscope and XC-50 color digital camera system. Allows easy identification of graphene (carbon monolayer) crystals and characterization of micro-lithography.
- Mcrae, A., Wei, G. & Champagne, A. Graphene Quantum Strain Transistors. Bulletin of the American Physical Society (2018).
- Collette, M., Moutanabbir, O. & Champagne, A. Conductivity Measurements in Hexagonal-Core Silicon Nanowire Transistors. Bulletin of the American Physical Society (2018).
- A.C. McRae, V. Tayari, J. M. Porter, and A R. Champagne, Giant electron-hole transport asymmetry in ultra-short quantum transistors, Nature Communications 8, 15491 (2017). PDF Supplementary Information
- V. Tayari, A. C. McRae, S. Yigen, J. O. Island, J. M. Porter, and A. R. Champagne, Tailoring 10 nm Scale Suspended Graphene Junctions and Quantum Dots , Nano Letters, 15; 114 (2015). PDF
- S. Yigen, and A. R. Champagne, Wiedemann-Franz Relation and Thermal-transistor Effect in Suspended Graphene, Nano Letters, 14; 289 (2014). PDF Supplemental Online Information
- S. Yigen, V. Tayari, J. O. Island, J. M. Porter, and A. R. Champagne, Electronic Thermal Conductivity Measurements in Intrinsic Graphene, Physical Review B, 87; 241411(R)(2013) PDF Supplemental Information
- J. O. Island, V. Tayari, A. C. McRae, and A. R. Champagne, Few-hundred GHz Carbon Nanotube NEMS, Nano Letters, 12; 4564 (2012) PDF Supporting Information
- J. O. Island, V. Tayari, S. Yigen, A. C. McRae, and A. R. Champagne, Ultra-short suspended single-wall carbon nanotube transistors, Applied Physics Letters, 99; 243106 (2011) PDF
Press coverage: featured in the Virtual Journal of Nanoscience and Technology
- J. J. Parks, A. R. Champagne, T. A. Costi, W. W. Shum, A. N. Pasupathy, E. Neuscamman, S. Flores-Torres, P. S. Cornaglia, A. A. Aligia, C. A. Balseiro, G. K.-L. Chan, H. D. Abruña, and D. C. Ralph, Mechanical control of spin states in spin-1 molecules and the underscreened Kondo effect, Science, 328; 1370 (2010) PDF Supporting Information
Press coverage: featured in Science and Nature Nanotechnology and many other press releases.
- A. D. K. Finck, A. R. Champagne, J. P. Eisenstein, L. N. Pfeiffer and K. W. West, Area Dependence of Interlayer Tunneling in Strongly Correlated Bilayer Two-Dimensional Electron Systems at νT=1, Physical Review B, 78; 075302(2008) PDF
Press coverage: featured in Physics
- A. R. Champagne, A. D. K. Finck, J. P. Eisenstein, L. N. Pfeiffer and K. W. West, Charge Imbalance and Bilayer Two-Dimensional Electron Systems at νT=1, Physical Review B, 78; 205310(2008) PDF
Press coverage: featured in Physics
- A. R. Champagne, J. P. Eisenstein, L. N. Pfeiffer and K. W. West, Evidence for a Finite-Temperature Phase Transition in a Bilayer Quantum Hall System, Physical Review Letters, 100; 096801(2008) PDF
- J. J. Parks, A. R. Champagne, G. R. Hutchison, S. Flores-Torres, H. D. Abruna and D. C. Ralph, Tuning the Kondo Effect with a Mechanically Controllable Break Junction, Physical Review Letters, 99; 026601(2007) PDF
Press coverage: featured in Nature Nanotechnology
- A. R. Champagne, A. N. Pasupathy and D. C. Ralph, Mechanically Adjustable and Electrically Gated Single-Molecule Transistors, Nano Letters, 5; 305(2005) PDF
- A. R. Champagne, A. J. Couture, F. Kuemmeth and D. C. Ralph, Nanometer-Scale Scanning Sensors Fabricated Using Stencil Lithography, Applied Physics Letters, 82; 1111(2003) PDF