Andre Geim
Degree: PhD
Position: Distinguished Visiting Professor
Affiliation: University of Manchester
Research Type: Experiment
Email: geim@manchester.ac.uk
Website: http://www.condmat.physics.manchester.ac.uk/people/academic/geim/
CA2DM Publications:
2021 |
Xu, Shuigang; Ezzi, Mohammed Al M; Balakrishnan, Nilanthy; Garcia-Ruiz, Aitor; Tsim, Bonnie; Mullan, Ciaran; Barrier, Julien; Xin, Na; Piot, Benjamin A; Taniguchi, Takashi; Watanabe, Kenji; Carvalho, Alexandra; Mishchenko, Artem; Geim, A K; Fal'ko, Vladimir I; Adam, Shaffique; Neto, Antonio Helio Castro; Novoselov, Kostya S; Shi, Yanmeng Tunable van Hove singularities and correlated states in twisted monolayer-bilayer graphene Journal Article NATURE PHYSICS, 17 (5), pp. 619-+, 2021, ISSN: 1745-2473. @article{ISI:000619417000001, title = {Tunable van Hove singularities and correlated states in twisted monolayer-bilayer graphene}, author = {Shuigang Xu and Mohammed Al M Ezzi and Nilanthy Balakrishnan and Aitor Garcia-Ruiz and Bonnie Tsim and Ciaran Mullan and Julien Barrier and Na Xin and Benjamin A Piot and Takashi Taniguchi and Kenji Watanabe and Alexandra Carvalho and Artem Mishchenko and A K Geim and Vladimir I Fal'ko and Shaffique Adam and Antonio Helio Castro Neto and Kostya S Novoselov and Yanmeng Shi}, doi = {10.1038/s41567-021-01172-9}, times_cited = {0}, issn = {1745-2473}, year = {2021}, date = {2021-02-18}, journal = {NATURE PHYSICS}, volume = {17}, number = {5}, pages = {619-+}, publisher = {NATURE RESEARCH}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Understanding and tuning correlated states is of great interest and importance to modern condensed-matter physics. The recent discovery of unconventional superconductivity and Mott-like insulating states in magic-angle twisted bilayer graphene presents a unique platform to study correlation phenomena, in which the Coulomb energy dominates over the quenched kinetic energy as a result of hybridized flat bands. Extending this approach to the case of twisted multilayer graphene would allow even higher control over the band structure because of the reduced symmetry of the system. Here we study electronic transport properties of twisted monolayer-bilayer graphene (a bilayer on top of monolayer graphene heterostructure). We observe the formation of van Hove singularities that are highly tunable by changing either the twist angle or external electric field and can cause strong correlation effects under optimum conditions. We provide basic theoretical interpretations of the observed electronic structure.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Understanding and tuning correlated states is of great interest and importance to modern condensed-matter physics. The recent discovery of unconventional superconductivity and Mott-like insulating states in magic-angle twisted bilayer graphene presents a unique platform to study correlation phenomena, in which the Coulomb energy dominates over the quenched kinetic energy as a result of hybridized flat bands. Extending this approach to the case of twisted multilayer graphene would allow even higher control over the band structure because of the reduced symmetry of the system. Here we study electronic transport properties of twisted monolayer-bilayer graphene (a bilayer on top of monolayer graphene heterostructure). We observe the formation of van Hove singularities that are highly tunable by changing either the twist angle or external electric field and can cause strong correlation effects under optimum conditions. We provide basic theoretical interpretations of the observed electronic structure. |
Woods, C R; Ares, P; Nevison-Andrews, H; Holwill, M J; Fabregas, R; Guinea, F; Geim, A K; Novoselov, K S; Walet, N R; Fumagalli, L Charge-polarized interfacial superlattices in marginally twisted hexagonal boron nitride Journal Article NATURE COMMUNICATIONS, 12 (1), 2021, ISSN: 2041-1723. @article{ISI:000662813400002, title = {Charge-polarized interfacial superlattices in marginally twisted hexagonal boron nitride}, author = {C R Woods and P Ares and H Nevison-Andrews and M J Holwill and R Fabregas and F Guinea and A K Geim and K S Novoselov and N R Walet and L Fumagalli}, doi = {10.1038/s41467-020-20667-2}, times_cited = {6}, issn = {2041-1723}, year = {2021}, date = {2021-01-12}, journal = {NATURE COMMUNICATIONS}, volume = {12}, number = {1}, publisher = {NATURE RESEARCH}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {When two-dimensional crystals are brought into close proximity, their interaction results in reconstruction of electronic spectrum and crystal structure. Such reconstruction strongly depends on the twist angle between the crystals, which has received growing attention due to interesting electronic and optical properties that arise in graphene and transitional metal dichalcogenides. Here we study two insulating crystals of hexagonal boron nitride stacked at small twist angle. Using electrostatic force microscopy, we observe ferroelectric-like domains arranged in triangular superlattices with a large surface potential. The observation is attributed to interfacial elastic deformations that result in out-of-plane dipoles formed by pairs of boron and nitrogen atoms belonging to opposite interfacial surfaces. This creates a bilayer-thick ferroelectric with oppositely polarized (BN and NB) dipoles in neighbouring domains, in agreement with our modeling. These findings open up possibilities for designing van der Waals heterostructures and offer an alternative probe to study moire-superlattice electrostatic potentials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When two-dimensional crystals are brought into close proximity, their interaction results in reconstruction of electronic spectrum and crystal structure. Such reconstruction strongly depends on the twist angle between the crystals, which has received growing attention due to interesting electronic and optical properties that arise in graphene and transitional metal dichalcogenides. Here we study two insulating crystals of hexagonal boron nitride stacked at small twist angle. Using electrostatic force microscopy, we observe ferroelectric-like domains arranged in triangular superlattices with a large surface potential. The observation is attributed to interfacial elastic deformations that result in out-of-plane dipoles formed by pairs of boron and nitrogen atoms belonging to opposite interfacial surfaces. This creates a bilayer-thick ferroelectric with oppositely polarized (BN and NB) dipoles in neighbouring domains, in agreement with our modeling. These findings open up possibilities for designing van der Waals heterostructures and offer an alternative probe to study moire-superlattice electrostatic potentials. |
2020 |
Shi, Yanmeng; Xu, Shuigang; Yang, Yaping; Slizovskiy, Sergey; Morozov, Sergey V; Son, Seok-Kyun; Ozdemir, Servet; Mullan, Ciaran; Barrier, Julien; Yin, Jun; Berdyugin, Alexey I; Piot, Benjamin A; Taniguchi, Takashi; Watanabe, Kenji; Fal'ko, Vladimir I; Novoselov, Kostya S; Geim, A K; Mishchenko, Artem Electronic phase separation in multilayer rhombohedral graphite Journal Article NATURE, 584 (7820), pp. 210-+, 2020, ISSN: 0028-0836. @article{ISI:000559831500011, title = {Electronic phase separation in multilayer rhombohedral graphite}, author = {Yanmeng Shi and Shuigang Xu and Yaping Yang and Sergey Slizovskiy and Sergey V Morozov and Seok-Kyun Son and Servet Ozdemir and Ciaran Mullan and Julien Barrier and Jun Yin and Alexey I Berdyugin and Benjamin A Piot and Takashi Taniguchi and Kenji Watanabe and Vladimir I Fal'ko and Kostya S Novoselov and A K Geim and Artem Mishchenko}, doi = {10.1038/s41586-020-2568-2}, times_cited = {0}, issn = {0028-0836}, year = {2020}, date = {2020-08-13}, journal = {NATURE}, volume = {584}, number = {7820}, pages = {210-+}, publisher = {NATURE RESEARCH}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Of the two stable forms of graphite, hexagonal and rhombohedral, the former is more common and has been studied extensively. The latter is less stable, which has so far precluded its detailed investigation, despite many theoretical predictions about the abundance of exotic interaction-induced physics(1-6). Advances in van der Waals heterostructure technology(7)have now allowed us to make high-quality rhombohedral graphite films up to 50 graphene layers thick and study their transport properties. Here we show that the bulk electronic states in such rhombohedral graphite are gapped(8)and, at low temperatures, electron transport is dominated by surface states. Because of their proposed topological nature, the surface states are of sufficiently high quality to observe the quantum Hall effect, whereby rhombohedral graphite exhibits phase transitions between a gapless semimetallic phase and a gapped quantum spin Hall phase with giant Berry curvature. We find that an energy gap can also be opened in the surface states by breaking their inversion symmetry by applying a perpendicular electric field. Moreover, in rhombohedral graphite thinner than four nanometres, a gap is present even without an external electric field. This spontaneous gap opening shows pronounced hysteresis and other signatures characteristic of electronic phase separation, which we attribute to emergence of strongly correlated electronic surface states.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Of the two stable forms of graphite, hexagonal and rhombohedral, the former is more common and has been studied extensively. The latter is less stable, which has so far precluded its detailed investigation, despite many theoretical predictions about the abundance of exotic interaction-induced physics(1-6). Advances in van der Waals heterostructure technology(7)have now allowed us to make high-quality rhombohedral graphite films up to 50 graphene layers thick and study their transport properties. Here we show that the bulk electronic states in such rhombohedral graphite are gapped(8)and, at low temperatures, electron transport is dominated by surface states. Because of their proposed topological nature, the surface states are of sufficiently high quality to observe the quantum Hall effect, whereby rhombohedral graphite exhibits phase transitions between a gapless semimetallic phase and a gapped quantum spin Hall phase with giant Berry curvature. We find that an energy gap can also be opened in the surface states by breaking their inversion symmetry by applying a perpendicular electric field. Moreover, in rhombohedral graphite thinner than four nanometres, a gap is present even without an external electric field. This spontaneous gap opening shows pronounced hysteresis and other signatures characteristic of electronic phase separation, which we attribute to emergence of strongly correlated electronic surface states. |
2019 |
Wang, Zihao; Wang, Yi Bo; Yin, J; Tovari, E; Yang, Y; Lin, L; Holwill, M; Birkbeck, J; Perello, D J; Xu, Shuigang; Zultak, J; Gorbachev, R V; Kretinin, A V; Taniguchi, T; Watanabe, K; Morozov, S V; Andelkovic, M; Milovanovic, S P; Covaci, L; Peeters, F M; Mishchenko, A; Geim, A K; Novoselov, K S; Fal'ko, Vladimir I; Knothe, Angelika; Woods, C R Composite super-moire lattices in double-aligned graphene heterostructures Journal Article SCIENCE ADVANCES, 5 (12), 2019, ISSN: 2375-2548. @article{ISI:000505069600089, title = {Composite super-moire lattices in double-aligned graphene heterostructures}, author = {Zihao Wang and Yi Bo Wang and J Yin and E Tovari and Y Yang and L Lin and M Holwill and J Birkbeck and D J Perello and Shuigang Xu and J Zultak and R V Gorbachev and A V Kretinin and T Taniguchi and K Watanabe and S V Morozov and M Andelkovic and S P Milovanovic and L Covaci and F M Peeters and A Mishchenko and A K Geim and K S Novoselov and Vladimir I Fal'ko and Angelika Knothe and C R Woods}, doi = {10.1126/sciadv.aay8897}, times_cited = {0}, issn = {2375-2548}, year = {2019}, date = {2019-12-01}, journal = {SCIENCE ADVANCES}, volume = {5}, number = {12}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, address = {1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA}, abstract = {When two-dimensional (2D) atomic crystals are brought into close proximity to form a van der Waals heterostructure, neighbouring crystals may influence each other's properties. Of particular interest is when the two crystals closely match and a moire pattern forms, resulting in modified electronic and excitonic spectra, crystal reconstruction, and more. Thus, moire patterns are a viable tool for controlling the properties of 2D materials. However, the difference in periodicity of the two crystals limits the reconstruction and, thus, is a barrier to the low-energy regime. Here, we present a route to spectrum reconstruction at all energies. By using graphene which is aligned to two hexagonal boron nitride layers, one can make electrons scatter in the differential moire pattern which results in spectral changes at arbitrarily low energies. Further, we demonstrate that the strength of this potential relies crucially on the atomic reconstruction of graphene within the differential moire super cell.}, keywords = {}, pubstate = {published}, tppubtype = {article} } When two-dimensional (2D) atomic crystals are brought into close proximity to form a van der Waals heterostructure, neighbouring crystals may influence each other's properties. Of particular interest is when the two crystals closely match and a moire pattern forms, resulting in modified electronic and excitonic spectra, crystal reconstruction, and more. Thus, moire patterns are a viable tool for controlling the properties of 2D materials. However, the difference in periodicity of the two crystals limits the reconstruction and, thus, is a barrier to the low-energy regime. Here, we present a route to spectrum reconstruction at all energies. By using graphene which is aligned to two hexagonal boron nitride layers, one can make electrons scatter in the differential moire pattern which results in spectral changes at arbitrarily low energies. Further, we demonstrate that the strength of this potential relies crucially on the atomic reconstruction of graphene within the differential moire super cell. |
2017 |
Esfandiar, A; Radha, B; Wang, F C; Yang, Q; Hu, S; Garaj, S; Nair, R R; Geim, A K; Gopinadhan, K Size effect in ion transport through angstrom-scale slits Journal Article SCIENCE, 358 (6362), pp. 511-513, 2017, ISSN: 0036-8075. @article{ISI:000413757500042, title = {Size effect in ion transport through angstrom-scale slits}, author = {A Esfandiar and B Radha and F C Wang and Q Yang and S Hu and S Garaj and R R Nair and A K Geim and K Gopinadhan}, doi = {10.1126/science.aan5275}, times_cited = {0}, issn = {0036-8075}, year = {2017}, date = {2017-10-27}, journal = {SCIENCE}, volume = {358}, number = {6362}, pages = {511-513}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, address = {1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA}, abstract = {In the field of nanofluidics, it has been an ultimate but seemingly distant goal to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying the effects of angstrom-scale confinement, which is important for the development of nanofluidics, molecular separation, and other nanoscale technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the field of nanofluidics, it has been an ultimate but seemingly distant goal to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying the effects of angstrom-scale confinement, which is important for the development of nanofluidics, molecular separation, and other nanoscale technologies. |
2014 |
Kretinin, A V; Cao, Y; Tu, J S; Yu, G L; Jalil, R; Novoselov, K S; Haigh, S J; Gholinia, A; Mishchenko, A; Lozada, M; Georgiou, T; Woods, C R; Withers, F; Blake, P; Eda, G; Wirsig, A; Hucho, C; Watanabe, K; Taniguchi, T; Geim, A K; Gorbachev, R V Electronic Properties of Graphene Encapsulated with Different Two-Dimensional Atomic Crystals Journal Article NANO LETTERS, 14 (6), pp. 3270-3276, 2014, ISSN: 1530-6984. @article{ISI:000337337100045, title = {Electronic Properties of Graphene Encapsulated with Different Two-Dimensional Atomic Crystals}, author = {A V Kretinin and Y Cao and J S Tu and G L Yu and R Jalil and K S Novoselov and S J Haigh and A Gholinia and A Mishchenko and M Lozada and T Georgiou and C R Woods and F Withers and P Blake and G Eda and A Wirsig and C Hucho and K Watanabe and T Taniguchi and A K Geim and R V Gorbachev}, doi = {10.1021/nl5006542}, times_cited = {0}, issn = {1530-6984}, year = {2014}, date = {2014-06-01}, journal = {NANO LETTERS}, volume = {14}, number = {6}, pages = {3270-3276}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micrometer-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulfides and hBN are found to exhibit consistently high carrier mobilities of about 60 000 cm(2) V-1 s(-1). In contrast, encapsulation with atomically flat layered oxides such as mica, bismuth strontium calcium copper oxide, and vanadium pentoxide results in exceptionally low quality of graphene devices with mobilities of similar to 1000 cm(2) V-1 s(-1). We attribute the difference mainly to self-cleansing that takes place at interfaces between graphene, hBN, and transition metal dichalcogenides. Surface contamination assembles into large pockets allowing the rest of the interface to become atomically clean. The cleansing process does not occur for graphene on atomically flat oxide substrates.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micrometer-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulfides and hBN are found to exhibit consistently high carrier mobilities of about 60 000 cm(2) V-1 s(-1). In contrast, encapsulation with atomically flat layered oxides such as mica, bismuth strontium calcium copper oxide, and vanadium pentoxide results in exceptionally low quality of graphene devices with mobilities of similar to 1000 cm(2) V-1 s(-1). We attribute the difference mainly to self-cleansing that takes place at interfaces between graphene, hBN, and transition metal dichalcogenides. Surface contamination assembles into large pockets allowing the rest of the interface to become atomically clean. The cleansing process does not occur for graphene on atomically flat oxide substrates. |
2013 |
Britnell, L; Ribeiro, R M; Eckmann, A; Jalil, R; Belle, B D; Mishchenko, A; Kim, Y -J; Gorbachev, R V; Georgiou, T; Morozov, S V; Grigorenko, A N; Geim, A K; Casiraghi, C; Neto, Castro A H; Novoselov, K S Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films Journal Article 2081 SCIENCE, 340 (6138), pp. 1311-1314, 2013, ISSN: 0036-8075. @article{ISI:000320320200039, title = {Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films}, author = {L Britnell and R M Ribeiro and A Eckmann and R Jalil and B D Belle and A Mishchenko and Y -J Kim and R V Gorbachev and T Georgiou and S V Morozov and A N Grigorenko and A K Geim and C Casiraghi and Castro A H Neto and K S Novoselov}, doi = {10.1126/science.1235547}, times_cited = {2081}, issn = {0036-8075}, year = {2013}, date = {2013-06-14}, journal = {SCIENCE}, volume = {340}, number = {6138}, pages = {1311-1314}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, address = {1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA}, abstract = {The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D crystals. Such a concept has already proven fruitful for a number of electronic applications in the area of ultrathin and flexible devices. Here, we expand the range of such structures to photoactive ones by using semiconducting transition metal dichalcogenides (TMDCs)/graphene stacks. Van Hove singularities in the electronic density of states of TMDC guarantees enhanced light-matter interactions, leading to enhanced photon absorption and electron-hole creation (which are collected in transparent graphene electrodes). This allows development of extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 ampere per watt (corresponding to an external quantum efficiency of above 30%).}, keywords = {}, pubstate = {published}, tppubtype = {article} } The isolation of various two-dimensional (2D) materials, and the possibility to combine them in vertical stacks, has created a new paradigm in materials science: heterostructures based on 2D crystals. Such a concept has already proven fruitful for a number of electronic applications in the area of ultrathin and flexible devices. Here, we expand the range of such structures to photoactive ones by using semiconducting transition metal dichalcogenides (TMDCs)/graphene stacks. Van Hove singularities in the electronic density of states of TMDC guarantees enhanced light-matter interactions, leading to enhanced photon absorption and electron-hole creation (which are collected in transparent graphene electrodes). This allows development of extremely efficient flexible photovoltaic devices with photoresponsivity above 0.1 ampere per watt (corresponding to an external quantum efficiency of above 30%). |
Nair, R R; Tsai, I-L; Sepioni, M; Lehtinen, O; Keinonen, J; Krasheninnikov, A V; Neto, Castro A H; Katsnelson, M I; Geim, A K; Grigorieva, I V Dual origin of defect magnetism in graphene and its reversible switching by molecular doping Journal Article NATURE COMMUNICATIONS, 4 , 2013, ISSN: 2041-1723. @article{ISI:000323625200007, title = {Dual origin of defect magnetism in graphene and its reversible switching by molecular doping}, author = {R R Nair and I-L Tsai and M Sepioni and O Lehtinen and J Keinonen and A V Krasheninnikov and Castro A H Neto and M I Katsnelson and A K Geim and I V Grigorieva}, doi = {10.1038/ncomms3010}, times_cited = {0}, issn = {2041-1723}, year = {2013}, date = {2013-06-01}, journal = {NATURE COMMUNICATIONS}, volume = {4}, publisher = {NATURE PUBLISHING GROUP}, address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND}, abstract = {Control of magnetism by applied voltage is desirable for spintronics applications. Finding a suitable material remains an elusive goal, with only a few candidates found so far. Graphene is one of them and attracts interest because of its weak spin-orbit interaction, the ability to control electronic properties by the electric field effect and the possibility to introduce paramagnetic centres such as vacancies and adatoms. Here we show that the magnetism of adatoms in graphene is itinerant and can be controlled by doping, so that magnetic moments are switched on and off. The much-discussed vacancy magnetism is found to have a dual origin, with two approximately equal contributions; one from itinerant magnetism and the other from dangling bonds. Our work suggests that graphene's spin transport can be controlled by the field effect, similar to its electronic and optical properties, and that spin diffusion can be significantly enhanced above a certain carrier density.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Control of magnetism by applied voltage is desirable for spintronics applications. Finding a suitable material remains an elusive goal, with only a few candidates found so far. Graphene is one of them and attracts interest because of its weak spin-orbit interaction, the ability to control electronic properties by the electric field effect and the possibility to introduce paramagnetic centres such as vacancies and adatoms. Here we show that the magnetism of adatoms in graphene is itinerant and can be controlled by doping, so that magnetic moments are switched on and off. The much-discussed vacancy magnetism is found to have a dual origin, with two approximately equal contributions; one from itinerant magnetism and the other from dangling bonds. Our work suggests that graphene's spin transport can be controlled by the field effect, similar to its electronic and optical properties, and that spin diffusion can be significantly enhanced above a certain carrier density. |
Ponomarenko, L A; Belle, B D; Jalil, R; Britnell, L; Gorbachev, R V; Geim, A K; Novoselov, K S; Neto, Castro A H; Eaves, L; Katsnelson, M I Field-effect control of tunneling barrier height by exploiting graphene's low density of states Journal Article JOURNAL OF APPLIED PHYSICS, 113 (13), 2013, ISSN: 0021-8979. @article{ISI:000317238000069, title = {Field-effect control of tunneling barrier height by exploiting graphene's low density of states}, author = {L A Ponomarenko and B D Belle and R Jalil and L Britnell and R V Gorbachev and A K Geim and K S Novoselov and Castro A H Neto and L Eaves and M I Katsnelson}, doi = {10.1063/1.4795542}, times_cited = {0}, issn = {0021-8979}, year = {2013}, date = {2013-04-07}, journal = {JOURNAL OF APPLIED PHYSICS}, volume = {113}, number = {13}, publisher = {AMER INST PHYSICS}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {We exploit the low density of electronic states of graphene to modulate the tunnel current flowing perpendicular to the atomic layers of a multi-layer graphene-boron nitride device. This is achieved by using the electric field effect to raise the Fermi energy of the graphene emitter layer and thereby reduce the effective barrier height for tunneling electrons. We discuss how the electron charge density in the graphene layers and the properties of the boron nitride tunnel barrier determine the device characteristics under operating conditions and derive expressions for carrier tunneling in these highly anisotropic layered heterostructures. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795542]}, keywords = {}, pubstate = {published}, tppubtype = {article} } We exploit the low density of electronic states of graphene to modulate the tunnel current flowing perpendicular to the atomic layers of a multi-layer graphene-boron nitride device. This is achieved by using the electric field effect to raise the Fermi energy of the graphene emitter layer and thereby reduce the effective barrier height for tunneling electrons. We discuss how the electron charge density in the graphene layers and the properties of the boron nitride tunnel barrier determine the device characteristics under operating conditions and derive expressions for carrier tunneling in these highly anisotropic layered heterostructures. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795542] |
2012 |
Britnell, L; Gorbachev, R V; Jalil, R; Belle, B D; Schedin, F; Mishchenko, A; Georgiou, T; Katsnelson, M I; Eaves, L; Morozov, S V; Peres, N M R; Leist, J; Geim, A K; Novoselov, K S; Ponomarenko, L A Field-Effect Tunneling Transistor Based on Vertical Graphene Heterostructures Journal Article SCIENCE, 335 (6071), pp. 947-950, 2012, ISSN: 0036-8075. @article{ISI:000300931800040, title = {Field-Effect Tunneling Transistor Based on Vertical Graphene Heterostructures}, author = {L Britnell and R V Gorbachev and R Jalil and B D Belle and F Schedin and A Mishchenko and T Georgiou and M I Katsnelson and L Eaves and S V Morozov and N M R Peres and J Leist and A K Geim and K S Novoselov and L A Ponomarenko}, doi = {10.1126/science.1218461}, times_cited = {0}, issn = {0036-8075}, year = {2012}, date = {2012-02-24}, journal = {SCIENCE}, volume = {335}, number = {6071}, pages = {947-950}, publisher = {AMER ASSOC ADVANCEMENT SCIENCE}, address = {1200 NEW YORK AVE, NW, WASHINGTON, DC 20005 USA}, abstract = {An obstacle to the use of graphene as an alternative to silicon electronics has been the absence of an energy gap between its conduction and valence bands, which makes it difficult to achieve low power dissipation in the OFF state. We report a bipolar field-effect transistor that exploits the low density of states in graphene and its one-atomic-layer thickness. Our prototype devices are graphene heterostructures with atomically thin boron nitride or molybdenum disulfide acting as a vertical transport barrier. They exhibit room-temperature switching ratios of approximate to 50 and approximate to 10,000, respectively. Such devices have potential for high-frequency operation and large-scale integration.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An obstacle to the use of graphene as an alternative to silicon electronics has been the absence of an energy gap between its conduction and valence bands, which makes it difficult to achieve low power dissipation in the OFF state. We report a bipolar field-effect transistor that exploits the low density of states in graphene and its one-atomic-layer thickness. Our prototype devices are graphene heterostructures with atomically thin boron nitride or molybdenum disulfide acting as a vertical transport barrier. They exhibit room-temperature switching ratios of approximate to 50 and approximate to 10,000, respectively. Such devices have potential for high-frequency operation and large-scale integration. |