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G L Yu,
R Jalil,
Branson Belle,
Alexander S Mayorov,
Peter Blake,
Frederick Schedin, Sergey V Morozov,
Leonid A Ponomarenko,
F Chiappini,
S Wiedmann,
Uli Zeitler,
Mikhail I Katsnelson,
A K Geim,
Kostya S Novoselov,
Daniel C Elias
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ABSTRACT: Capacitance measurements provide a powerful means of probing the density of states. The technique has proved particularly successful in studying 2D electron systems, revealing a number of interesting many-body effects. Here, we use large-area high-quality graphene capacitors to study behavior of the density of states in this material in zero and high magnetic fields. Clear renormalization of the linear spectrum due to electron-electron interactions is observed in zero field. Quantizing fields lead to splitting of the spin- and valley-degenerate Landau levels into quartets separated by interaction-enhanced energy gaps. These many-body states exhibit negative compressibility but the compressibility returns to positive in ultrahigh B. The reentrant behavior is attributed to a competition between field-enhanced interactions and nascent fractional states.
Proceedings of the National Academy of Sciences 02/2013; 110(9):3282-6. · 9.68 Impact Factor
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Thanasis Georgiou,
Rashid Jalil,
Branson D Belle,
Liam Britnell,
Roman V Gorbachev, Sergey V Morozov,
Yong-Jin Kim,
Ali Gholinia,
Sarah J Haigh,
Oleg Makarovsky,
Laurence Eaves,
Leonid A Ponomarenko,
Andre K Geim,
Kostya S Novoselov,
Artem Mishchenko
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ABSTRACT: The celebrated electronic properties of graphene have opened the way for materials just one atom thick to be used in the post-silicon electronic era. An important milestone was the creation of heterostructures based on graphene and other two-dimensional crystals, which can be assembled into three-dimensional stacks with atomic layer precision. Such layered structures have already demonstrated a range of fascinating physical phenomena, and have also been used in demonstrating a prototype field-effect tunnelling transistor, which is regarded to be a candidate for post-CMOS (complementary metal-oxide semiconductor) technology. The range of possible materials that could be incorporated into such stacks is very large. Indeed, there are many other materials with layers linked by weak van der Waals forces that can be exfoliated and combined together to create novel highly tailored heterostructures. Here, we describe a new generation of field-effect vertical tunnelling transistors where two-dimensional tungsten disulphide serves as an atomically thin barrier between two layers of either mechanically exfoliated or chemical vapour deposition-grown graphene. The combination of tunnelling (under the barrier) and thermionic (over the barrier) transport allows for unprecedented current modulation exceeding 1 × 10(6) at room temperature and very high ON current. These devices can also operate on transparent and flexible substrates.
Nature Nanotechnology 12/2012; · 27.27 Impact Factor
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Thanasis Georgiou,
Rashid Jalil,
Branson D. Belle,
Liam Britnell,
Roman V. Gorbachev, Sergey V. Morozov,
Yong-Jin Kim,
Ali Gholinia,
Sarah J. Haigh,
Oleg Makarovsky,
Laurence Eaves,
Leonid A. Ponomarenko,
Andre K. Geim,
Kostya S. Novoselov,
Artem Mishchenko
[show abstract]
[hide abstract]
ABSTRACT: The celebrated electronic properties of graphene have opened way for
materials just one-atom-thick to be used in the post-silicon electronic era. An
important milestone was the creation of heterostructures based on graphene and
other two-dimensional (2D) crystals, which can be assembled in 3D stacks with
atomic layer precision. These layered structures have already led to a range of
fascinating physical phenomena, and also have been used in demonstrating a
prototype field effect tunnelling transistor - a candidate for post-CMOS
technology. The range of possible materials which could be incorporated into
such stacks is very large. Indeed, there are many other materials where layers
are linked by weak van der Waals forces, which can be exfoliated and combined
together to create novel highly-tailored heterostructures. Here we describe a
new generation of field effect vertical tunnelling transistors where 2D
tungsten disulphide serves as an atomically thin barrier between two layers of
either mechanically exfoliated or CVD-grown graphene. Our devices have
unprecedented current modulation exceeding one million at room temperature and
can also operate on transparent and flexible substrates.
11/2012;
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ABSTRACT: The above question is frequently asked by theorists who are interested in graphene as a model system, especially in context of relativistic quantum physics. We offer an experimental answer by describing electron transport in suspended devices with carrier mobilities of several 10(6) cm(2) V(-1) s(-1) and with the onset of Landau quantization occurring in fields below 5 mT. The observed charge inhomogeneity is as low as ≈10(8) cm(-2), allowing a neutral state with a few charge carriers per entire micrometer-scale device. Above liquid helium temperatures, the electronic properties of such devices are intrinsic, being governed by thermal excitations only. This yields that the Dirac point can be approached within 1 meV, a limit currently set by the remaining charge inhomogeneity. No sign of an insulating state is observed down to 1 K, which establishes the upper limit on a possible bandgap.
Nano Letters 08/2012; 12(9):4629-34. · 13.20 Impact Factor
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Liam Britnell,
Roman V Gorbachev,
Rashid Jalil,
Branson D Belle,
Fred Schedin,
Mikhail I Katsnelson,
Laurence Eaves, Sergey V Morozov,
Alexander S Mayorov,
Nuno M R Peres,
Antonio H Castro Neto,
Jon Leist,
Andre K Geim,
Leonid A Ponomarenko,
Kostya S Novoselov
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ABSTRACT: We investigate the electronic properties of ultrathin hexagonal boron nitride (h-BN) crystalline layers with different conducting materials (graphite, graphene, and gold) on either side of the barrier layer. The tunnel current depends exponentially on the number of h-BN atomic layers, down to a monolayer thickness. Conductive atomic force microscopy scans across h-BN terraces of different thickness reveal a high level of uniformity in the tunnel current. Our results demonstrate that atomically thin h-BN acts as a defect-free dielectric with a high breakdown field. It offers great potential for applications in tunnel devices and in field-effect transistors with a high carrier density in the conducting channel.
Nano Letters 03/2012; 12(3):1707-10. · 13.20 Impact Factor
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Liam Britnell,
Roman V. Gorbachev,
Rashid Jalil,
Branson D. Belle,
Fred Schedin,
Mikhail I. Katsnelson,
Laurence Eaves, Sergey V. Morozov,
Alexander S. Mayorov,
Nuno M. R. Peres,
Antonio H. Castro Neto,
Jon Leist,
Andre K. Geim,
Leonid A. Ponomarenko,
Kostya S. Novoselov
[show abstract]
[hide abstract]
ABSTRACT: We investigate the electronic properties of heterostructures based on
ultrathin hexagonal boron nitride (h-BN) crystalline layers sandwiched between
two layers of graphene as well as other conducting materials (graphite, gold).
The tunnel conductance depends exponentially on the number of h-BN atomic
layers, down to a monolayer thickness. Exponential behaviour of I-V
characteristics for graphene/BN/graphene and graphite/BN/graphite devices is
determined mainly by the changes in the density of states with bias voltage in
the electrodes. Conductive atomic force microscopy scans across h-BN terraces
of different thickness reveal a high level of uniformity in the tunnel current.
Our results demonstrate that atomically thin h-BN acts as a defect-free
dielectric with a high breakdown field; it offers great potential for
applications in tunnel devices and in field-effect transistors with a high
carrier density in the conducting channel.
02/2012;
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ABSTRACT: We report large-yield production of graphene flakes on glass by anodic bonding. Under optimum conditions, we counted several tens of flakes with lateral size around 20-30 μm and a few tens of flakes with larger size. About 60-70% of the flakes have a negligible D peak. We show that it is possible to easily transfer the flakes by the wedging technique. The transfer on silicon does not damage graphene and lowers the doping. The charge mobility of the transferred flakes on silicon is on the order of 6000 cm(2)/V s (at a carrier concentration of 10(12) cm(-2)), which is typical for devices prepared on this substrate with exfoliated graphene.
ACS Nano 09/2011; 5(10):7700-6. · 10.77 Impact Factor
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Alexander S Mayorov,
Roman V Gorbachev, Sergey V Morozov,
Liam Britnell,
Rashid Jalil,
Leonid A Ponomarenko,
Peter Blake,
Kostya S Novoselov,
Kenji Watanabe,
Takashi Taniguchi,
A K Geim
[show abstract]
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ABSTRACT: Devices made from graphene encapsulated in hexagonal boron-nitride exhibit pronounced negative bend resistance and an anomalous Hall effect, which are a direct consequence of room-temperature ballistic transport at a micrometer scale for a wide range of carrier concentrations. The encapsulation makes graphene practically insusceptible to the ambient atmosphere and, simultaneously, allows the use of boron nitride as an ultrathin top gate dielectric.
Nano Letters 06/2011; 11(6):2396-9. · 13.20 Impact Factor
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Small 07/2010; 6(14):1469-73. · 8.35 Impact Factor
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Peter Blake,
Paul D Brimicombe,
Rahul R Nair,
Tim J Booth,
Da Jiang,
Fred Schedin,
Leonid A Ponomarenko, Sergey V Morozov,
Helen F Gleeson,
Ernie W Hill,
Andre K Geim,
Kostya S Novoselov
[show abstract]
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ABSTRACT: Graphene is only one atom thick, optically transparent, chemically inert, and an excellent conductor. These properties seem to make this material an excellent candidate for applications in various photonic devices that require conducting but transparent thin films. In this letter, we demonstrate liquid crystal devices with electrodes made of graphene that show excellent performance with a high contrast ratio. We also discuss the advantages of graphene compared to conventionally used metal oxides in terms of low resistivity, high transparency and chemical stability.
Nano Letters 07/2008; 8(6):1704-8. · 13.20 Impact Factor
