Bilayer graphene

From Wikipedia, the free encyclopedia
Jump to: navigation, search

Bilayer graphene (BLG[citation needed]) is a material consisting of two layers of graphene. It is very difficult to grow only bilayer graphene without monolayer graphene.

Quantum Hall Effect[edit]

Like a single layer of graphene, bilayer graphene has been shown to exhibit the quantum Hall effect.

Excitonic Condensation[edit]

Bilayer graphene is being studied for its potential to realize a Bose–Einstein condensate of excitons.[1] Electrons and holes are fermions, but when they form an exciton, they become bosons, allowing Bose-Einstein condensation to occur. Exciton condensates in bilayer systems have been shown theoretically to carry a large current.[2]

Bilayer Graphene FETs[edit]

Bilayer graphene can be used to construct field effect transistors.[3]

Porous Nanoflakes[edit]

Hybridization processes change the intrinsic properties of graphene and/or induce poor interfaces. In 2014 a general route to obtain unstacked graphene via facile, templated, catalytic growth was announced. The resulting material offers specific surface area of 1628 m2 g-1, electrical conductivity and mesoporous structure.[4]

The material is made with a mesoporous nanoflake template. Graphene layers are deposited onto the template. The carbon atoms accumulate in the mesopores, forming protuberances that act as spacers to prevent stacking. Protuberance density is approximately 5.8×1014 m−2. Graphene is deposited on both sides of the flakes.[4]

During CVD synthesis the protuberances produce intrinsically unstacked double-layer graphene after the removal of the nanoflakes. The presence of such protuberances on the surface can weaken the π-π interactions between graphene layers and thus reduce stacking. The bilayer graphene shows a specific surface area of 1628 m2/g, a pore size ranging from 2 to 7 nm and a total pore volume of 2.0 cm3/g.[4]

Using bilary graphene as cathode material for a lithium sulfur battery yielded reversible capacities of 1034 and 734 mA h/g at discharge rates of 5 and 10 C, respectively. After 1000 cycles reversible capacities of some 530 and 380 mA h/g were retained at 5 and 10 C, with coulombic efficiency constants at 96 and 98 %, respectively.[4]

Electrical conductivity of 438 S/cm was obtained. Even after the infiltration of sulfur, electrical conductivity of 107 S cm/1 was retained. The graphene’s unique porous structure allowed the effective storage of sulfur in the interlayer space, which gives rise to an efficient connection between the sulfur and graphene and prevents the diffusion of polysulfides into the electrolyte.[4]

References[edit]

  1. ^ Barlas, Y.; Côté, R.; Lambert, J.; MacDonald, A. H. (2010). "Anomalous Exciton Condensation in Graphene Bilayers". Physical Review Letters 104 (9). arXiv:0909.1502. Bibcode:2010PhRvL.104i6802B. doi:10.1103/PhysRevLett.104.096802.  edit
  2. ^ Su, J. J.; MacDonald, A. H. (2008). "How to make a bilayer exciton condensate flow". Nature Physics 4 (10): 799–802. arXiv:0801.3694. Bibcode:2008NatPh...4..799S. doi:10.1038/nphys1055.  edit
  3. ^ Schwierz, F. (2010). "Graphene transistors". Nature Nanotechnology 5 (7): 487–496. doi:10.1038/nnano.2010.89. PMID 20512128.  edit
  4. ^ a b c d e Tue, 03/04/2014 - 3:35pm. "Researchers develop intrinsically unstacked double-layer graphene". Rdmag.com. doi:10.1038/ncomms4410. Retrieved 2014-04-05.