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SUMMARY:Polycrystalline graphene: atomic structure and electronic transpor
 t properties
DTSTART:20121005T141500
DTSTAMP:20260415T191155Z
UID:14f2beb86a9f8867d1a6bf3d19a15f913e5fa01e48890e09b1a24794
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. O. Yazyev\, Institute of Theoretical Physics - EPFL\nThe
 re is growing evidence of the polycrystalline nature of graphene samples a
 t micrometer length scales. Grain boundaries and dislocations\, intrinsic 
 topological defects of polycrystalline materials\, inevitably affect all k
 inds of physical properties of graphene. This talk reviews our theoretical
  efforts directed towards understanding atomic structure and electronic tr
 ansport properties of polycrystalline graphene. Recent experimental works 
 on this subject are also covered in my lecture. We introduce a general app
 roach for constructing dislocations in graphene characterized by arbitrary
  Burgers vectors and grain boundaries covering the whole range of possible
  misorientation angles [1]. By using ab initio calculations we investigate
  thermodynamic properties of grain boundaries finding energetically favora
 ble large-angle symmetric configurations as well as dramatic stabilization
  of small-angle configurations via the out-of-plane deformation\, a remark
 able feature of graphene as a truly two-dimensional material. Charge-carri
 er transport across periodic grain boundaries in graphene is shown to be g
 overned primarily by a simple momentum conservation law [2]. Two distinct 
 transport behaviors are predicted - either perfect reflection or high tran
 sparency for low-energy charge carriers depending on the grain boundary st
 ructure. Beyond the momentum conservation picture we find that the transmi
 ssion of low-energy charge carriers can be dramatically suppressed in the 
 small-angle limit [3]. This counter-intuitive behavior is explained from t
 he standpoint of resonant backscattering involving electronic states local
 ized at the dislocations. Finally\, my talk will cover advances of a joint
  experiment-theory project on controlled engineering of a degenerate grain
  boundary defect exhibiting valley-filtering properties [4].\nThese result
 s demonstrate that dislocations and grain boundaries are important intrins
 ic defects in graphene\, which can be used for engineering novel functiona
 l devices.\n\nReferences:\n[1] O. V. Yazyev\, S. G. Louie\, Topological de
 fects in graphene: Dislocations and grain boundaries. Phys. Rev. B 81\, 19
 5420 (2010). PDF\n[2] O. V. Yazyev\, S. G. Louie\, Electronic transport in
  polycrystalline graphene. Nat. Mater. 9\, 806 (2010). PDF\n[3] F. Gargiul
 o\, O. V. Yazyev\, in preparation.\n[4] J.-H. Chen\, G. Aut?s\, N. Alem\, 
 F. Gargiulo\, A. Gautam\, M. Linck\, C. Kisielowski\, O. V. Yazyev\, S. G.
  Louie\, and A. Zettl\, Controlled growth of a line defect in graphene for
  gate-tunable valley filtering\, submitted.
LOCATION:PH L1 503 http://plan.epfl.ch/?lang=en&room=PH.L1.503
STATUS:CONFIRMED
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