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SUMMARY:Scanning gate microscopy: local mapping of functionality of graphe
 ne devices - Vishal Panchal\, National Physical Laboratory
DTSTART:20130429T131500Z
DTEND:20130429T141500Z
UID:TALK45090@talks.cam.ac.uk
CONTACT:Dr Malcolm Connolly
DESCRIPTION:Graphene is a two-dimensional material comprised of only carbo
 n atoms closely packed in a honeycomb crystal structure. Devices fabricate
 d out of epitaxial graphene grown on SiC have shown great promise for comm
 ercialization [1\,2]. However\, due to the complicated growth procedure\, 
 even the best epitaxial samples contain ~95% mono-layer (1LG) and ~5% bi-l
 ayer (2LG) graphene coverage [3]. Such samples have been shown to exhibit 
 a work function difference of ~110±21 meV between 1LG and 2LG [4]\, which
  can affect the transport properties of graphene devices.\nWe apply scanni
 ng gate microscopy with conductive (and magnetic) probes to studies of the
  local properties of graphene devices. We investigate the transverse volta
 ge (Vxy) response of the sensor to a non-uniform magnetic field produced b
 y a magnetic probe. Using this technique\, we are able determine the stray
  field of a few types of commercial probes and optimize the magnetic respo
 nse of the graphene Hall sensor [5]. We demonstrate that graphene Hall sen
 sors can be successfully used to measure small magnetic fields and moments
 .\nWe also study the electronic properties of 1LG and 2LG by measuring the
  longitudinal voltage (Vxx) and Vxy response to an electric field produced
  by a local scanning gate. The Vxx and Vxy mapping indicates that isolated
  2LG islands provide an effect of screening the local electric field\, and
  can affect transport measurements. The screening efficiency will depend o
 n geometry of 2LG domains and their exact position with respect to the lea
 ds. These measurements allow investigating the possible effect of decoupli
 ng between individual layers of graphene.\n\n[1] C. Dimitrakopoulos et al.
 \, 28 (5)\, 985 (2010).\n[2] Y.-M. Lin et al.\, Science 327\, 662 (2010).\
 n[3] V. Panchal et al.\, 12th IEEE Conf. on Nanotechnology (2012).\n[4] O.
  Kazakova et al.\, Crystals 3 (1)\, 191-233 (2013).\n[5] V. Panchal et al.
 \, IEEE Trans. Magn. 49 (7)\, in press (2013).
LOCATION:Mott Seminar Room
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