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@INPROCEEDINGS{Pecz:827190,
      author       = {Pecz, Bela and Kovacs, Andras and Dunin-Borkowski, Rafal
                      and Yakimova, Rositza and Heuken, Michael},
      title        = {{N}itride layers grown on patterned graphene/{S}i{C}},
      address      = {Weinheim, Germany},
      publisher    = {Wiley-VCH Verlag GmbH $\&$ Co. KGaA},
      reportid     = {FZJ-2017-01388},
      pages        = {630 - 631},
      year         = {2016},
      comment      = {European Microscopy Congress 2016: Proceedings},
      booktitle     = {European Microscopy Congress 2016:
                       Proceedings},
      abstract     = {Self-heating of high power GaN devices during their
                      operation is a major drawback that limits the performance.
                      Integration of sheets with very high thermal conductivity
                      material could help in this matter. After some unsuccessful
                      GaN growth experiments carried out directly on graphene, we
                      succeeded to grow nitride layers on patterned
                      graphene/6H-SiC by Metalorganic Chemical Vapour Deposition
                      (MOCVD). The growth is similar to the well-known Epitaxial
                      Lateral Overgrowth method in which the graphene buried
                      stripes are overgrown laterally from the window regions,
                      where AlN could grow on bare SiC with epitaxy. An AlN buffer
                      layer was first deposited on patterned graphene/6H-SiC
                      surface followed by a deposition of ~ 300 nm thick
                      Al0.2Ga0.8N and ~ 1.5 µm thick GaN layer. The AlN buffer
                      deposited onto the graphene stripe was grown in a 3D way
                      (Fig.1a). The heterostructure was studied using
                      aberration-corrected transmission electron microscopy (TEM)
                      methods in combination of electron energy-loss X-ray
                      spectroscopy (EDXS) and electron energy-loss spectroscopy
                      (EELS). TEM specimens were prepared using both conventional
                      and focused ion beam methods.The most surprising details of
                      this study is the appearance of the AlN/GaN superlattices,
                      which were formed in a self-organised way over the buffer
                      layer. Instead the ternary AlGaN we have superlattice (Fig.
                      1.b and c) in which the thickness of the AlN/GaN is
                      determined by the available elements from the Al0.2Ga0.8N
                      which we wanted to grow. The control sample (without
                      graphene) showed a much more flat AlN buffer and a ternary
                      Al0.2Ga0.8N on that without any phase separation. EDXS
                      mapping and also superlattice reflections show however,
                      clearly the complete phase separation in the case the
                      nitride layers are grown on graphene. We suppose, that some
                      excess carbon induced the phase separation.The detailed TEM
                      studies revealed the AlN nucleation directly on SiC and
                      lateral overgrowth of graphene island as shown in Fig.2a.
                      The high resolution image in Fig.2.b shows three layers of
                      graphene and the AlN that is in epitaxy with SiC. Both
                      interfaces are sharp and no interdiffusion of the elements
                      are observed according to the Si, C (not shown) and Al maps
                      in Fig. 2c The results show that high quality GaN layer over
                      graphene/SiC can be grown with MOCVD that can serve as
                      templates for high power GaN devices.},
      month         = {Aug},
      date          = {2016-08-28},
      organization  = {16th European Microscopy Congress (EMC
                       2016), Lyon (France), 28 Aug 2016 - 2
                       Sep 2016},
      cin          = {PGI-5 / ER-C-1},
      cid          = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)ER-C-1-20170209},
      pnm          = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)8 / PUB:(DE-HGF)7},
      doi          = {10.1002/9783527808465.EMC2016.6338},
      url          = {https://juser.fz-juelich.de/record/827190},
}