Formation of hexagonal boron nitride on graphene-covered copper surfaces
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Shonali Dhingra Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
Jun Li Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
Kehao Zhang, Nicholas A. Simonson, and Joshua A. Robinson Department of Materials Science and Engineering and Center for Two-Dimensional and Layered Materials, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
Ning Lu, Qingxiao Wang, and Moon J. Kim Department of Materials Science and Engineering, The University of Texas at Dallas, Richardson, Texas 75080, USA
Brian D’Urso Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
Randall M. Feenstraa) Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA (Received 11 September 2015; accepted 18 February 2016)
Graphene-covered copper surfaces have been exposed to borazine, (BH)3(NH)3, with the resulting surfaces characterized by low-energy electron microscopy. Although the intent of the experiment was to form hexagonal boron nitride (h-BN) on top of the graphene, such layers were not obtained. Rather, in isolated surface areas, h-BN is found to form lm-size islands that substitute for the graphene. Additionally, over nearly the entire surface, the properties of the layer that was originally graphene is observed to change in a manner that is consistent with the formation of a mixed h-BN/graphene alloy, i.e., h-BNC alloy. Furthermore, following the deposition of the borazine, a small fraction of the surface is found to consist of bare copper, indicating etching of the overlying graphene. The inability to form h-BN layers on top of graphene is discussed in terms of the catalytic behavior of the underlying copper surface and the decomposition of the borazine on top of the graphene.
I. INTRODUCTION
A large number of growth studies have been conducted over the past decade for various two-dimensional (2D) materials including graphene and hexagonal boron nitride (h-BN), with metal substrates being often used.1–3 The presence of the metal is generally acknowledged to provide some catalytic activity for the decomposition of the precursor molecules and the subsequent formation of the graphene or h-BN films.4,5 Indeed, for single monolayer of h-BN, this growth mode was elucidated in the early works of Nagashima et al. and Auwärter et al.6–8 For application in electronic devices, thin films of 2D materials must be removed from those substrates and then transferred onto an insulating material.9,10 For Contributing Editor: Lou Jun a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.82 J. Mater. Res., Vol. 31, No. 7, Apr 14, 2016
heterostructures, containing thin layers of different materials, the number of steps needed to build up the structure can be relatively large. Possible contamination induced by the transfer process, for each transfer step, might then be deleterious to the electrical properties of the final device.11,12 For
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