"Direct Growth of 2D Materials on Practical Substrates: From Surface Chemistry to New Physics and Devices"

Who: Jeffrey Kelber. Department of Chemistry, University of North Texas, Denton, USA

Place: Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4, Donostia

Date: Thursday, 15 January 2015, 12:00

The industrial scale development of devices based on 2D materials requires some original
thinking in their deposition and growth. For graphene, this means direct growth of single or few
layer graphene, without physical transfer or metal catalysts, on appropriate dielectric substrates.
For hexagonal BN, this means the growth of epitaxial few layer films, with atomically precise
control of layer thickness?difficult to achieve via the usual route of borazine pyrolysis. We
have recently demonstrated the direct, layer-by-layer growth of high quality azimuthally oriented
graphene on Co3O4(111)/Co(0001) by molecular beam epitaxy (MBE) [1], and the layer-by-layer
growth of BN(0001) on Co(0001) by atomic layer deposition [2]. Both the graphene/oxide and
BN/Co systems have the potential for novel spin transport behavior and device applications.
For graphene/Co3O4(0001)/Co(0001), strong graphene-to-oxide charge transfer leads to
coupling between localized oxide spins and delocalized graphene carriers, yielding substrateinduced
polarization of graphene carriers, and antiferromagnetic hysteresis to > 400 K [3], even
though TN for Co3O4 is only 40 K. Very recent experimental and theoretical developments
suggest that such graphene growth can be extended to other p-type magnetic oxides, making
possible a broad array of robust devices based on coherent spin polarization and transport,
rather than inefficient injection of discrete spins. For BN, recent theoretical work [4] suggests
highly efficient spin filtering for Co/BN/Co magnetic tunnel junctions, yielding tunneling
magnetoresistance values > 1000%, but highly dependent on the number of BN layers. This
talk will focus on the surface chemistry of both graphene and BN deposition, and how this
chemistry in both cases yields exciting new electronic and magnetic properties.
Acknowledgements: This work was partially supported by the Semiconductor Research
Corporation.

[1] M. Zhou, F.L. Pasquale, P.A. Dowben, A. Boosalis, M. Schubert, V. Darakchieva, R.
Yakimova, J.A. Kelber. Direct graphene growth on Co3O4(111) by molecular beam epitaxy. J
Phys Cond Matt. 24 (2012) 072201.
[2] J. Beatty, Y. Cao, I. Tanabe, M. Driver, P.A. Dowben, J.A. Kelber. Atomic layer-by-layer
deposition of h-BN(0001) on cobalt: A building block for spintronics and graphene electronics.
Mater Res Express. Submitted for publication (2014).
[3] Y. Wang, L. Kong, F.L. Pasquale, Y. Cao, B. Dong, I. Tanabe, C. Binek, P.A. Dowben, J.A.
Kelber. Graphene mediated domain formation in exchange coupled
graphene/Co3O4(111)/Co(0001) trilayers. J Phys : Cond Matt. 25 (2013) 472203.
[4] S. Faleev, O.N. Mryasov, S. Parkin. Brillouin zone filtering mechanism of enhanced TMR and
correlation effects in Co(0001)/h-BN/Co(0001) magnetic tunnel junctions. Phys Rev Lett. In
press (2014).

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