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

DIPC Seminars

Jeffrey Kelber. Department of Chemistry, University of North Texas, Denton, USA
Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4, Donostia
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Direct Growth of 2D Materials on Practical Substrates: From Surface Chemistry to New Physics and Devices 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).