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Growth mechanisms and electronic properties of epitaxial graphene

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Epitaxial growth on SiC is a candidate for exploiting graphene’s extraordinary properties in technological applications [1]. Growth is achieved by annealing at temperatures above 1200 ◦C, causing Si to evaporate from the SiC preferentially to C; the resulting carbon-rich surface forms a graphitic layer with the structural and electronic properties extremely sensitive to annealing conditions [2].

We present electronic transport and low energy electron microscopy (LEEM) data for (000-1) 4H SiC samples annealed under UHV at various temperatures. The evolution of coherent electronic transport occurs for samples annealed at higher temperatures, as the size of individual graphene domains increases from tens of nm to several microns. Using a two-stage annealing protocol, we show that the larger grain size is due to a coalescence mechanism, as opposed to faster propagation of single grains.

Fitting Magnetotransport (MR) data to weak localisation or weak anti-localisation models [3, 4] yields electron scattering rates for various processes, while subtraction of the fits from the measured data allows less dominant contributions to magnetotransport from electron-electron interations and mesoscopic phenomena to be discerned.

This work was supported by the EPSRC and Intel Ireland.

References 1. [1] C. Berger, Z. Song, T. Li, X. Li, A.Y. Ogbazghi, R. Feng, Z. Dai, A.N. Marchenkov, E.H. Conrad, P.N. First, and W.A. deHeer. Ultrathin epitaxial graphite: 2D elec- tron gas properties and a route toward graphene-based nanoelectronics. Journal of Physical Chemistry B, 108(52):19912–19916, 2004. 2. [2] Luxmi, N. Srivastava, Guowei He, R. M. Feenstra, and P. J. Fisher. Comparison of graphene formation on C-face and Si-face SiC {0001} surfaces. Phys. Rev. B, 82(23):235406, Dec 2010. 3. [3] Xiaosong Wu, Xuebin Li, Zhimin Song, Claire Berger, and Walt A. de Heer. Weak antilocalization in epitaxial graphene: Evidence for chiral electrons. Phys. Rev. Lett., 98(13):136801, 2007. 4. [4] E. McCann, K. Kechedzhi, Vladimir I. Fal’ko, H. Suzuura, T. Ando, and B. L. Altshuler. Weak-localization magnetoresistance and valley symmetry in graphene. Phys. Rev. Lett., 97(14):146805, 2006.

This talk is part of the Semiconductor Physics Group Seminars series.

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