Speaker: Stephan Roche
Affiliation: ICN2 - Catalan Institute of Nanoscience Nanotechnology
Abstract Details: In this talk, I will discuss charge and spin transport in complex forms of graphene (chemically reduced, polycrystalline graphene, chemically functionalized) of relevance for current and future applications in flexible electronics, energy harvesting and spintronics. The crucial contribution of multiscale simulation will be illustrated, demonstrating an achieved high level of predictive capability for very large system sizes (with up to 1 billion atoms), reaching the experimental and technology scales. One illustration will be the quantitative analysis on the transport properties of structural imperfections produced during the wafer-scale production of graphene through chemical growth (CVD), or the mechanical/chemical exfoliation and chemical transfer to versatile substrates, followed by the device fabrication. Fundamental properties of charge mobilities in polycrystalline graphene, accounting the variability in average grain sizes and chemical reactivity of grain boundaries as observed in real samples grown by CVD will be presented, together with their relevance for device optimization and diversification of applied functionalities such as chemical sensing. In a second part, I will focus on spin transport in graphene functionalized by adatom deposits (gold, thallium). Unique spin dynamics phenomena in graphene, such as the formation of the Quantum Spin Hall state and a crossover to the Spin Hall effect under adatom segregation will be shown, as well as the role of spin-pseudospin entanglement in driving the spin relaxation mechanism in the ultraclean graphene limit. These results could open unprecedented perspectives for achieving proofs of concepts of spin manipulation, contributing to the progress towards non-charge based revolutionary information processing and computing. [1] L. E. F. Foa Torres, S. Roche, and J. C. Charlier, Introduction to Graphene- Based Nanomaterials: From Electronic Structure to Quantum Transport (Cambridge University Press, Cambridge, 2014). [2] D. Van Tuan, J. Kotakoski, T. Louvet, F. Ortmann, J. C. Meyer, S. Roche, Nano Lett. 13, 1730−1735 (2013); A.W. Cummings, D. Duong, V. Luan Nguyen, D. Van Tuan, J. Kotakoski , J.E. Barrios Vargas, Y. Hee Lee, S. Roche; Advanced Materials 26, Issue 30, 5079-5094 (2014). [3] Dinh Van Tuan, F. Ortmann, D. Soriano, S. O. Valenzuela, S. Roche, Nature Physics, 10, 857–863 (2014) [4] A. Cresti, D. Van Tuan, D. Soriano, A. W. Cummings, S. Roche, Phys. Rev. Lett (in press), arXiv:1411.5837"Click HERE for directions

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