15:00-16:00
Transport, chemical reactivity and forces at the atomic scale: A theoretical perspective.
Dr. Ruben Perez (Nanomechanics & Scanning Probe Microscopy Theory Group Departamento de Fisica Teorica de la Materia Condensada Universidad Autonoma de Madrid, E-28049 Madrid, Spain)
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In this talk, we review our work on ab initio modeling of different problems in Materials Science and Nanotechnology that involve forces and currents at the atomic scale. We focus on our theoretical approach to understand and develop new capacities for the basic tools in Nanotechnology, the Scanning Probe Microscopes (SPMs), that enable the use of currents and forces to visualize and manipulate matter at the nanoscale [1,2]. We use a suite of total-energy methods based in Density Functional Theory (DFT) --from very efficient codes based on local orbitals to more accurate implementations based on a plane-wave basis--, in order to provide a realistic description of the mechanical and electronic properties. The transport properties are calculated with a non-equilibrium Green's function formalism, that can be naturally linked with the local orbital DFT methods.
We illustrate our methodology with four different applications:
(1) Understanding the fractional conductance peaks in metallic nanocontacts broken in the presence of different molecular species [3,4].
(2) The role of tip-sample interactions in the STM operation in the near-to-contact regime, where they can induce a substantial decrease of the current when approaching semiconductor surfaces under low bias conditions [5].
(3) The characterization of the chemical reactivity and energy dissipation processes for fullerenes and other organic molecules on surfaces [6,7]
(4) The combination of force spectroscopy measurements with our large-scale first principles calculations in order to to understand and extend the FM-AFM capabilities in key areas including single-atom manipulation [8,9] and chemical identification [10].
References:
[1] R. Garcia and R. Perez, Surf. Sci. Rep. 47, 197 (2002).
[2] J.M. Blanco, F. Flores and R. Perez, Progress in Surface Science, 81 ,403-443 (2006).
[3] P. Jelinek, R. Perez, J. Ortega and F Flores, Phys. Rev. Lett. 96, 046803 (2006);
[4] P. Jelinek et al, Phys. Rev. B 77, 115447 (2008); Nanotechnology 19, 335711 (2008).
[5] P. Jelinek, M. Svec, P. Pou, R. Perez, and V. Chab, Phys. Rev. Lett. 101, 176101 (2008).
[6] G. Otero et al., Nature 464, 865-869 (2008).
[7] R. Garcia, R. Margele and R. Perez, Nature Materials 6, 405 (2007).
[8] Y. Sugimoto, P . Jelinek, P. Pou, M. Abe, S. Morita, R. Perez and O. Custance,Phys. Rev. Lett. 98, 106104 (2007).
[9] Y. Sugimoto, P. Pou, O. Custance, P. Jelinek, M. Abe, R. Perez and S. Morita,Science 322, 413 (2008).
[10] Y. Sugimoto, P. Pou, M. Abe, P. Jelinek, R. Perez, S. Morita and O. Custance,Nature 440, 46 (2007).
