from 28 June 2015 to 3 July 2015 (Africa/Johannesburg)
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SAIP2015 Proceeding published on 17 July 2016
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Simulating mechanical annealing of atomic-sized gold surfaces via classical molecular dynamics and density functional theory transport calculations

Presented by Mr. Wynand DEDNAM on 1 Jul 2015 from 11:10 to 11:30
Type: Oral Presentation
Session: TCP
Track: Track G - Theoretical and Computational Physics

Abstract

The ability to probe interactions at the atomic level via scanning tunneling microscopy and other techniques has led to great interest in contact formation between atomic-sized metal electrodes [Agrait N et al. 2003 Phys. Rep. <b>377</b> 81]. For example, achieving ever smaller electronic circuit sizes is still a very important practical goal of nanotechnology [Lu Y et al. 2010 Nature Nanotechnology <b>5</b> 218]. In the present work, it is demonstrated by two complementary simulation techniques that atomic-sized gold surfaces can be sharpened reproducibly, or mechanically annealed, until they are stable and no longer change. Experimentally, stable sharp gold tips may be achieved by repeatedly indenting into a surface with the tip of a scanning tunneling microscope. Such a process can be simulated by classical molecular dynamics (CMD), which describes the dynamics of the gold atoms as the two atomic-sized surfaces make and break contact [Sabater C et al. 2012 Phys. Rev. Lett. <b>108</b> 205502]. To account for the interactions between the atoms in simulations, semi-empirical potentials fitted to various material parameters of the metals are used. The second simulation method, density functional theory (DFT) transport calculations [Palacios J J et al. 2002 Phys. Rev. B <b>66</b> 035322], serves to obtain the electronic properties of the CMD-simulated system, such as the transmission across the electrodes when they first make contact. This paper presents the CMD results of the repeated indentation of a gold tip into a flat gold surface, with and without adatoms on the surface beneath the tip. The quantized conductances of a large number of CMD snapshot configurations of these surfaces, at various points during the process of contact formation, are also presented. These results permit a better understanding and interpretation of the experimental observations.

Award

Yes

Level

MSc

Supervisor

Prof. BOTHA, Andre Erasmus (UNISA), Bothaae@unisa.ac.za

Paper

Yes

Permission

Yes

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