Correlation Between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts
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Correlation Between Quantum Conductance and Atomic Arrangement of Silver AtomicSize Nanocontacts Pedro A. Autreto1, Maureen J. Lagos1,2, Daniel Ugarte1, and Douglas S. Galvao1 1 Instituto de Física “Gleb Wataghin, Universidade Estadual de Campinas, Campinas - SP, 13083-970, Brazil 2 Laboratório Nacional de Luz Síncroton, Caixa Posta 6192, Campinas – SP, 13084-971 Brazil ABSTRACT In this work we have studied the importance of thermal effects on the structural and transport properties of Ag atomic-size nanowires (NWs) generated by mechanical stretching. Our study involve time-resolved atomic high resolution transmission electron microscopy imaging and quantum conductance measurement using an ultra-high-vacuum mechanically controllable break junction combined with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag NWs generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling, we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wires along the [001] crystallographic direction. INTRODUCTION The generation of atomic-size metal wires (nanocontacts) by mechanical stretching has allowed the study of a wide range of different metallic structures at nanoscale. Due to the dominant role of surface energy in this size regime, several new wire structures have already been experimentally observed during the mechanical stretching of very thin metallic films. These new structures include Ag hollow tubes and the spontaneously formation of complex atomic arrangements (pentagonal motifs linearly arranged) in Au-Ag alloys [1-3]. From the experimental point of view two techniques have been mostly used in the metallic nanowire (NW) investigations: mechanically controllable break junctions (MCBJ) [4-6] and in situ high-resolution transmission electron microscopy (HRTEM) [7]. MCBJ provides quantum transport data, but no direct structural information, while HRTEM provides structural information, but no direct transport data. The combined use of these two techniques has proven to be a very effective approach to help our understanding on the dynamics of NW formation, as well as, to establish a direct correlation between atomic arrangements and quantum conductance profiles [1-7]. Although significant progresses have been achieved on the understanding of NW properties, the majority of the available experimental data is related to Au-based wires. This is due in part to their easy sample preparation and manipulation. In order to obtain more broad-ranging insights, it would be desirable to investigate other model systems, as for example other metals with different surface properties (in order to induce different atomic structure during elongation). Ag represents an excellent candidate to these studies, because it is also a noble metal with iden
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