V. K. Lamba, O. P. Garg

Global College of Engg & Tech Khanpur Khui

 

Molecular junction is a promising candidate for devices nowadays. Great effort has been devoted recently to understand the role of the symmetry in the transport properties of molecular junctions. However, these studies have been largely based on the analysis of the low-bias conductance, which does not allow to elucidate the exact influence of the symmetry in both the electronic structure and transport characteristics of the junctions. In this work we present a theoretical study of the transport properties, and how conductance changes with symmetry. Herein, we investigate an anthracene-dithiol, and anthracene-dicyano single-molecule system in which sulphur and cyano group from the molecule are anchored to two facing gold electrodes. We have performed first principles calculations of the transport properties of these molecules using a combination of density functional theory and non-equilibrium Green's function techniques. Our computational results show that all anthracene isomers have similar energy gaps and molecular orbital levels, anchored with sulphur and cyano groups. The variation of conductance can be explained due to the difference in the frontier molecular orbital phases of the two anchored groups with the electrodes. Thus the orbital symmetry rule for charge transport in a molecular junction provides a rule for the design of molecules that exhibit known value of conductance.

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