Electronic properties associated with conformational changes in azobenzene-derivative molecular junctions

The electronic properties of azobenzene-derivative ([4-(phenylazo)phenoxy]hexane-1-thiol) molecular junctions were studied in terms of their molecular configurations with vertical device structure as solid-state device platform. This molecule has two distinct molecular configurations (trans- and cis-isomer) depending on the wavelength of irradiating light, which converts from more thermodynamically stable trans-isomer to cis-isomer under UV exposure (similar to 365 nm) and reversible photoisomerization of cis-isomer to trans-isomer under visible light (400-500 nm). The two states showed that the conductance of cis-isomer (compact form) was higher than that of trans-isomer (extended form). From the temperature-variable electrical characterization, the main charge conduction mechanism for the two isomers was found to be tunneling. And, from the transition voltage spectroscopy analysis and ultraviolet photoelectron spectroscopy measurement, the origin of such result can be explained by reduction of molecular tunneling distance between two isomers. (C) 2011 Elsevier B. V. All rights reserved.