Characterization of electron conduction in unsaturated organic monolayers on silicon(111) using electrical impedance spectroscopy

Abstract

Electrical impedance spectroscopy (EIS) studies of monolayers comprised of molecules of Geranyllinalool and Isophytol revealed structural and molecular organizational details that were compatible with crystallographic dimensions of these molecules. Geranyllinalool (C20H34O) and Isophytol (C20H40O) differ principally in the structures of their hydrocarbon backbones. Several carbon-carbon bonds in the Geranyllinalool backbone are double bonds (unsaturated) whereas those bonds in Isophytol are single (saturated). Even though the Geranyllinalool monolayers were thicker than the Isophytol monolayer, EIS further revealed that their conductivities were an order of magnitude higher than those of the Isophytol monolayers. This is consistent with the electron enriched double bonds in the Geranyllinalool backbone providing a better conduction path than the electron depleted single bonds in the Isophytol backbone. The study reveals that unsaturated organic monolayers can improve the electrical connectivity of the semiconductor- biological interface whilst maintaining biocompatibility and passivity. © 2009 Springer-Verlag.