Dependency of the tunneling decay coefficient in molecular tunneling junctions on the topography of the bottom electrodes

Abstract

A controversy in molecular electronics is the unexplained large spread in values of the tunneling decay coefficient β in tunneling junctions with self-assembled monolayers of n-alkanethiolates (SCn). We show control of the β value over the range 0.4-1.0 nC -1 in junctions by changing the topography of the bottom electrodes that support the SAMs. Very low β values (0.4-0.5 nC -1) are obtained for rough surfaces with large areas of exposed grain boundaries, while β=1.0 nC -1 for smooth surfaces with small areas of exposed grain boundaries. Taking the rough with the smooth: The tunneling decay coefficient β in tunneling junctions with self-assembled n-alkanethiolate monolayers can be controlled by changing the topography of the bottom electrodes. Rough surfaces with large areas of exposed grain boundaries give β=0.4-0.5 nC -1, while smooth surfaces with small areas of exposed grain boundaries give β=1.0 nC -1 (see picture). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.