Dependency of the Tunneling Decay Coefficient in Molecular Tunneling Junctions on the Topography of the Bottom Electrodes

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.