Controlling film order to enhance the electrical properties of molecular diodes

We designed, developed and tested a series of benzalkylsilane molecules in self-assembled monolayers (SAMs) to investigate their degree of order and electrical properties when anchored to silicon substrates. The molecules consist of a silane anchoring group and a nitrogen-substituted benzene ring, separated by a propyl group and imine linkage. By varying fabrication procedures and the ring substituents, we obtained a vast range of rectification ratios, between 10-3100. The highest value was obtained for the molecule (E)-1-(4-cyanophenyl)-N-(3-(triethoxysilyl) propyl)methanimine. We assign the efficient rectification behavior to a highly ordered SAM and coupling between the delocalized lone pair of electrons from the nitrogen termination and the device electrode. These devices were employed for sensing applications allowing for sensitive detection of humidity. Overall, the utilization of these molecular devices will allow for functionable, cost efficient, and easily integrable devices.