Fabrication and Characterization of Interconnected Nanowell Molecular Electronic Devices in Crossbar Architecture

The implementation of circuit architectures based on molecular electronic devices has been impeded by the availability of facile fabrication schemes for the interconnection of individual devices. The deposition and patterning of a top contact layer between adjoining devices for interconnection purposes can result in contacts of poor fidelity, which introduces artifacts in the I-V characteristics that are not attributable to molecular transport between the contacts. In this study, through the fabrication of interconnected devices within the crossbar device architecture, we demonstrate that the vapor-phase molecular deposition method for fabrication of device layers was compatible with the massively parallel microelectronic fabrication process of liftoff, for patterning of contact layers. A prepatterned device with Au bottom contacts, as well as a bilayer resist for patterning the top Au contacts through postdeposition liftoff was used as the substrate for vapor-phase deposition of a monolayer of conjugated oligo-(phenylene ethynylene) (plain-OPE) molecules and patterning of the top metal contact layer. Interconnection in series and parallel configurations was confirmed by I-V characteristics similar to classical resistors with equivalent conductivity of each individual molecular device. Additionally, to better understand molecular transport in the device junctions, we performed temperature-dependent I-V studies on individual molecular devices that were fabricated using prepatterned Au bottom contacts as the substrate for solution-phase deposition of the molecular monolayer, onto which the Au top contacts were evaporated and patterned using a shadow mask. Molecular layers of two distinctly different room-temperature I-V characteristics, including nonswitching plain-OPE and switching nitro-OPE molecular devices, were used to study the fidelity of the molecular junctions. Based on the persistence of the device characteristics of both types of molecular layers down to 100 K, and in particular, the observation of switching between "high" and "low" conductivity states at characteristic threshold voltages at all temperatures, only with nitro-OPE molecular devices, and not with plain-OPE molecular devices, we conclude that the observed transport was a characteristic molecular signature not dependent on filament formation at contacts.