We tested the electrical characteristics of an oligo(phenylene ethynylene) (OPE) molecule with one nitro side group, an OPE with two nitro side groups, and an OPE with no nitro side groups in our nanowell device. The OPE molecule with nitro side group(s) showed switching behavior with memory as well as nonreversible negative differential resistance (NDR). Current-voltage (I-V) characteristics showed a high conductivity state that switched to a low conductivity state upon the application of a threshold voltage. This low state held until the opposite threshold voltage was applied and the device switched back to the high conductivity state. The OPE with no nitro side groups did not show memory or NDR. In this work, we report the complete switching behavior observed including the device yield, average threshold voltage, and the average high to low current ratios. (c) 2005 American Vacuum Society.