Scanning tunneling microscope-break junction (STM-BJ) technique has been widely used to investigate the single molecule junction and electron transport through the molecular electronics. With a continuing miniaturization of electronics, the development of highly insulating molecules is needed, where STM-BJ serves as the ideal platform for understanding nanoscale transport. The single-molecule conductance of silanes has been reported to be suppressed due to destructive quantum interference. However, designing and measuring highly insulating sub-nanometer short molecules is difficult because of exponentially increased coherent tunneling through the junction. Short insulating molecules that can further scale down the dimensions of the junction has therefore not been explored yet. Here, we present a new series of small molecules with short lengths that can hit the destructive quantum interference. Using STM-BJ technique, we confirm the single-molecule conductance of our proposed molecules to be extremely low, and verify the capability to be the molecular insulators. Calculations are carried out to support the existence of destructive quantum interference, rationalizing the suppression of conductance in the molecules and the behavior of the molecules to be insulators. We believe this work can chart a pathway for chemical design of short insulating organic molecules.

Novel molecular insulator with short length using destructive quantum interference

ACS Spring Meeting 2021

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