Tuning of electron tunneling: a case study using BODIPY molecular layers.

Redox active π-conjugated organic molecules have shown the potential to be used as electronic components such as diode and memory elements. Here, we demonstrate that using simple surface chemistry, rectification characteristics can be tuned to reproducible negative differential resistance (NDR) with a very high peak-to-valley ratio (PVR) up to 1000 in 2,6-diethyl-4,4-difluoro-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indecene (BODIPY) grafted on Si. The change in properties is related to oxidation and reduction of BODIPY, which results in the change in resonant to non-resonant tunneling of electrons under bias. This has been explained by the ab initio molecular-orbital theoretical calculations.