Charge storage behavior of nanowire transistors functionalized with bis(terpyridine)-Fe(II) molecules: Dependence on molecular structure

We studied the influence of three bis(terpyridine)-Fe(II) molecules(X-tpy)2FeCl2 (X = H (1), SAc (2), and 4-phenyl-SAc (3)on charge storage of a nanowire transistor. The molecules wereassembled on the surface of an indium oxide nanowire that forms the conduction channel of the transistor. We found that the charge storage characteristics of such a device strongly depends on the structure of the terpyridine ligand: both retention time (τ) and threshold voltage shift (ΔVth) increased in the order of 1 < 2 < 3, with τ of 200 s, 12 h, and 287 h and ΔVth at 4.8, 12, and 28 V, respectively. Furthermore, when we placed the devices with molecules 1 and 3 in a vacuum and recorded the I-Vg curves ina two-day period, we observed higher hysteresis stability for device with molecule 3. For example, ΔVth was reduced from 4.8 to 1.7 V for the device with molecule 1, while there was no reduction in ΔVth for the device with molecule 2. These results suggest that thiolate headgroup and/or longer ligand length raises the charge tunneling barrier and results in longer charge retention and wider, more stable memory window. This work demonstrates the potential of chemical synthesis toward tailored device characteristics. Copyright © 2004 American Chemical Society.