Tetrathiafulvalene-based nanocrystals: site-selective formation, device fabrication, and electrical properties

A tetrathiafulvalene (TTF)-based nanocrystal was site-selectively synthesized only in the gap between two electrochemical electrodes by using a nanoscale electrocrystallization method. Furthermore, the nanocrystal was directed to form a bridge between two electrodes using alternating current (AC) electrolysis. The nanocrystal was found to have a one-dimensional π-π stacking structure of TTF molecules, which is the source of its high electrical conductivity. Further, when we reused the two electrochemical electrodes as the source and drain electrodes, a two-terminal device could be readily obtained. The electrical conductivity of the nanocrystal was comparable to that of a partially oxidized bulk crystal. A bottom-gate-type FET was also obtained when the device was fabricated on a silicon substrate. A weak field effect was observed even though the nanocrystal has a metallic nature. The nanoscale electrocrystallization is considered to be applicable to nanocrystal fabrication using various organic molecules. We expect that further enhancement of this method will lead to the development of eco-friendly nanofabrication processes. A tetrathiafulvalene (TTF)-based nanocrystal was selectively synthesized only in the gap between two electrodes using a nanoscale electrocrystallization. A two-terminal TTF-based device and an FET could be readily obtained via an eco-friendly nanofabrication process.