Full text loading...
The schematic structure of the molecular rotor device composed of a bisP stator, a copper metal axle, and a diimine rotator. The diimine ligand on top, 2,9-dimethyl-1,10-phenanthroline, rotates upon reduction and oxidation in the direction as illustrated with arrows.
characteristics of the monolayer device with the bisP stator. State “1” represents the low conductivity state, while state “2” is the high conductivity state. The turning voltage between state “1” and state “2” is determined by the redox energy of the copper system. The difference in value of the turning voltage between positive and negative ranges is due to the different contact energy barriers of the two electrodes. The arrows show the sequence of the voltage scan. Arrows “4” and “5” correspond to the band diagrams in Figs. 4(a) and 4(b), respectively (to be discussed later).
Arrhenius plot of the peak minus background current. The activation energy of rotation was extracted to be 0.3 eV by exponentially fitting the curve of the measurement data higher than 244 K. The inset shows the peak current as well as the background current at 0.5 V and −0.5 V, respectively. The weak temperature dependence of the background current implies tunneling transport of electrons.
Band diagram of the molecular rotor device under negative bias at (a) high conductivity state of Cu(I) system and (b) low conductivity state of Cu(II) system. As oxidation happens, one electron in the valence band tunnels out of the molecular layer and the energy states move down. The band gap increases so that the conduction path for electrons is closed, resulting in NDR.
Article metrics loading...