Beyond the Electrostatic Gate in a Single-Molecule Transistor

Transistor amplification properties of a three-leg spirofluorene-based molecule are investigated, and the transistor is shown to possess usable current, voltage, and power gain. Current gain is facilitated since the source-drain legs are conjugated, whereas the gate (control) leg is unconjugated and spatially orthogonal, and voltage gain is enhanced by the efficient quantum-mechanical coupling to the gate. Full quantum-mechanical calculations were done for all three electrodes, using the density functional formalism and a plane-wave decomposition of the wave functions.