Effect of anchoring atom and electrostatic gating on the electronic transport properties in single molecular electronic devices

Abstract

The effect of anchoring atom and electrostatic gate on the electron transport through gated thiophene single molecular device is studied by utilizing non-equilibrium Green’s function coupled with self-consistent extended Huckel theory. Gated gold–molecule–gold junctions are built using thiophene (Tp) molecule as functional component and sulphur (S) and selenium (Se) as anchoring atoms in field effect transistor (FET) configuration. The electron transport analysis of the gated thiophene single molecular device is investigated through the current–voltage and the electron transmission spectra. The results show that the anchoring atoms modulate the transport nature of these devices in a controlled manner. We find that the S–Tp–S device produces larger current than Se–Tp–Se device. Also we studied the effect of electrostatic gating on S–Tp–S and Se–Tp–Se device. We find that, positive bias or negative bias for V_g, will correspondingly, raise or lower the transmission coefficients T(E) in relation to the Fermi level (E_F) for both the devices. Our results show that magnitude of I_sd current varies more than one order for same V_sd over different V_g bias for S–Tp–S device, whereas for Se–Tp–Se device I_sd current varies more than five times for same V_sd over different V_g bias. Se–Tp–Se device shows gate controlled NDR behavior. Finally, we demonstrated the application of using thiophene based single molecular FET to realize five basic logic gates very low V_sd bias. The key feature of the suggested design is the opportunity of demonstrating various logic gates with just one molecular unit transistor and demonstrated at very low V_sd bias.