Dipole tuning of charge transport in molecular junctions

Abstract

Molecules with different magnitude and direction of dipole moments are sandwiched between mercury (Hg) and p⁺-Si to form Hg–molecules–(p⁺) Si junctions. The importance of the dipole moment of molecules in controlling the symmetry of current–voltage curves is shown by carrying out charge transport measurements at these molecular junctions. Junction parameters are obtained by considering charge transport across the junction as a combination of tunneling and Schottky emission. An interesting effect due to dipole reversal resulting in rectification of junction curves in the opposite quadrants of the current–voltage axis is observed and analyzed. The junction curves also exhibit a different degree of rectification with increasing magnitude of the dipole moment of the sandwiched molecules.