Dipole tuning of charge transport in molecular junctions.

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.