Gating the Rectifying\nDirection of Tunneling Current\nthrough Single-Molecule Junctions

In electronic functional chips, one of the most crucial\ncomponents\nis the field-effect transistor (FET). To meet the urgent demands for\nfurther miniaturization of electronic devices, solid-state single-molecule\ntransistors by molecular orbital gating have been extensively reported.\nHowever, under negative bias and positive bias, achieving a distinct\ngating effect is extremely challenging because molecular orbital gating\nis independent of the bias polarity. Here, we demonstrated that rectifiers\ncan be realized in single-molecule junctions with a symmetric molecular\nstructure and an electrode material by simply breaking the symmetry\nof the electrode’s chemical potential via ionic adsorption.\nWe further demonstrated that the tunneling current can be gated with\nopposite change tendencies under negative and positive bias by applying\nan ionic gating voltage, which eventually results in a reversal of\nthe rectifying direction. Our experiments elucidate that, unlike the\nclassical mechanism for solid molecular FET, the modulation of the\nelectrode's chemical potential, rather than the regulation of\nmolecular\norbitals, might dominate the electron transport in the ionic liquid\nenvironment upon a gating voltage. Our study gains deeper insights\ninto the mechanism of ionic liquid gating and opens a window for designing\nhigh-performance electrochemical-based functional devices.