Electric Field Driven Dual-Functional Molecular Switches in Tunnel Junctions

To avoid cross-talk and suppress leakage currents in resistive random access memories (RRAM), a resistive switch and a current rectifier (diode) are usually combined in series in a one diode—one resistor (1D-1R) RRAM. However, this complicates the design of next-generation RRAM, increases the footprint of devices, and increases the operating voltage as the potential drops over two consecutive junctions. Here we report a molecular tunnel junction based on molecules that provide an unprecedented dual functionality of diode and variable resistor resulting in molecular-scale 1D-1R RRAM with current rectification ratio = 2.5×104 and resistive on/off ratio = 6.7×103, and a low drive voltage of 0.89 V. The switching relies on dimerization of redox units, resulting in hybridization of molecular orbitals accompanied by directional ion migration. This electric field driven molecular switch operating in the tunneling regime enables a class of molecular devices where multiple electronic functions are preprogrammed inside a single molecular layer with a thickness of only 2 nm.