Negative differential resistance in molecular junctions

The occurrence of negative differential resistance (NDR) in the molecular junctions (MJs) is one of the fascinating phenomena in the field of molecular electronics (ME) characterized by a decrease in current with an increase in voltage. This inverse behaviour to Ohm's law gained prominence taking ME to the next generation, which includes neuromorphic computing, ultra-low power switches, high frequency oscillators, sensors and memory devices. This phenomenon in MJs is influenced by some key parameters, such as asymmetry in electrodes, coulomb blockade, charging effects, conformational changes in the molecules, redox reactions and the interface coupling (at molecule-electrode interface). This review covers the fundamental mechanisms of NDR and highlights several experimental and theoretical observations and finally discusses about the commercialization of NDR devices along with the challenges and future perspectives. By observing and understanding the advances of the NDR phenomenon, we can achieve the scalable, reproducible and stable NDR-based devices which enable us to step into the next generation of nanoelectronics devices.