Negative differential resistance in memristive systems: historical evolution, mechanisms and neuromorphic applications of niobium oxide devices

The synergy between the memristive effect and negative differential resistance (NDR) offers promising prospects for advancing electronic devices and circuits. Predictable outcomes include the development of devices with improved performance and functionality that are applicable across a wide range of fields, from computing architecture to neuromorphic engineering. Despite the growing body of literature exploring this convergence, the effective implementation of the NDR effect in memristors faces many challenges. Several memristive materials-including VO₂, TaO_<i>x</i>, and chalcogenides-have demonstrated promising NDR effects. Among them, niobium oxide uniquely combines steep (<3 ns), endurable (>10¹² cycles) negative differential resistance with biophysically plausible spiking dynamics-enabled by its dual current-controlled and thermally driven mechanisms-making it ideal for energy-efficient neuromorphic primitives. This paper reviews the complex phenomenon of NDR and its applications in niobium oxide memristors while analyzing its potential future applications in electronic systems. By outlining the NDR effect and its applications in niobium oxide memristors, this paper aims to provide valuable insights for researchers in the field.