Electrically-Driven Metal-Insulator Transitions Emerging from Localizing Current Density and Temperature

Abstract

Negative differential resistance (NDR) is a key electronic response enabling two-terminal artificial neurons that can be achieved through different physical phenomena, including phase-homogeneous current density and temperature (electro-thermal) localizations and spatially-localized metal-insulator phase transitions (MITs). These two effects have been observed to occur sequentially in select electrically-biased transition metal oxides. However, it is unknown why and under what conditions localizing behaviors precede MITs, particularly as a function of device length scale. To this end, the interplay between phase-homogeneous electro-thermal localizations and MITs is investigated in a 3D multiphysics simulation of a lateral thin film device, using the material properties of the prototype MIT material VO2. These findings demonstrate that the MIT is nucleated through dynamically localizing current density and temperature. A critical device width (≈0.7 µm in this study) is identified, below which both the electrically-induced electro-thermal and phase inhomogeneities cease to appear. It is demonstrated that the formation of spatial inhomogeneities directly relates to device dimensions, and demonstrate the decoupling of NDR from the MIT through device scaling relationships. These results provide insight into the material phenomena underlying the material's electrical responses, clarifying conditions under which spatial inhomogeneities form in electrically-biased MIT materials.