Imaging of Electrothermal Filament Formation in a Mott Insulator

Abstract

The high-power consumption caused by Joule heating is one reason for the emergence of the research area of neuromorphic computing. However, Joule heating is not only detrimental. In a specific class of devices considered for emulating firing of neurons, the formation of an electro-thermal filament sustained by locally confined Joule heating accompanies resistive switching. Here, the resistive switching in a V2O3-thin-film device is visualized via high-resolution wide-field microscopy. Although the formation and destruction of electro-thermal filaments dominate the resistive switching, the strain-induced coupling of the structural and electronic degrees of freedom leads to various unexpected effects like oblique filaments, filament splitting, memory effect, and a hysteretic current-voltage relation with saw-tooth like jumps at high currents. Main Text:The strongly correlated electron system (SCES) V2O3 is a prototypical Mott-Hubbard insulator [1]. At room temperature, stoichiometric V2O3 is a paramagnetic metal with corundum structure, which undergoes a metal-to-insulator-transition (MIT) in cooling below about 150 K. The insulating phase is antiferromagnetic with monoclinic structure.Upon heating the insulating phase undergoes an insulator-to-metal-transition (IMT) [2][3][4]. In recent years, there has been a growing interest in the resistive switching of SCES-devices [5].

Universal size-dependent nonlinear charge transport in single crystals of the Mott insulator Ca$_2$RuO$_4$

“…An example of this was found in V 2 O 3 , [45] which exhibits an IMT similar to Ca214, albeit at lower temperatures (150 K). For Ca214, Zhang et al [16] inspected phase separation in the intermediate current state using scanning near field optical microscopy (SNOM) and found the formation of the metallic phase in a striped pattern along some current directions.…”

Nanoelectronics Using Metal–Insulator Transition

“…In addition to this, transmission electron microscopy (TEM) technology will also be required to analyze the phases. [ 225,255,256 ] Orbital engineering by controlling the defect creation, which can be generated by lattice strain, interface engineering, or doping element, may increase the sensitivity of electrical stimulus in Mott insulators, modulating the phase coexistence properties. Despite some volatile properties of the Mott insulators, [ 257 ] these orbital engineering approaches can be considered formulated methods that can induce the nonvolatility in a Mott insulator itself.…”

“…In addition to this, transmission electron microscopy (TEM) technology will also be required to analyze the phases. [ 225,255,256 ]…”

Quantum imaging of the reconfigurable VO 2 synaptic electronics for neuromorphic computing

“…On the other hand, electric field-induced IMT in a two-terminal device constructed by VO 2 films can produce the filamentary conducting channel from the original insulation layer. The conducting filament has been imaged on the basis of the distribution of temperature, crystal phase, or optical reflectivity (16)(17)(18)(19)(20). The quantum sensor based on a nitrogen-vacancy (NV) center in diamond enables synchronous measurement of local magnetic field and temperature on VO 2 film, providing an unusual insight into the field-induced IMT (25,37).…”

“…Because of the strongly correlated property, the insulator-metal transition (IMT) in Mott materials induces a huge change in resistivity, and it can be triggered by electric field, enabling applications on artificial synapses (15)(16)(17)(18)(19)(20). Selective phase transition based on the external stimuli manipulates the formation of the conducting filament although its location is still unchangeable (21).…”