In Situ TEM Imaging of Defect Dynamics under Electrical Bias in Resistive Switching Rutile-TiO₂

Abstract

In this study, in situ electrical biasing was combined with transmission electron microscopy (TEM) in order to study the formation and evolution of Wadsley defects and Magnéli phases during electrical biasing and resistive switching in titanium dioxide (TiO2). Resistive switching devices were fabricated from single-crystal rutile TiO2 substrates through focused ion beam milling and lift-out techniques. Defect evolution and phase transformations in rutile TiO2 were monitored by diffraction contrast imaging inside the TEM during electrical biasing. Reversible bipolar resistive switching behavior was observed in these single-crystal TiO2 devices. Biased induced reduction reactions created increased oxygen vacancy concentrations to such an extent that shear faults (Wadsley defects) and oxygen-deficient phases (Magnéli phases) formed over large volumes within the TiO2 TEM specimen. Nevertheless, the observed reversible formation/dissociation of Wadsley defects does not appear to correlate to resistive switching phenomena at these length scales. These defect zones were found to reversibly reconfigure in a manner consistent with charged oxygen vacancy migration responding to the applied bias polarity.

In situ transmission electron microscopy of resistive switching in thin silicon oxide layers

“…Recently, in situ switching of RRAM devices in the TEM has been reported for a limited number of systems, most of which are metal-based. In these studies, filament formation resulted from the diffusion of metallic ions from the active electrode and was relatively easy to observe using conventional TEM techniques [13][14][15][16].…”

Anomalous Resistance Hysteresis in Oxide ReRAM: Oxygen Evolution and Reincorporation Revealed by In Situ TEM

“…As a result of its potential for atomic‐scale imaging of physical and chemical processes, there has recently been considerable progress in the development of in situ TEM using piezo‐controlled electrical probes and great interest in its application to memristive devices . Most previous reports on valence change memories have been based on the use of TEM or STEM imaging and diffraction.…”

Impact of intrinsic point defect concentration on thermal transport in titanium dioxide

“…where a 3 (13) where M De f is the mass of the defect and M Host is the average atomic mass of the host.…”

“…With increased concentration of point defects, thermal carrier propagation will be disrupted and local hotspots may lead to increased probability of device failure [10,11,12]. In the region of the electrodes of a dielectric material under prolonged electric fields, point defect concentrations can increase well beyond initial, homogeneous concentrations and lead to highly defective layers that can even move into entirely new phases from the severe non-stoichiometry [13,8].…”