Mechanism of localized electrical conduction at the onset of electroforming in TiO2 based resistive switching devices

Abstract

The onset of localized current conduction during electroforming of TiO2-based resistive switching devices is investigated using a pulsed voltage method. The temperature rise at electroforming onset is found to vary from 25 to 300 °C as the pulse amplitude and the width are varied between 3–8 V and 10 ns–100 ms, respectively. The effective activation energy of the forming event is strongly electric field dependent and decreases from 0.7 eV at 3 V to almost zero at 8 V. The functional form of this dependence points toward charge trapping as the mechanism rather than oxygen vacancy motion.

Transient phases during fast crystallization of organic thin films from solution

“…By its nature, this model is applicable not just to chalcogenide glasses but to most amorphous semiconductors exhibiting NDR. Noman et al 16 presented the transient thermometry data, consistent with the filament formation based on charge trapping model originally proposed for breakdown in SiO 2 . 16 They argued that the charge trapping can give rise to a local electric-field enhancement eventually causing a breakdown.…”

“…17 This was confirmed experimentally in our TiO x and TaO x devices. 11 The filament, thus formed is volatile 16 as the I-V curves are fully reversible up to this point. While the temperature may increase during the initial thermal NDR beyond that of uniform heating, 11 the filament size at this stage is large and the temperature rise is limited to a range where it does not cause permanent changes in the device characteristics.…”

“…Similar arguments can be The temperature of the device right before threshold switching event was also simulated using the COMSOL Multiphysics finite element method solver for the range of stage temperatures. Simulation setup and the thermal parameters used have been discussed in our previous work 11,16 with the dissipated power taken from the experiment. The results were very similar to the temperatures extracted using the experimental procedure described above.…”

“…We have estimated this temperature using a thermometry approach discussed in detail in recent publications. 11,16 The true I(V, T) characteristics of the device have been obtained by measuring the voltage and current within the first 5 ns of a rectangular voltage pulse. In order to avoid reflections that typically obscure fast transients, the devices have been designed to be a matched 50 Ω waveguide in a ground-signal-ground configuration with the measurements performed by time domain transmissometry (TDT) method.…”

“…The process of threshold switching is not instantaneous and requires a certain incubation time before the device switches to the volatile ON-state (this state is different from the non-volatile ON state). 15,16 Incubation time in our devices was measured using TDT where the device under test was subjected to a series of rectangular pulses and the device voltage was monitored as a function of time (Fig. 3).…”