Oxide‐based resistive switching devices are a leading contender for the next generation memories. Before use, each device has to go through a conditioning process called electroformation which has been suggested to be initiated by the accumulation of oxygen vacancies. Here, experimental evidence is presented which shows that both Ta2O5‐x‐ and TiO2‐x‐based crossbar devices, exhibit characteristic electronic instability leading to a reversible constriction of the current flow to a narrow filament prior to permanent change. Thus, it is asserted, electroformation is initiated through purely electronic and reversible events, to be followed later by structural changes in the material, like oxygen vacancy redistribution. Furthermore, the electronic instability responsible for electroformation also gives rise to negative differential resistance (NDR) and that this characteristics appears to involve two distinct mechanisms: a thermal one in which Joule heating causes resistance to decrease as current increases and a second electronic mechanism that appears not to require Joule heating for NDR. Using a combination of thermometry and thermal modeling, a self‐consistent temperature and filament radius as a function of power are found for the 5 μm cross‐bar devices. In the thermal NDR regime, the filament appears to be ∼500 nm in diameter and has a peak temperature of ∼300 °C, while in the adiabatic regime, the estimated filament diameter is much smaller (<50 nm) and the maximum temperature inside it exceeds 800 °C.

Capacitance−voltage characteristics of high quality Pt Schottky diodes fabricated on oxygen-vacancy-doped SrTiO3 single crystals were used to obtain the oxygen vacancy profiles within one microns of the Pt interface. Computer simulations based on solving the drift-diffusion equations for electrons and ionized vacancies were performed to understand the experimentally observed oxygen vacancy profile’s time-evolution at room temperature and 0 V applied bias. Building upon this understanding, the diode’s room temperature profile evolution under −35 V applied bias was analyzed to yield a vacancy mobility value of 1.5 × 10−13 cm2/V·s at an electric field of 500 kV/cm. This mobility is 8 orders of magnitude too low to produce nanosecond resistance switching in thin film devices. The applicability of the results to oxygen-migration-based resistance switching is discussed relative to recent observations and modeling.

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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.