Electronic Conduction in Ti/Poly-TiO2/Ti Structures

Abstract

Recent intensive investigations on metal/metal oxide/metal structures have targeted nanometric single grain oxides at high electric fields. Similar research on thicker polycrystalline oxide layers can bridge the results to the prior literature on varistors and may uncover novel ionic/electronic features originating from the conduction mechanisms involving grain boundaries. Here, we investigate electronic conduction in Ti/poly-TiO2−x/Ti structures with different oxygen vacancy distributions and describe the observed features based on the motion and rearrangement of the ionized oxygen vacancies (IOVs) on the grain facets rather than the grain interiors. Containing no interface energy barrier, Ti/poly-TiO2/Ti devices demonstrate high resistance ohmic conduction at biasing fields below 5 × 106 V.m−1; higher fields drive the samples to a distinctly nonlinear and hysteretic low resistance status. The observed threshold is two orders of magnitude smaller than the typical resistance switching fields reported for the nanosized single grain memristors. This is consistent with the smaller activation energies reported for the IOV motion on the rutile facets than its interior. The presented model describes the observed dependence of the threshold field on the relative humidity of the surrounding air based on the lower activation energies reported for the hydroxyl-assisted IOV motion on the rutile facets.

Electrical characteristics of interfacial barriers at metal—TiO2 contacts

“…The contribution of internal point defectrelated ionic motions [47,48] and/ or those originating from the electrodes should also be taken into consideration. In particular for TiO 2 films, the Ti/TiO 2 /Ti stack appears to be very useful for these studies as it allowed for a detailed assessment of the core material controlled con duction mechanism [49,50]. The latter is supported by our results, as Ti was found to form ohmic or nonrectifying con tact when used both as a TE and as a BE.…”

“…This further supports our argument that electrode materials should always be selected in pairs. Moreover, each material should be carefully consid ered with respect to its use as a TE or BE; although in some cases, such as Ti, no rectifying barrier is formed for either con figuration, rendering the Ti/TiO 2 /Ti system as the most suitable with which to study the filmcontrolled transport [50].…”

Experimental demonstration of highly reliable dynamic memristor for artificial neuron and neuromorphic computing

“…2f ). The calculated activation energy ( E A ) is about 0.21 eV, which is similar to the activation energy of the ionized oxygen vacancy in polycrystalline H 2 O-rich TiO 2 19 . The calculated activation energy of the gradual TiO x memristor is much smaller than the oxygen diffusion activation energy (1.05 eV) in rutile TiO 2 20 .…”

Effect of Reinforcing Particle Shape on the Behavior of Composites Materials

“…The bonding of particle-matrix can be improved by increasing the contact surface area between the matrix and reinforcement [13], and the same can be said about nanocomposites, when the particle diameter decreases, the contact surface area increases. The ultimate strength strongly depends on the stress transfer between the particles and the matrix [14]. Factors like type, size distribution, agglomeration state/dispersion, chemical deposition, crystal structure, surface area, surface chemistry, surface charge, shape/morphology, dissolution/solubility, physical/chemical properties of nanoparticles affect the properties of composite materials [15].…”