Quantum Mechanical Simulation of Defect Migration and Phase Transition Dynamics Unterlying Resistive Switching in TiO2

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Memristors are passive electronic elements, the ohmic resistance of which can be switched between different stable states by an externally applied current. Because these states remain stable, even if the external current is switched off, memristors are especially suitable to replace flash memory cells for use as nonvolatile memory. Resistive random access memory (RRAM) memory cells would be significantly cheaper and smaller than complex, transistor based flash memory. However, the microscopic mechanisms underlying the memristive behavior of technically relevant oxide materials are so far not understood well enough to allow knowledge-based engineering. The improvement of RRAM devices is hindered by a lack of basic understanding of the resistive switching mechanism. Experimental data indicate that in memristors manufactured from oxygen deficient oxide materials, conducing filaments are formed and dissolved, connected to the migration of oxygen deficiency related defects. In TiO2, which is of particular technological interest, the migration of oxygen atoms and vacancies is assumed to be of crucial importance. In the proposed project, atomically resolved quantum simulations of the dynamics of point defect migration in TiO2 under the driving forces of external electric field and temperature gradients shall be pursued together with dynamic simulations of oxygen vacancy ordering in TiO2−x. An empirical model of the resistive switching mechanism in oxygen deficient TiO2 shall be developed to enable knowledge based RRAM engineering.