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CCS&M seminar - Regina Dittmann: Oxide based memristive devices: current status of understanding and future prospects

Wanneer:di 26-09-2017 15:00 - 16:00

Transition metal oxides exhibit a reversible, non-volatile change in electrical resistance upon electrical stimulus, a phenomenon known as resistive switching. In the simplest case resistive switching memory cells, or so called memristive devices, can be switched between a low resistance state (LRS) and a high resistance states (HRS) which can be interpreted as the logical "1" and "0", respectively. However, it is important to note that resistive switching cells often show multiple resistive states rather than only two logical states.

Based on the current knowledge, resistive switching in memristive elements based on transition metal oxides can be ascribed to electrically induced redox-processes at the oxide/electrode interface, which occur either in a spatially confined switching filament, multiple filaments or in a spatially homogeneous, area-dependent manner. In most cases, the redox-process in the metal-oxide goes along with a change in the valence state of the metal ion modifying the Schottky barrier at the oxide/electrode interface. Therefore, this type of switching mechanism is also called valence change mechanism (VCM).

In this talk, we will present the current knowledge about microscopic mechanisms which drive electroforming and resistive switching in different variants of VCM-type memristive elements. In particular, we will show direct experimental evidence of the redox-processes gained by in-operando spectroscopy and microscopy. Using the quantitative numbers gained from these experiments as input for existing nanoionic device simulations offers a route to less empirical and more predictive design of future memory cells. We will present detailed experimental studies and simulations of the strongly non-linear switching kinetics based on the drift-diffusion processes of oxygen vacancies in VCM-type systems. Finally, a brief overview about the current and future fields of application will be presented.