Kiel Nano, Surface and Interface Science (KiNSIS)

Uncovering switching and failure mechanism in memristive devices by in-situ spectromicroscopy (Regina Dittmann, Forschungszentrum Juelich GmbH & RWTH Aachen University)

Apr 22, 2021 from 04:00 PM to 05:00 PM

Online

Logo CRC 1461Dr. Regina Dittmann

Peter Gruenberg Institute 7, Forschungszentrum Juelich GmbH & RWTH Aachen University

 

Abstract

It is generally assumed that voltage-driven oxygen-ion migration and the resulting nanoscale redox processes drive the resistance change in transition metal oxide based memristive devices. Direct observation of the switching and failure mechanism, however, remain challenging because the net changes of structure, stoichiometry, and valence state during switching are very small and occur primarily at electrode interfaces or within nanoscale filaments.
Here we will present local changes in the chemical and electronic structure of SrTiO3-based memristive devices utilizing high-resolution operando characterization tools like transmission electron microscopy (TEM) and photoemission electron microscopy (PEEM). We chose SrTiO3 as a single crystalline model material, which offers a well-understood platform and well-characterized spectroscopic signatures.
To overcome the surface sensitivity typically limiting PEEM investigations of memristive devices, we either delaminated the top electrode in-situ [1] or employed photoelectron-transparent graphene top electrodes were used to attain spectroscopic information from the buried SrTiO3 layer [2]. We could thereby determine the position of in-gap states within the SrTiO3 filaments and use it as input for our calculations of the electronic transport [3]. Quantitative maps of the oxygen vacancy concentration obtained during in situ switching confirm that localized oxygen evolution and reincorporation reactions rather than purely internal movement of oxygen vacancies cause the resistance change. A remarkable agreement between experimental quantification of the redox state and device simulation reveals that changes in oxygen vacancy concentration by a factor of 2 at electrode-oxide interfaces cause a modulation of the effective Schottky barrier and lead to >2 orders of magnitude change in device resistance [2].
Moreover, in-situ PEEM analysis enabled us to identify the microscopic origin of retention failure in SrTiO3 devices [1] and to reveal two different mechanisms for the cycle-to-cycle variability of our devices, namely the change of the shape of the filaments and the movement of filaments during cycling [4].

Download the abstract as pdf-file

The talk takes place within the colloquium of the CRC 1461 "Neurotronics: Bio‑inspired Information Pathways", everybody interested is cordially invited. https://uni-kiel.zoom.us/j/84603911951?pwd=cHRjemtqT3FzZUVjcFlQdzMvOTJIQT09
Meeting ID: 846 0391 1951, Passcode: 120422

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