A2 Correlation between the atomic structure and electronic states in resistively switching oxides

Project A2 (2019-2023) aims for the elucidation and quantification of spatial changes in the electronic and atomic structure taking place during repeated VC switching in order to determine the microscopic switching and failure mechanisms in dedicated binary and ternary oxide cells. Based on this knowledge, we will develop strategies to improve the reliability of VCM cells by rational materials design and the use of tailored processing conditions. By engineering cells with different switching modes identified in the third SFB period (8W, C8W, filamentary, area-dependent), we are aiming to overcome the limiting trade-offs of current filamentary memory cells.


The aim of the project is to elucidate the correlation between the resistive states in selected valence change systems (SrTiO3, Ta2O5 and HfO2) and changes of the atomic and electronic structure. We will employ grazing incidence small angle X-ray scattering as well as different spectromicroscopic approaches based on X-ray absorption and X-ray photoelectron emission. The in operando use of these techniques will enable us to study spatial changes of the electron density, the valence, the stoichiometry and the phase during device operation and failure. This analysis will provide us with the key knowledge about the switching and failure mechanisms of VCM materials.



Aim of this project is a concerted clarification of stoichiometric, valence and structural changes induced during electroforming and switching in thermo-chemical (TC) and valence change (VC) transition metal oxides. We are developing methods to employ synchrotron-based X-ray scattering (GISAXS) techniques to study the filament formation, comparing the results to electron microscopic analysis (see project Z2) and supplementing these studies by advanced photoemission spectroscopy and -spectromicroscopy studies (see project B6). We accompany the experiments by a theoretical description of the energy landscape of the potentially formed phases using a first-principles model of realistically large oxide systems based on a massively parallelized algorithm.

Principal investigators:

Prof. Dr.-Ing. R. Waser
Institut für Werkstoffe der Elektrotechnik 2
RWTH Aachen University
Phone: +49 (0)241 80 27812
E-mail: waser@iwe.rwth-aachen.de

Prof. Dr. rer. nat. R. Dittmann
Peter Grünberg Institut (PGI-7)
Forschungszentrum Jülich GmbH
Phone: +49 (0)2461 61 4760
E-mail: r.dittmann@fz-juelich.de

Prof. Dr. rer. nat. U. Klemradt
II. Physikalisches Institut B
RWTH Aachen University
Phone: +49 (0)241 80 27075
E-mail: klemradt@physik.rwth-aachen.de

Prof. Dr. rer. nat. M. Ležaić
Peter Grünberg Institut (PGI-1) and
Institute for Advanced Simulation (IAS-1)
Forschungszentrum Jülich GmbH
Phone: +49 (0)2461 61 5369
E-mail: m.lezaic@fz-juelich.de