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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 28: Focus Session: (Multi-)Ferroic States IV
KFM 28.4: Talk
Thursday, March 21, 2024, 16:10–16:30, EMH 225
Localized oxygen reorganization under sub-millisecond switching in ferroelectric epitaxial hafnia-based films — •Nives Strkalj1,2, Megan O. Hill2, Ji Soo Kim2, Moritz L. Müller2, Maximilian T. Becker2, Dibya Phuyal2,3, Sunil Taper2, Manisha Bansal4, Babak Bakhit3, Tuhin Maity4, Giuliana Di Martino3, and Judith L. MacManus-Driscoll3 — 1IoP, Zagreb, Croatia — 2UCAM, UK — 3KTH, Sweden — 4IISER TVM, India
The discovery of ferroelectricity in nanoscale films of binary oxides based on hafnia spurred renewed interest in the emergence of ferroelectric properties on the nanoscale. The unusual size dependence of polarization in hafnia is a topic of intense research with explanations including flat phonon bands, and coupling to an antipolar phase or an electrochemical state. Though polarization switching and electrochemical reactions have been shown to co-occur in hafnia-based films, their relationship remains unclear.
To elucidate the relationship between the polarization state and the electrochemical state, we perform direct observations of the electrochemical state in areas with preset polarization directions for hafnia-based films using hard x-ray photoelectron spectroscopy (HAXPES). Because we observe more pronounced electrochemical changes in films with lower polarization, we propose that the polarization and the electrochemical change are not directly linked. Our results present a step forward in disentangling the origin of the ferroelectric response in hafnia-based films.
Keywords: ferroelectricity; nanoscale; hafnia; hard x-ray photoelectron spectroscopy; electrochemical state