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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 11: (Multi)ferroic States: From Fundamentals to Applications (V)
KFM 11.4: Vortrag
Mittwoch, 19. März 2025, 10:30–10:45, H9
Ranges and limits of p-doping in Y:HfO2 - an electronic structure study by HAXPES — •Oliver Rehm1, Lutz Baumgarten2, Florian Wunderwald3, Andrei Gloskovskii4, Christoph Schlueter4, Thomas Mikolajick3,5, Uwe Schroeder3, and Martina Müller4 — 1Universität Konstanz — 2Forschungszentrum Jülich — 3NaMLab, Dresden — 4DESY, Hamburg — 5TU Dresden
Ferroelectric HfO2-based thin films exhibit huge potential for the next generation of nonvolatile memory applications, such as FeRAM or FeFET. However, the application of HfO2-based thin films as active ferroelectrics (FE) in devices still faces reliability issues like wake-up, imprint, and fatigue. A critical concentration of oxygen vacancies (OVs) determines both the stabilization of a FE phase as well as the breakdown during electrical cycling. For p-doped HfO2, the electronic limits of OV formation remain an experimentally open question.
We investigated Y:HfO2 samples synthesized via atomic layer deposition (ALD) with Y doping concentrations from 2.1% to 8.6%. TiN/Y:HfO2 interfaces are investigated regarding the local chemistry and electronic properties by hard X-ray photoelectron spectroscopy (HAXPES). The Hf 4f core level is analyzed to identify Hf3+ components and rigid binding energy (BE) shifts, both of which serve as indicators for OVs. We determine the (unexpected) formation of OVs as a function of Y doping, with the conclusion that Y doping above a threshold limit has a detrimental effect on interface stability, thereby promoting increased OV formation at the interface that finally speeds up fatigue and breakdown.
Keywords: HAXPES; oxygen vacancies (OVs); Y:HfO2; Hafnia; ferroelectric