Oxygen Vacancy Dynamics in Different Switching Modes of Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2-δ</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 40767388.
- Also identified by DOI 10.1021/acsnano.5c07038 and PMC identifier 12368994.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
HfO<sub>2</sub>, one of the most common materials in resistive switching devices, can stabilize in a ferroelectric orthorhombic phase, enabling two nonvolatile polarization states via oxygen displacement in the unit cell. Under certain conditions, ferroelectric and resistive switching can coexist, independently addressable, within one device. This study employs <i>operando</i> spectroscopic analysis to elucidate the role of oxygen in both switching processes. A conductive filament is identified through a local valence change at the oxide surface via X-ray Photoelectron Emission Microscopy, allowing vacancy density and filament diameter evaluation. This provides well-founded experimental evidence of a conductive filament in orthorhombic Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2-δ</sub> (HZO) in application-relevant device geometry. Depth-dependent changes in the electronic signature of HZO and La<sub>0.8</sub>Sr<sub>0.2</sub>MnO<sub>3-δ</sub> (LSMO) with ferroelectric field cycling are identified by Hard X-ray Photoelectron Spectroscopy. Polarization-dependent shifts in the Hf core level align with the oxygen vacancy migration during ferroelectric switching. Fatigue-related vacancy generation causes an inhomogeneous reduction that does not propagate into the bottom electrode and extended domain pinning at the HZO/LSMO interface. This highlights the importance of interface engineering for the ferroelectric performance and of the oxygen affinity of the bottom electrode for both switching regimes.