TY  - JOUR
AU  - Rushchanskii, Konstantin
AU  - Blügel, Stefan
AU  - Ležaić, Marjana
TI  - Ordering of Oxygen Vacancies and Related Ferroelectric Properties in HfO 2 − δ
JO  - Physical review letters
VL  - 127
IS  - 8
SN  - 0031-9007
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2021-05040
SP  - 087602
PY  - 2021
AB  - Using density functional theory combined with an evolutionary algorithm, we investigate ferroelectricity in substoichiometric HfO2−δ with fixed composition δ=0.25. We find that oxygen vacancies tend to cluster in the form of two-dimensional extended defects, revealing several patterns of local relative arrangements within an energy range of 100 meV per Hf atom. Two lowest-energy patterns result in polar monoclinic structures with different transformation properties. The lowest one elastically transforms to the ferroelectric orthorhombic structure via a shear deformation, overcoming an energy barrier, which is more than twice lower than in the stoichiometric hafnia. The second-lowest structure transforms at smaller volumes to a nonpolar tetragonal one. We discuss the experimentally observed wake-up effect, fatigue, and imprint in HfO2-based ferroelectrics in terms of different local ordering of oxygen-vacancy extended defects, which favor specific crystallographic phases.
LB  - PUB:(DE-HGF)16
C6  - 34477424
UR  - <Go to ISI:>//WOS:000686914800016
DO  - DOI:10.1103/PhysRevLett.127.087602
UR  - https://juser.fz-juelich.de/record/903349
ER  -