TY  - JOUR
AU  - Schie, Marcel
AU  - Menzel, Stephan
AU  - Robertson, John
AU  - Waser, R.
AU  - De Souza, Roger A.
TI  - Field-enhanced route to generating anti-Frenkel pairs in HfO 2
JO  - Physical review materials
VL  - 2
IS  - 3
SN  - 2475-9953
CY  - College Park, MD
PB  - APS
M1  - FZJ-2019-00882
SP  - 035002
PY  - 2018
AB  - The generation of anti-Frenkel pairs (oxygen vacancies and oxygen interstitials) in monoclinic and cubic HfO2 under an applied electric field is examined. A thermodynamic model is used to derive an expression for the critical field strength required to generate an anti-Frenkel pair. The critical field strength of EcraF∼101GVm−1 obtained for HfO2 exceeds substantially the field strengths routinely employed in the forming and switching operations of resistive switching HfO2 devices, suggesting that field-enhanced defect generation is negligible. Atomistic simulations with molecular static (MS) and molecular dynamic (MD) approaches support this finding. The MS calculations indicated a high formation energy of ΔEaF≈8eV for the infinitely separated anti-Frenkel pair, and only a decrease to ΔEaF≈6eV for the adjacent anti-Frenkel pair. The MD simulations showed no defect generation in either phase for E<3GVm−1, and only sporadic defect generation in the monoclinic phase (at E=3GVm−1) with fast (trec<4ps) recombination. At even higher E but below EcraF both monoclinic and cubic structures became unstable as a result of field-induced deformation of the ionic potential wells. Further MD investigations starting with preexisting anti-Frenkel pairs revealed recombination of all pairs within trec<1ps, even for the case of neutral vacancies and charged interstitials, for which formally there is no electrostatic attraction between the defects. In conclusion, we find no physically reasonable route to generating point-defects in HfO2 by an applied field.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000468106600001
DO  - DOI:10.1103/PhysRevMaterials.2.035002
UR  - https://juser.fz-juelich.de/record/860096
ER  -