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Title: Stabilizing the ferroelectric phase in doped hafnium oxide

The ferroelectric properties and crystal structure of doped HfO{sub 2} thin films were investigated for different thicknesses, electrode materials, and annealing conditions. Metal-ferroelectric-metal capacitors containing Gd:HfO{sub 2} showed no reduction of the polarization within the studied thickness range, in contrast to hafnia films with other dopants. A qualitative model describing the influence of basic process parameters on the crystal structure of HfO{sub 2} was proposed. The influence of different structural parameters on the field cycling behavior was examined. This revealed the wake-up effect in doped HfO{sub 2} to be dominated by interface induced effects, rather than a field induced phase transition. TaN electrodes were shown to considerably enhance the stabilization of the ferroelectric phase in HfO{sub 2} compared to TiN electrodes, yielding a P{sub r} of up to 35 μC/cm{sup 2}. This effect was attributed to the interface oxidation of the electrodes during annealing, resulting in a different density of oxygen vacancies in the Gd:HfO{sub 2} films. Ab initio simulations confirmed the influence of oxygen vacancies on the phase stability of ferroelectric HfO{sub 2}.
Authors:
; ;  [1] ;  [2] ;  [2] ;  [3] ;  [2] ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [1] ;  [9]
  1. NaMLab gGmbH, Noethnitzer Str. 64, D-01187 Dresden (Germany)
  2. Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)
  3. (Japan)
  4. (NIMS), Sayo, Hyogo 679-5148 (Japan)
  5. Leibniz IFW Dresden, Helmholtzstr.20, D-01171 Dresden (Germany)
  6. Fraunhofer IPMS-CNT, Koenigsbruecker Str. 180, D-01099 Dresden (Germany)
  7. Imec, Kapeldreef 75, B-3001 Leuven (Belgium)
  8. Munich University of Applied Sciences, Loth Str. 34, D-80335 Munich (Germany)
  9. (Germany)
Publication Date:
OSTI Identifier:
22494746
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANNEALING; CAPACITORS; DOPED MATERIALS; ELECTRODES; FERROELECTRIC MATERIALS; HAFNIUM OXIDES; OXIDATION; OXYGEN; PHASE STABILITY; PHASE TRANSFORMATIONS; POLARIZATION; SIMULATION; STABILIZATION; TANTALUM NITRIDES; THIN FILMS; TITANIUM NITRIDES; VACANCIES