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Title: Mixed electrochemical–ferroelectric states in nanoscale ferroelectrics

Ferroelectricity on the nanoscale has been the subject of much fascination in condensed-matter physics for over half a century. In recent years, multiple reports claiming ferroelectricity in ultrathin ferroelectric films based on the formation of remnant polarization states, local electromechanical hysteresis loops, and pressure-induced switching were made. But, similar phenomena were reported for traditionally non-ferroelectric materials, creating a significant level of uncertainty in the field. We show that in nanoscale systems the ferroelectric state is fundamentally inseparable from the electrochemical state of the surface, leading to the emergence of a mixed electrochemical–ferroelectric state. We explore the nature, thermodynamics, and thickness evolution of such states, and demonstrate the experimental pathway to establish its presence. Our analysis reconciles multiple prior studies, provides guidelines for studies of ferroelectric materials on the nanoscale, and establishes the design paradigm for new generations of ferroelectric-based devices.
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [3] ;  [4] ;  [5] ;  [6] ; ORCiD logo [5] ; ORCiD logo [5] ; ORCiD logo [5] ;  [7] ; ORCiD logo [5]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science; Sookmyung Women's Univ., Seoul (Korea). Dept. of Physics
  2. National Academy of Sciences of Ukraine (NASU), Kharkov (Ukraine). Inst. of Physics
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science, Computer Science and Mathematics Division
  4. National Academy of Sciences of Ukraine (NASU), Kharkov (Ukraine). Inst. of Problems of Materials Science
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science
  6. Univ. of Lyon (France). Inst. of Nanotechnologies
  7. Univ. of Lyon (France). Inst. of Nanotechnologies; Helmholtz-Zentrum Berlin for Materials and Energy, Berlin (Germany)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Nature Physics
Additional Journal Information:
Journal Volume: 13; Journal Issue: 8; Journal ID: ISSN 1745-2473
Publisher:
Nature Publishing Group (NPG)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; electronic properties and materials; ferroelectronics and multiferroics; nanoscale materials; surfaces, interfaces and thin films
OSTI Identifier:
1407724