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Title: Size-effect in layered ferrielectric CuInP2S6

In this paper, we report on polarization switching properties of thin flakes of van der Waals ferrielectric CuInP2S6. We observe mesoscale polarization domains, ferroelectric switching, and the Curie temperature above 299 K down to a thickness of ~50 nm. However, the electromechanical response is progressively suppressed below 50 nm, and vanishes at room temperature at a thickness of ~10 nm. Though larger than a single layer, 10 nm is still a very small value compared to the expectations for an intrinsic ferroelectric semiconductor. We therefore propose a model for a doped surface layer that screens spontaneous polarization in this material. The charges in the screening layer may also participate in secondary chemical reactions, which may explain domain pinning observed in thermal cycling of the flakes above the Curie temperature. At the same time, ferroelectric switching is intertwined with ionic diffusion, resulting in erratic and damaging switching at room temperature. Finally, owing to much stronger temperature dependence of ionic diffusion, the two phenomena can be decoupled allowing more reliable switching to be obtained at low temperatures.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [1] ;  [4] ;  [2] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). The Center for Nanophase Materials Sciences
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  3. National Academy of Sciences of Ukraine (NASU), Kiev (Ukraine). Inst. for Problems of Materials Science
  4. National Academy of Sciences of Ukraine (NASU), Kiev (Ukraine). Inst. of Physics
Publication Date:
OSTI Identifier:
1361286
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 109; Journal Issue: 17; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
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); USDOE Laboratory Directed Research and Development (LDRD) Program
Contributing Orgs:
National Academy of Sciences of Ukraine (NASU), Kiev (Ukraine)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Polarization; Ferroelectric materials; Ferroelectric switching; Ferroelectric phase transitions; Atomic force microscopy