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Title: Cation–Eutectic Transition via Sublattice Melting in CuInP 2S 6/In 4/3P 2S 6 van der Waals Layered Crystals

Single crystals of the van der Waals layered ferrielectric material CuInP 2S 6 spontaneously phase separate when synthesized with Cu deficiency. In this paper, we identify a route to form and tune intralayer heterostructures between the corresponding ferrielectric (CuInP 2S 6) and paraelectric (In 4/3P 2S 6) phases through control of chemical phase separation. We conclusively demonstrate that Cu-deficient Cu 1–xIn 1+x/3P 2S 6 forms a single phase at high temperature. We also identify the mechanism by which the phase separation proceeds upon cooling. Above 500 K both Cu + and In 3+ become mobile, while P 2S 6 4– anions maintain their structure. We therefore propose that this transition can be understood as eutectic melting on the cation sublattice. Such a model suggests that the transition temperature for the melting process is relatively low because it requires only a partial reorganization of the crystal lattice. As a result, varying the cooling rate through the phase transition controls the lateral extent of chemical domains over several decades in size. At the fastest cooling rate, the dimensional confinement of the ferrielectric CuInP 2S 6 phase to nanoscale dimensions suppresses ferrielectric ordering due to the intrinsic ferroelectric size effect. Finally, intralayer heterostructuresmore » can be formed, destroyed, and re-formed by thermal cycling, thus enabling the possibility of finely tuned ferroic structures that can potentially be optimized for specific device architectures.« less
ORCiD logo [1] ; ORCiD logo [2] ;  [2] ;  [3] ;  [3] ;  [4] ;  [3] ;  [2] ;  [3] ;  [5] ;  [3] ; ORCiD logo [3] ;  [2] ;  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Air Force Research Lab. (AFRL), Wright-Patterson AFB, OH (United States). Aerospace Systems Directorate; UES Inc., Beavercreek, OH (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  4. Argonne National Lab. (ANL), Argonne, IL (United States). X-Ray Science Division
  5. Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemical and Biomolecular Engineering
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-06CH11357; 14RQ08COR
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 11; Journal Issue: 7; Journal ID: ISSN 1936-0851
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); US Air Force Office of Scientific Research (AFOSR); National Research Council (United States)
Contributing Orgs:
UES Inc., Beavercreek, OH (United States); Georgia Inst. of Technology, Atlanta, GA (United States)
Country of Publication:
United States
36 MATERIALS SCIENCE; 2D ferrielectric; 2D heterostructures; chalcogenides; sublattice melting; transition metal thiophosphate
OSTI Identifier: