title: The stabilization of a single domain in free-standing ferroelectric nanocrystals.
abstract: High resolution electron microscopy, electron diffraction and electron holography were used to study individual free-standing ∼ 30 nm barium titanate nanocrystals. Large unidirectional variations in the tetragonal distortion were mapped across the smaller nanocrystals, peaking to anomalously large values of up to 4% at the centers of the nanocrystals. This indicated that the nanocrystals consist of highly strained single ferroelectric domains. Simulations using an effective Hamiltonian for modeling a nanocrystal under a small depolarizing field and negative pressure qualitatively confirm this picture. These simulations, along with the development of a phenomenological model, show that the tetragonal distortion variation is a combined effect of: (i) electrostrictive coupling between the spontaneous polarization and strain inside the nanocrystal, and (ii) a surface-induced effective stress existing inside the nanodot. As a result, a 'strain skin layer', having a smaller tetragonal distortion relative to the core of the nanocrystal, is created.
authors.affiliation: Department of Chemical Physics, School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel-Aviv University, Tel-Aviv 69978, Israel.
authors.forename: Daniel
authors.initials: D
authors.lastname: Szwarcman
authors.forename: S
authors.initials: S
authors.lastname: Prosandeev
authors.forename: Lydie
authors.initials: L
authors.lastname: Louis
authors.forename: Shlomo
authors.initials: S
authors.lastname: Berger
authors.forename: Yuri
authors.initials: Y
authors.lastname: Rosenberg
authors.forename: Yossi
authors.initials: Y
authors.lastname: Lereah
authors.forename: L
authors.initials: L
authors.lastname: Bellaiche
authors.forename: Gil
authors.initials: G
authors.lastname: Markovich
mesh_terms: D017609:Barium Compounds / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D060526:Magnetic Fields; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D014025:Titanium / Q000737:chemistry*
chemical_list: D017609:Barium Compounds; C024547:barium titanate(IV); D014025:Titanium