title: Ferroelectricity in strain-free SrTiO3 thin films.
abstract: Biaxial strain is known to induce ferroelectricity in thin films of nominally nonferroelectric materials such as SrTiO3. By a direct comparison of the strained and strain-free SrTiO3 films using dielectric, ferroelectric, Raman, nonlinear optical and nanoscale piezoelectric property measurements, we conclude that all SrTiO3 films and bulk crystals are relaxor ferroelectrics, and the role of strain is to stabilize longer-range correlation of preexisting nanopolar regions, likely originating from minute amounts of unintentional Sr deficiency in nominally stoichiometric samples. These findings highlight the sensitive role of stoichiometry when exploring strain and epitaxy-induced electronic phenomena in oxide films, heterostructures, and interfaces.
authors.affiliation: Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: H W
authors.initials: HW
authors.lastname: Jang
authors.forename: A
authors.initials: A
authors.lastname: Kumar
authors.forename: S
authors.initials: S
authors.lastname: Denev
authors.forename: M D
authors.initials: MD
authors.lastname: Biegalski
authors.forename: P
authors.initials: P
authors.lastname: Maksymovych
authors.forename: C W
authors.initials: CW
authors.lastname: Bark
authors.forename: C T
authors.initials: CT
authors.lastname: Nelson
authors.forename: C M
authors.initials: CM
authors.lastname: Folkman
authors.forename: S H
authors.initials: SH
authors.lastname: Baek
authors.forename: N
authors.initials: N
authors.lastname: Balke
authors.forename: C M
authors.initials: CM
authors.lastname: Brooks
authors.forename: D A
authors.initials: DA
authors.lastname: Tenne
authors.forename: D G
authors.initials: DG
authors.lastname: Schlom
authors.forename: L Q
authors.initials: LQ
authors.lastname: Chen
authors.forename: X Q
authors.initials: XQ
authors.lastname: Pan
authors.forename: S V
authors.initials: SV
authors.lastname: Kalinin
authors.forename: V
authors.initials: V
authors.lastname: Gopalan
authors.forename: C B
authors.initials: CB
authors.lastname: Eom