Relaxor ferroelectricity in strained epitaxial SrTiO3 thin films on DyScO3 substrates

Abstract

Effect of stoichiometry on the dielectric properties and soft mode behavior of strained epitaxial SrTiO3 thin films on DyScO3 substrates Appl. Phys. Lett. 102, 082905 (2013); 10.1063/1.4793649 The effect of the top electrode interface on the hysteretic behavior of epitaxial ferroelectric Pb(Zr,Ti)O3 thin films with bottom SrRuO3 electrode J. Appl. Phys. 112, 064116 (2012); 10.1063/1.4754318 Dielectric and ferroelectric properties of strain-relieved epitaxial lead-free KNN-LT-LS ferroelectric thin films on Sr Ti O 3 substratesThe ferroelectric properties of 500 Å thick strained, epitaxial SrTiO 3 films grown on DyScO 3 substrates by reactive molecular-beam epitaxy are reported. Despite the near 1% biaxial tensile strain, the x-ray rocking curve full widths at half maximum in are as narrow as 7 arc sec ͑0.002°͒. The films show a frequency-dependent permittivity maximum near 250 K that is well fit by the Vogel-Fulcher equation. A clear polarization hysteresis is observed below the permittivity maximum, with an in-plane remanent polarization of 10 C/cm 2 at 77 K. The high T max is consistent with the biaxial tensile strain state, while the superimposed relaxor behavior is likely due to defects.

Evidence for Strain-Induced Ferroelectric Order in Epitaxial Thin-FilmKTaO3

“…The relaxorlike properties evidenced in epitaxial films of ðBa; SrÞTiO 3 [13] indicate a presence of the short-range-order region in the phase diagram for this FE, too. Similar short-range order found in epitaxial films grown by different methods and in different laboratories [9,12,13] suggests its fundamental origin, not related to technological imperfections. Studies of dynamic effects might give a clue to understanding this origin [12,28].…”

“…1). This differs from the relaxorlike state in epitaxial films of quantum paraelectric SrTiO 3 with the in-plane tensile strain s % 1% [9], also well beyond the theoretical paraelectric gap [4,5]. To demonstrate that strain-induced FE order is characteristic not only for KTO or compressive strain, we show here the temperature dependence of refraction index nðTÞ measured in epitaxial film of SrTiO 3 with the in-plane tensile strain s ¼ 2:1%.…”

“…However, in epitaxial films of SrTiO 3 , in contrast to the predicted long-range FE order, relaxorlike behavior has been experimentally proved [9]. In relaxor ferroelectrics, or relaxors, long-range FE polarization order and FE domains are absent.…”

“…In contrast to FEs, in relaxors with shortrange order of polarization, a peak in the temperature dependence of the dielectric permittivity is not associated with the paraelectric-to-FE phase transition. In SrTiO 3 films, the dielectric peak [5] is of relaxor nature [9]. Importantly, in epitaxial films of perovskite-type relaxors, strain has been found to enhance relaxor features, but not to induce the FE state [11].…”

Magnetic-field-induced spontaneous superlattice formation via spinodal decomposition in epitaxial strontium titanate thin films

“…In the literature, strain-induced ferroelectricity of SrTiO 3 thin films was reported mainly along the inplane direction. 21,22,42 Very few reports describe phenomena along the out-of-plane direction. [43][44][45] The out-of-plane ferroelectricity reported by Warusawithana et al 43 is limited in terms of thickness (less than 10 ML) and that reported by Kim et al 44,45 originates from vacancies.…”