Anisotropic electric field effect in YBa2Cu3O7−x thin films grown on (110) SrTiO3 substrates

The effect of in-plane strain on the nonlinear dielectric properties of SrTiO3 epitaxial thin films is calculated using density-functional theory within the local-density approximation. Motivated by recent experiments, the structure, zone-center phonons, and dielectric properties with and without an external electric field are evaluated for several misfit strains within ±3% of the calculated cubic lattice parameter. In these calculations, the in-plane lattice parameters are fixed, and all remaining structural parameters are permitted to relax. The presence of an external bias is treated approximately by applying a force to each ion proportional to the electric field. After obtaining zero-field ground state structures for various strains, the zone-center phonon frequencies and Born effective charges are computed, yielding the zero-field dielectric response. The dielectric response at finite electric field bias is obtained by computing the field dependence of the structure and polarization using an approximate technique. The results are compared with recent experiments and a previous phenomenological theory. The tunability is found to be strongly dependent on the in-plane lattice parameter, showing markedly different behavior for tensile and compressive strains. Our results are expected to be of use for isolating the role of strain in the tunability of real ultrathin epitaxial films.

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“…as has been used previously in the literature. 47,48 Making the approximation ǫ ≫ 1 so that ǫ ≃ 4πχ, we can write…”

Section: Dielectric Properties and Tunabilitymentioning

confidence: 99%

Tunability of the dielectric response of epitaxially strainedSrTiO3from first principles

et al. 2005

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“…3 Another appealing feature of STO is the electric field dependence of the dielectric constant which offers the opportunity for the development of various microwave devices such as microstrip line phase shifters, tunable filters, and high Q resonators. [4][5][6][7] Furthermore, due to the structural similarity to other technically important perovskite materials showing high temperature superconductivity or colossal magnetoresistance, STO is a very important building block for the design of new low temperature microelectronic devices, e.g., as a barrier material for quasiparticle 8 and spin-polarized quasiparticle injection devices, 9 superconducting field effect transistors, 10 and spin valves for high sensitivity magnetic field sensors. 11,12 For many devices high quality STO thin films having a dielectric constant and resistivity comparable to STO single crystals are required.…”

Section: Introductionmentioning

confidence: 99%

Structural properties of slightly off-stoichiometric homoepitaxial SrTixO3−δ thin films

Fuchs

Adam

Schweiß

et al. 2000

Journal of Applied Physics

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Ti-deficient SrTixO3−δ films, x<1, were grown on 〈100〉 oriented SrTiO3 single crystal substrates by radio frequency magnetron sputtering from stoichiometric targets. The Ti-deficiency was adjusted by the sputtering gas pressure. The Ti/Sr cation ratio, x, was determined by Rutherford backscattering and energy dispersive x-ray analysis in a scanning electron microscope. To obtain information on the Ti/O ratio, x-ray absorption spectroscopy was carried out as well. We investigated SrTixO3−δ films with x=0.98, 0.95, and 0.89. The epitaxial growth and lattice imperfections were characterized by x-ray diffraction, electron diffraction, and high resolution transmission electron microscopy. The films crystallized in a tetragonal structure with a maximum mosaic spread of about 0.1°. The c axis was oriented perpendicular to the substrate surface where the c-lattice parameter was increasing with decreasing x. For x>0.89, the Ti deficiency was primarily compensated by a change of the site occupation on the cation sublattices in combination with oxygen vacancies, i.e., the formation of SrTi and VO point defects, whereas for x<0.95 the intergrowth of homologs series of the Ruddlesden–Popper phases, Srn+1TinO3n+1, was observed. The dielectric properties of the films are briefly discussed in terms of (SrTiVO) defect complexes.

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“…In addition, STO thin films show very good insulating properties, with a breakdown V as high as 10 5 V/cm. Such feature makes this material suitable as artificial barrier for high-T superconductor quasiparticles injection devices as well as for capacitive charging in superconducting field effect transistors [1]. In addition, the non liner dependence of the dielectric constant (ε), on the electric field (E), is important for the development of tunable microwave devices [2].…”

Section: Introductionmentioning

confidence: 99%

Study of SrTiO3 thin films grown by sputtering technique for tunnel barriers in quasiparticle injection contacts

2009

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Anisotropic electric field effect in YBa2Cu3O7−x thin films grown on (110) SrTiO3 substrates

Cited by 9 publications

References 22 publications

Tunability of the dielectric response of epitaxially strainedSrTiO3from first principles

Tunability of the dielectric response of epitaxially strainedSrTiO3from first principles

Structural properties of slightly off-stoichiometric homoepitaxial SrTixO3−δ thin films

Study of SrTiO3 thin films grown by sputtering technique for tunnel barriers in quasiparticle injection contacts

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