Mechanical strain engineering of dielectric tunability in polycrystalline SrTiO3 thin films


Optimizing performance using low cost scalable processing and substrates is critical if functional oxide thin films are to achieve commercialisation. Here, we present a comprehensive investigation of the role of low cost Al2O3, SrTiO3, and MgO substrates in the structure, microstructure and electrical properties of SrTiO3 (ST) thin films, deposited by sol-gel processing. We demonstrate that the dielectric properties of polycrystalline ST films depend on the strain/stress induced by the substrates. ST films deposited on Al2O3/Pt substrates under a high tensile stress possess the smallest grain size and present the lowest value of the relative permittivity, er, with the lowest dielectric tunability. In contrast, ST films deposited on MgO/Pt substrates, under the highest compressive stress, have the highest value of er, tunability and polarization. It is thus demonstrated that for polycrystalline ST films the relative permittivity and dielectric tunability may be optimised through an induced compressive stress state.




Materials Science; Physics


Tkach, A; Okhay, O; Reaney, IM; Vilarinho, PM

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This work was funded by FEDER funds via Programa Operacional Factores de Competitividade - COMPETE and National funds via FCT (Fundacao para a Ciencia e Tecnologia) within the Project CICECO - FCOMP-01-0124-FEDER-037271 (FCT PEst-C/CTM/LA0011/2013) as well as within the FCT independent researcher grant IF/00602/2013. I. M. Reaney acknowledges the support of the Engineering and Physical Sciences Research Council grant, EP/L017563/1. M. R. Soares is acknowledged for XRD analysis.

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