Fabrication and characterization of (1−x)SrBi2Ta2O9–xBi3TaTiO9 layered structure solid solution thin films for ferroelectric random access memory (FRAM) applications |
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Authors: | S O Ryu S Tirumala P C Joshi S B Desu |
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Affiliation: | Department of Materials Science and Engineering, 213 Holden Hall, Virginia Tech, Blacksburg, VA 24061-0237, USA |
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Abstract: | We report on the properties of (1?x)SrBi2Ta2O9–xBi3TaTiO9 solid solution thin films for ferroelectric non-volatile memory applications. The solid solution thin films fabricated by modified metalorganic solution deposition technique showed much improved properties compared to SrBi2Ta2O9. A pyrochlore free crystalline phase was obtained at a low annealing temperature of 600°C and grain size was found to be considerably increased for the solid solution compositions. The film properties were found to be strongly dependent on the composition and annealing temperatures. The measured dielectric constant of the solid solution thin films was in the range 180–225 for films with 10–50% of Bi3TaTiO9 content in the solid solution. Ferroelectric properties of (1?x)SrBi2Ta2O9–xBi3TaTiO9 thin films were significantly improved compared to SrBi2Ta2O9. For example, the observed remanent polarization (2Pr) and coercive field (Ec) values for films with 0.7SrBi2Ta2O9–0.3Bi3TaTiO9 composition, annealed at 650°C, were 12.4 μC/cm2 and 80 kV/cm, respectively. The solid solution thin films showed less than 5% decay of the polarization charge after 1010 switching cycles and good memory retention characteristics after about 106 s of memory retention. The improved microstructural and ferroelectric properties of (1?x)SrBi2Ta2O9–xBi3TaTiO9 thin films compared to SrBi2Ta2O9, especially at lower annealing temperatures, suggest their suitability for high density FRAM applications. |
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Keywords: | Bismuth Deposition process Electrical properties and measurements Ferroelectric properties |
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