Designing the thermal processing of Ba(Ti 0.8 Zr 0.2 )O 3 –(Ba 0.7 Ca 0.3 )TiO 3 thin films from an ethylene glycol-derived precursor

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Abstract
Lead-free ferroelectric 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-BCT) thin films on platinized silicon substrates are prepared by chemical solution deposition route. The solution chemistry involves ethylene glycol and ethanol as solvents for alkaline earth acetates and transition metal alkoxides, respectively. The thermal decompositions of BZT-BCT xerogel, the crystallization process of BZT-BCT thin films, and their homogeneity are investigated. In xerogel, the decomposition of the organic residues occurs between 290 °C and 514 °C, followed by the formation of carbonate groups and their decomposition between 580 °C and 775 °C. In the thin films, the sequence of drying and pyrolysis steps, and the concentration of the coating solution influence the formation of carbonate groups and their decomposition upon annealing. Extending the drying and pyrolysis times from 2 minutes to 15 minutes and lowering the concentration of the coating solution from 0.2 M to 0.1 M contribute to an easier thermal decomposition of the carbon residues. Time-of-Flight Secondary Ion Mass Spectrometry analysis reveals that upon rapid thermal annealing, the decomposition of the carbonate residues in a few 10 nm thick BZT-BCT film proceeds from top downwards, resulting in pure perovskite phase faster in the thinner films than in thicker ones. The about 100 nm thick BZT-BCT film annealed at 850 °C exhibits a columnar microstructure with a homogeneous distribution of elements across the thickness of the film.
Funding Information
  • The Slovenian Research and Innovation Agency (P2-0105)
  • The Slovenian Research and Innovation Agency (P2-0082)

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