Epitaxial Growth of Nano-Crystalline Potassium Tantalate Thin Film by Hydrothermal Electrodeposition

Abstract

Hydrothermal electrodeposition is novel solution process and has successfully prepared the epitaxial perovskite-type oxide thin films of BaTiO₃, PbTiO₃ and Pb(Zr_xTi_1-x)O₃ on single crystal SrTiO₃ substrate with La_0.7Sr_0.3MnO₃ buffer layer (LSMO/STO). KTaO₃ is one of ferroelectric materials and KTaO₃ thin film was tried to be synthesized by hydrothermal electrodeposition at 80-100^oC in this study. Ta₂O₅ powder was put into 18.5 M KOH and LSMO/STO was suspended in this solution. 1 V was applied between LSMO/STO and Pt counter electrodes. After 24 h, KTaO₃ thin film was deposited on LSMO/STO substrate. The only KTaO₃ (00l) peaks were observed in XRD, suggesting c-axis orientation. The KTaO₃ (002) peak appeared at 45.43-45.62^o and shifted to lower degree with increasing film thickness. The film growth started from the deposition of fine and cubic particles (ca. 20 nm). Then the fine particles were united to form larger and flat crystallites (ca. 200 nm).