Crystallization process of Sr0.7Bi2.3Ta2O9 thin films with different crystal orientation prepared by chemical liquid deposition using alkoxide precursor

Ichiro Koiwa, Takao Kanehara, Juro Mita, Tetsuya Osaka, Sachiko Ono, Akira Sakakibara, Tomonori Seki

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The crystallization process of Sr0.7Bi2.3Ta2O9 (SBT) ferroelectric thin films with different crystal orientations formed by chemical liquid deposition using an alkoxide precursor was investigated. One film showed strong c-axis orientation (a-type film), while another shows scarcely any c-axis orientation (b-type film). We report that the crystallization process was the same even when crystal orientation differed. Thin films first change from amorphous to fluorite fine grains; the fiuorite grains then change to bismuth layer-structure grains. The different orientation of the SBT films is not caused by different crystallization process. Both SBT films with different crystal orientations consist of fine fluorite grains after 650°C heat-treatment. Their leakage current density characteristics differ, however. The leakage current density of the a-type film was independent of the electric field, and showed a low value of 10-8A/cm2. The leakage current density of the b-type film, however, was dependent on the electric field, and increased continuously with the increasing electric field. After 700°C heat-treatment, both films consist of large grains with bismuth layer-structure and fine fiuorite grains. The matrix of both films contains large grains with bismuth layer-structure that determines the leakage current density characteristics. Since the fiuorite grain size after a 700°C heat-treatment is the same as that after 650°C heat-treatment, nucleation is predominant at the structural phase boundary from amorphous to fluorite. The bismuth layer-structure grains are large and single-crystal grains after both a 700 and 800°C heattreatment. Increased grain size predominates at the structural phase boundary from fluorite to bismuth layer-structure grains. Clearly, ferroelectric SBT films with bismuth layer-structure are crystallized in two steps, each having a different predominant crystal growth mechanism.

Original languageEnglish
Pages (from-to)552-558
Number of pages7
JournalIEICE Transactions on Electronics
VolumeE81-C
Issue number4
Publication statusPublished - 1998 Jan 1
Externally publishedYes

Keywords

  • Alkoxide precursor
  • Crystallization process
  • Ferroelectric memory
  • Srbitao thin film

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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