2008 年 33 巻 1 号 p. 65-68
In this study, we investigated the crystal structure of polycrystalline BST films deposited on the glazed-Al203 and -Al203 substrates and its electrical properties. The BST films were prepared on the Pt bottom electrode/substrates by the chemical solution deposition (CSD) method. The BST films annealed at 800°C using rapid thermal annealing (RTA) were grown in random orientation on each substrate. The grain sizes were 80 nm and the average surface roughnesses Ra were approximately 3.0 nm. The dielectric constant, tan and tunability (at 428 kV/cm) of the Pt/BST/Pt/-Al2O3 film were 476, 0.0321 and 68.6% respectively, and the Pt/BST/Pt/glazed-Al2O3 film also showed practical figures, 429, 0.0498 and 58.3% respectively. We confirmed that the tunability of the Pt/BST/Pt/glazed-Al2O3 film can be maintained at above 50% up to an environmental temperature of around 80°C. This suggests that high quality BST films to apply on tunable microwave devices can be formed on a very inexpensive glazed-Al2O3 substrate.
