Microwave dielectric properties of BaTi₄O₉ thin film

BaTi₄O₉ thin films have been prepared by RF magnetron sputtering on the Pt/Ti/SiO₂/Si substrates and the dielectric properties of the BaTi₄O₉ film have been investigated at microwave frequency range. The homogeneous BaTi₄O₉ thin film was obtained when the film was grown at 550 °C and rapid thermal annealed (RTA) at 900 °C for 3 min. The circular-patch capacitor (CPC) was used to measure the microwave dielectric properties of the film. The dielectric constant (ε_r) and the dielectric loss (tan δ) were successfully measured up to 6 GHz. The ε_r of the BaTi₄O₉ thin film slightly increased with the increase of the film thickness. However, the tan δ decreased with increasing the thickness of the film. The ε_r of BaTi₄O₉ thin film was similar to that of the BaTi₄O₉ ceramics, which is about 36-39. The tan δ of the film with 460 nm thickness was very low approximately, 0.0001 at 1-3 GHz. Since BaTi₄O₉ film has a high ε_r and a low tan δ, the BaTi₄ O₉ film can be used as the microwave devices.