NONLINEAR DIELECTRIC PROPERTIES OF (Ba,Sr)TiO₃ AND Ba(Zr,Ti)O₃ THIN FILMS FOR TUNABLE MICROWAVE DEVICE APPLICATIONS

ABSTRACT

Barium strontium titanate (Ba_0.50Sr_0.50)TiO₃ (BST), and barium zirconate titanate Ba(Zr_0.35Ti_0.65)O₃ (BZT) thin films on Pt-coated silicon substrates have been prepared by pulse laser deposition. The highly (100)-oriented BST and BZT thin films with nano-sized grains of 15∼25 nm have been characterized by X-ray diffraction, atomic force microscopy and impedance measurements. The dielectric constant and dissipation factor of BST and BZT thin films were 822 and 0.025, 416 and 0.015 at 1 MHz, respectively. The dielectric constant of BST and BZT thin films changes significantly with applied dc bias field and has high tunabilities and figures of merit of 63% and 42, 67% and 45, respectively under an applied field of 250 kV/cm.

Keywords:

• Pulsed laser deposition
• dielectric properties
• BZT thin films
• electric field
• tunability

ACKNOWLEDGMENTS

This work is supported by the Natural Science Foundation of Guangdong, China (Grant No. 05001825), the Postdoctoral Fellowship Scheme and the Centre for Smart Materials of the Hong Kong Polytechnic University.