Microwave Dielectric Properties of (111) Oriented Ferroelectric (Ba_{1 − x}Sr_x)TiO₃ Thin Films

Abstract

Epitaxial (111) oriented ferroelectric (Ba_{1 − x}Sr_x)TiO₃ (BST) films were deposited on MgO (111) single crystals using pulsed laser deposition. Structural properties of BST films were investigated using X-ray diffractometer. The dielectric properties of BST films were investigated under the dc bias field of 0–40 V using interdigital capacitors (IDT) fabricated by photolithography and etching process. The small signal dielectric properties of BST films were calculated by modified conformal mapping both the measured data using an impedance gain/phase analyzer and the reflection coefficient data measured using a HP 8510C vector network analyzer in 0.05–10 GHz at room temperature. The IDT capacitor based on (111) oriented BST film exhibits about 40% of capacitance change with an dc bias of 40 V which value is somewhat smaller than that of the IDT device based on (001) oriented BST film. But the dielectric quality factor value is about twice that of the device based on (001) oriented BST film.

Keywords:

• (Ba_{1 − x}Sr_x)TiO₃ (BST) films
• interdigital capacitor
• microwave properties
• s-parameter
• dielectric quality factor