High quality Ba_xSr_1-xTiO₃ films grown by mocld and novel ferroelectric/ferrite structures for dual-tuning microwave devices

Abstract

Excellent single crystal Ba_xSr_1-xTiO₃ (BST) films were grown on LaAlO₃ substrates using the metal-organic chemical liquid deposition (MOCLD) method. Very low losses (tanδ ∽0.002-0.008) were measured from these films at 400 KHz. Biaxially oriented BST films were successfully grown on polycrystalline YIG substrates using both MOCLD and pulsed laser deposition methods with biaxially oriented MgO and YSZ buffer layers. The dielectric losses of the films range from 0.005 to 0.015 while 25% of dielectric constant change was observed with 40V bias voltage up to 10 MHz. Both the dissipation and dielectric constant of the films remained nearly constants over a wide temperature range (77 K to 380 K). A dual-tuning microwave coplanar phase shifter using a BST film grown on a MgO buffered polycrystalline YIG substrate was fabricated. A significant phase shift was observed in GHz frequency range when an electric bias or a magnetic field was applied to the device.

Key Words:

• ferroelectric
• ferrite
• dual-tuning
• microwave
• buffer layer