Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices

TL;DR

This study demonstrates that doping Ba0.5Sr0.5TiO3 thin films with Al2O3 reduces dielectric loss and enhances the figure of merit, making them suitable for tunable microwave devices.

Contribution

It introduces Al2O3 doping in BST thin films as a method to improve dielectric properties for microwave applications.

Findings

Al2O3 doping reduces dielectric constant and loss.

Doped films show increased figure of merit.

Surface roughness and grain size are affected by Al2O3 content.

Abstract

Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increased with the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD result indicating the grain size of the Al2O3-BST films reduced with the increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST films with a home-made non-destructive dual resonator method at frequency ~ 7.7 GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the dielectric constant, dielectric loss and tunability compare to pure BST thin film. Our result shows the figure of merit (K), used to compare the films with varied dielectric properties, increased with the Al2O3 content. Therefore Al2O3-BST films show the potential to be exploited in tunable microwave devices.