Effect of crystallinity on microwave tunability of pulsed laser deposited Ba < inf > 0.5 < /inf > Sr < inf > 0.5 < /inf > TiO < inf > 3 < /inf > thin films

Abstract

Barium Strontium Titanate (Ba0.5Sr0.5TiO3) thin films on (100) oriented MgO substrates were deposited by Pulsed Laser Deposition (PLD) technique. The deposition temperature of 750 °C is kept constant and the oxygen working pressure is varied from ~ 1 × 10− 1 mbar to 1 × 10− 4 mbar. The X-ray diffraction pattern shows that higher oxygen working pressure deposited films are partially crystalline. The lower oxygen working pressure (1 × 10− 4 mbar) deposited films showed improved crystallinity. The crystallinity is further increased with a particular orientation as the laser fluence increased from 1.4 J/cm2 to 2 J/cm2.The microwave dielectric properties of these films were measured using Inter Digitated Capacitor (IDC) test structure. It is found that the maximum tunability (in IDC configuration) of 16.5% at 1GHz is obtained for oxygen working pressure and high fluence (1 × 10− 4 mbar and 2 J/cm2) deposited films, whereas the other films tunabilities are in the range of 1–2% only. These studies also help us to explore the correlation between structure and microwave dielectric properties. Hence, in the present study the 1 × 10− 4 mbar and 2 J/cm2 deposition conditions are found to be more helpful in unleashing conditions that lead to better tunability in Ba0.5Sr0.5TiO3 films.