Nonlinear dielectric properties of Ba(Ti,Zr)O3 thin films for tunable microwave device applications

Nano-structured barium zirconate titanate Ba(Ti_1-xZr_x)O₃ (BTZ, x=0.20, 0.25,0.30 and 0.35, abbreviated as BTZ20, BTZ25, BTZ30, and BTZ35, respectively) thin films on Pt/Ti/SiO₂/Si(100) substrates have been prepared by pulse laser deposition (PLD) using a KrF Excimer Laser, lambda Physik Complex (λ= 248 nm, 650 mJ, 25 ns). The targets are BTZ20, BTZ25, BTZ30 and BTZ35. The films were deposited at a laser repetition rate of 10 Hz and pulse laser energy of 300 mJ. The deposition rate was 20 nm/min. The oxygen pressure was an important factor and was kept 200 mTorr. Finally, the thin films were crystallized in situ at 650°C in 400 mTorr of oxygen for 20 min and cooled down slowly to room temperature. The thin films were characterized using XRD and SEM. Dielectric measurements revealed that the thin films a relaxor behavior and have a diffuse phase transition when the Zr content of x increased from 0.20 to 0.35. The tunability decreased and figure of merit increased when the Zr content of x increased from 0.20 to 0.35, respectively for BTZ the thin films. Both of BTZ thin films with Zr content of 0.30 and 0.35 have low dielectric constant and high figure of merit. Therefore, the BTZ thin film is an attractive candidate for microwave tunable device applications.