Effect of annealing on the crystal structure and dielectric properties of Ba0.6Sr0.4TiO3 thick films

Ba0.6Sr0.4TiO3 (BST) films with different thickness were grown on (0 0 1) MgO substrates by pulsed laser deposition. Effects of thickness and post-deposition annealing on the crystal structure and dielectric properties of BST films are investigated. Enhancement of the crystal structure through post-deposition annealing is analyzed from the viewpoint of energy minimization principle of stable state. The best dielectric properties are obtained for the 500-nm-thick BST film with post-deposition annealing at 1000 °C in flowing O2 atmosphere. Based on the high-quality BST film, a distributed microwave phase shifter was fabricated, and promising high-frequency device performance is achieved.