Frequency agile BST thin films for RF/microwave applications

Heteroepitaxial Ba 0.6 Sr 0.4 TiO 3 thin films of varying thickness (~22-270 nm) were deposited on (100) oriented LaAlO 3 single crystal substrates by pulsed laser deposition using a KrF excimer laser (λ = 248 nm). XRD and FESEM were used to determine the structural quality, while RBS was used to investigate the chemical composition and thickness. The stoichiometry was found to be ideal with a Ba:Sr ratio of 1.5. XRD omega-scans showed that all films were epitaxial with a FWHM of 0.40. Interdigitated electrodes were used to measure the capacitance and Q-factor of the films in the range of 1 GHz to 20 GHz. The films exhibited a capacitance of 0.156 - 0.463 pF at room temperature, with Q-factors in the range of 4-20, depending on frequency. The tunability of BST was also measured at microwave frequencies and found to be up to 38% at 10 GHz, for the thickest sample.