“…Ba 1− x Sr x TiO 3 (BSTO) thin film is an important material because of its excellent properties, such as optical properties, resistive switching, dielectric properties, etc. Recently, it has been considered to be an important candidate material for various tunable microwave devices such as microwave tunable phase shifters, filters, oscillators, and antennas because of its high dielectric constant, relatively low dielectric loss tangent, and high tunability .…”