Fabrication and characterization of tunable dielectric Ba 0.5Sr 0.5TiO 3 thin films by pulsed laser deposition

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Highly oriented Ba 0.5Sr 0.5TiO 3 (BST) perovskite thin films with different thickness ranging from 120 to 600 nm have been fabricated epitaxially on SrRuO 3 (SRO) electrode layer, and (001) LaAlO 3 single crystal as substrates. We observed a strong dependence of dielectric properties on the thickness of the BST films: with the increasing of the thickness, the dielectric loss decreases, the dielectric constant increases, and the dielectric tunability increases as well. For the 600-nm-thick BST thin film, the room-temperature values at the frequency of 1 MHz of the relative dielectric constant, ε r, and loss tangent, tan δ, of 1058 and 0.0092 under no bias, and 583 and 0.0068 under 6 V bias, respectively, were achieved. A tunability of 44.8% has been achieved with DC bias as low as 6 V. The obtained measurement data renders them very attractive for the tunable microwave device applications.