Dielectric Properties of Large Area Processed Nanostructured Barium Strontium Titanate Thin-films

Nanostructured Ba0.6Sr0.4TiO₃ (BST) thin-films with large dielectric tunability as high as 4:1 were obtained using a large area pulsed laser deposition process, with low loss-tangents below 0.01 at zero-bias and 10 GHz. This paper summarizes experimental results obtained on large area processed BST thin films. The BST thin films were characterized using a varactor shunt switch device. The BST thin films with an average grain size of 60 nm exhibited large dielectric tunability, the relative dielectric permittivity at zero bias of 1000 tuned to 250 at 8 V dc bias. The loss-tangent of the BST films was 0.006 at zero bias, and reduced to 0.003 at 10 V, at 10 GHz. The leakage current through the BST film was below 1 nA up to 5 V dc bias. These results confirm that large area processed BST thin films are ready for commercial applications such as for frequency and phase agile circuits.