Magnetron sputtered Ba(1-x)SrxTiO3 thin films

Thin films of Ba_(1-x)Sr_xTiO₃ (BST) have been deposited by inverted cylindrical magnetron (ICM) and off-axis cosputtering at high sputter gas pressures. The ICM technique uses a single BST target and the off-axis technique uses BaTiO₃ and SrTiO₃ targets. Films were deposited at gas pressures ranging from 6.7 to 53 Pa and at substrate temperatures from 550 to 800°C. By combining high gas pressures with unconventional geometries the negative ion bombardment of the growing film, characteristic of oxide film growth, has been minimized. This results in well oxygenated stoichiometric BST films. The surface morphology and grain structure were investigated and related to the measured microwave properties. The films had lattice parameters dependent on deposition conditions. Grain sizes were approximately 0.25 μm for most films after an oxygen anneal at 780°C. Both techniques have yielded films having Q > 1000 with tuning of nearly 7%