The electric field dependence of the dielectric constant of ferroelect
ric and related materials can be used to fabricate voltage tunable fil
ters for microwave applications. In this study, the growth, structure,
and dielectric properties of sputter deposited thin films will be dis
cussed. In particular, SrTiO3 thin films were deposited onto (100)(pc)
LaAlO3 and r-cut sapphire substrates using RF magnetron sputtering at
elevated temperatures. The films deposited on LaAlO3 were highly (00l
) oriented possessing a cube-on-cube heteroepitaxial structure, while
the films deposited directly on sapphire were polycrystalline. We have
studied the influence of deposition conditions and post deposition an
nealing on the crystal quality, microstructure, and electrical propert
ies. We find that post deposition annealing can significantly improve
the tunability of heteroepitaxial films. The magnitude and tunability
of the dielectric constant will be correlated with film crystalline qu
ality and microstructure.