Reactive coevaporation of SrTiO3 thin films for tunable microwave devices

We have successfully grown SrTiO3 films on LaAlO3 and MgO substrates up to 2" in diameter using the deposition technique of reactive coevaporation. We have explored a wide range of deposition temperatures, oxygen pocket pressures, and compositions in order to determine the optimal growth process window. X-ray diffraction analyses indicate that the process window for growth on MgO substrates is narrower than for LaAlO3 substrates. Dielectric property measurements show that samples near stoichiometry have higher tunability, but their peak loss tangents are also high (similar to0.02). The slightly Sr-poor samples (46-48 at.%) show a reduced loss tangent (<0.01) while maintaining an acceptable tunability (similar to50%) at an average electric field of 1.7 V/mum.