Sputter-deposited thin films and multilayers of YBa₂Cu₃O_7-δ (YBCO) and SrTi0₃ (STO) have been grown and studied. Microstructure in general, and formation of secondary phases, in particular, have been studied in relation to growth conditions. The main characterization techniques used have been x-ray diffraction (XRD) to identify phases and to obtain orientational relationships, scanning electron microscopy (SEM) to study surface morphology, transmission electron microscopy (TEM) for micro-structural characterization, and energy-dispersive x-ray spectroscopy (EDS) for chemical characterization.

The influence of the composition of the sputtering target as well as process gas composition on the phase formation and superconducting transport properties for growth of YBCO single-layer films was investigated. A technique to avoid the formation of CuO_x surface particles by using lyttrium-rich targets and N₂O in the sputtering gas without any deterioration of superconducting transport properties has been developed. The avoidance of these commonly observed surface particles is a necessity for all investigations and applications of layered structures having layers deposited on top of a YBCO layer.

Formation of a cubic ( or pseudo-cubic) phase with a lattice parameter of 0.414 nm was found in YBCO/STO multilayers. Chemical analysis showed the presence of Ba, Ti, 0 and Y in these precipitates, which was suggested to be Y-substituted BaTiO₃ (Y:BTO). Also, formation of Y₂O₃ precipitates was found in the multilayers. Phase evolution studies during a ramped thermal anneal revealed that grain growth of Y:BTO and Y₂O₃ was triggered by the decomposition of YBCO. The STO layers were observed to be occasionally discontinuous in the as-deposited multilayers, indicating a three-dimensional growth mode. Strain in both the YBCO and STO layers were found, which is of importance for the superconducting properties of YBCO as well as the dielectric properties of STO.

Finally, strain relaxation of STO single-layer films in the 9.3-144.0 nm thickness range deposited on LaAlO₃ (LAO) substrates was investigated. It was found to follow the general trend of a predicted strain - thickness relation based on energy density balance considerations regarding misfit dislocations and lattice strain. The STO films on LAO substrates were also utilized in an investigation of different x-ray optics, which showed that a hybrid mirror monochromator in combination with a triple bounce analyzer crystal provides very good conditions for characterization of thin distorted films grown epitaxially onto substrates with high structural order.