Dielectric and Structural Properties of SrTiO3 Thin Films Grown by Laser Molecular Beam Epitaxy

Here I will review recent progress on the study of dielectric SrTiO3 （STO） thin films. In our work, laser molecular beam epitaxy has been used to prepare multilayer heterostructures consisting of dielectric STO and high temperature superconducting YBa2Cu3Oy （YBCO） thin films for tunable applications. Since the tunability of the dielectric constant and dielectric loss of STO are the key parameters determining the performance of tunable devices and hence the feasibility of this technology, the correlations between the deposition parameters of STO thin films, their structural characteristics, and dielectric properties were studied. An enhanced tunability of 74.7%, comparable to that of STO single-crystal, was observed in our grown STO thin films suitable for tunable YBCO applications. On the other hand, we have grown epitaxial STO （110） films on Si without any buffer layer. The nature of epitaxial growth and interfacial structures of the grown films were examined by various techniques, such as Laue diffraction, high-resolution transmission electron microscopy （HRTEM） and x-ray photoelectron spectroscopy. The in-plane alignments for the STO （110） films grown directly on Si （100） was found as STO//Si and STO//Si . HRTEM study has showed a crystalline transition across the STO/Si interface, indicating it is free from any amorphous oxide layer. We provide clear evidence that the interface mainly consists of Sr silicate phase. The results suggest that such Sr silicate interfacial layer exhibits favourable structural and chemical properties that are particularly useful for epitaxial STO （110） growth on Si. Such STO thin films will be useful for practical applications.