Injection MOCVD: ferroelectric thin films and functional oxide superlattices

MOCVD is a suitable technique for the synthesis of functional metal oxide thin films. In the present paper, injection-MOCVD was proved to be an efficient method, not only to grow single layers, but also heterostructures and superlattices of functional oxide materials. We report on the deposition of BaxSr1−xTiO3 (BST) films and BaTiO3/SrTiO3 superlattices [(BTO/STO)n] obtained by injection MOCVD. In a first step, BST films were deposited on various substrates such as LaAlO3(LAO)(012), SrTiO3:Nb(STO:Nb)(001) and Al2O3(0001), resulting in epitaxial films in the case of STO or LAO substrates and highly textured films in the case of Al2O3 substrates. The good crystallinity of the films obtained was evidenced using X-ray analysis. Concerning the dielectric properties of BST films on STO:Nb, the Tc values were found to be the same as those for bulk materials. In a next step the feasibility of (BTO/STO)n superlattices was studied. The multilayers obtained were epitaxially grown on LAO and STO:Nb substrates. XPS was used to check in detail the pattern repetition of the superlattice and proved the low interface roughness of 1 nm as well as the absence of carbon contamination in the film. The measured periodicity of these superlattices were found to be in good agreement with simulation experiments. Further superlattices have been obtained by combining ferroelectric, magnetic (CMR) and superconducting (HTS) oxides. Typical results of these superlattices will be reported.