Homoepitaxial Alignment of SrTiO 3 Thin Films Prepared by Metallo-Organic Decomposition.
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HOMOEPITAXIAL ALIGNMENT OF SrTiO 3 THIN FILMS PREPARED BY METALLO-ORGANIC DECOMPOSITION.
GABRIEL BRAUNSTEIN AND GUSTAVO R. PAZ-PUJALT Corporate Research Laboratories, Eastman Kodak Company, Rochester, NY 14650-2132.
ABSTRACT We demonstrate the homoepitaxial growth of SrTiO 3 prepared by the method of metallo-organic decomposition (MOD). Thin films of SrTiO3 are prepared by spin-coating and thermal decomposition of a solution of metallo-organic compounds, on single crystal, oriented, SrTiO 3 substrates and subsequently heat treated at temperatures ranging from 650"C to 1100°C for 30 minutes. Heat treatment at 1100"C results in the formation of single-crystal SrTiO 3 , perfectly aligned with respect to the underlying substrate. Ion-channeling analysis shows that the transformation to singlecrystal material proceeds epitaxially from the coating-substrate interface towards the surface of the sample. Transmission electron microscopy (TEM) studies of partially regrown samples reveal two distinct phases: an epitaxially aligned single-crystal phase, adjacent to the substrate, and a polycrystalline phase on top. On the basis of these observations, it is proposed that the crystallization of the MOD films involves the competition between two processes: layer-by-layer solid phase epitaxy and random nucleation and growth of crystallites. Layerby-layer epitaxy is the predominant crystallization mechanism unless it is inhibited by extrinsic factors like the contamination of the interface between the MOD film and the single-crystal substrate.
INTRODUCTION Metallo-organic decomposition (MOD) is a solution deposition process that provides a simple, versatile, alternative for thin film growth [1]. The method consists in the thermal decomposition of a solution of metallo-organic (MO) compounds coated over a substrate. The coating process is carried out under ambient conditions without the need for complex and expensive equipment. The components are mixed at the molecular level facilitating the rapid and homogeneous formation of the inorganic compounds and the stoichiometry is easily controlled. Mat. Res. Soc. Symp. Proc. Vol. 249. 01992 Materials Research Society
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Deposition can be accomplished by a variety of simple methods, such as spin-coating, dipping, or spraying. Very promising results, demonstrating the formation of films of a variety of inorganic compounds, have been reported in the last few years [2-4]. In almost all cases, the reports were concerned with the formation of amorphous or polycrystalline films and very little has been reported about epitaxially aligned structures. It would be desirable to produce single-crystalline films by this method. Indeed, partial epitaxial orientation of superconducting MOD films of YBa 2 Cu 3 07.x grown on MgO and SrTiO3 [5,6] substrates have been already reported. In a previous work [7] we described the process of formation and crystallization of MOD films of SrTiO 3 on Si substrates and presented preliminary evidence for the homoepitaxial alignment of these films on, oriented, s
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