Development for liguid phase epitaxy by solvent evaporation

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Because of high convenience and productivity, the epitaxial growth techniques possess high utilities for fabricating many electronic devices. The liquid phase epitaxy is one of the most useful method among these epitaxial techniques due to high growth rate and reproducibility. The solvent evaporation epitaxy, which has been developed by us, is conducted in a following simple way : a solid mixture of solute and solvent is plastered on a surface of substrate crystals and then the solvent is evaporated by heating them. Despite of the simplicity, only a few trials of this epitaxy have been reported and many points for developping the technique have remained. In this study, we applied the technique for several oxide systems. The (100) surfaces of MgO single crystals were used as a substrate and experiments on simple oxides of MnO, CoO and NiO, oxide-superconductors of the BSCCO system and a transparent conductive spinel of ZnGa_2O_4 were reported. From the results of this study, the following superior points became clear : 1) The method is simple. 2) Epitaxial growth proceeds reproductively when the experimental conditions are settled. 3) No further treatment for separating the epitaxed layers from the solutions is needed. On the other hand, the next disadvantageous points existed : 1) Solvent materials is important but limited. 2) Because of the high heating temperatures, unexpected chemical reactions often occur between films and substrates. 3) Uniform epitaxial growth proceeds only when the appropriate growth conditions are settled sharply. As a conclusion, the solvent evaporation epitaxy is actually a prominent method for preparing oxide crystal films. However, it also became clear that there remain many problems to produce perfect films for many devices.