Preparation of Functional Ceramic Thin Films by Photo-MOCVD and their Applications to Optical Functional Devices

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Functional ceramic thin films, such as zinc oxide (ZnO), lead titanate (PbTiO_3) and lead zirconate titanate (Pb (Zr, Ti) O_3 ; PZT) have been obtained by photo-MOCVD. Using diethyl zinc, O_2, and NO_2, c-Axis oriented ZnO thm films were grown on glass substrates at 150ﾟC. ZnO epitaxialisms were also grown on sapphire substrates at higher than 450ﾟC. The observed effects of UV light irradiation on the growth were an increase in growth rate, an improvement in crystallinity and a change in electrical properties. In photo-MOCVD of ZnO, surface photochemical reactions play a more important role than gas phase photochemical Seactions.(111) oriented PbTiO_3 thin films with a perovskite phase were obtained at 600ﾟC by photoMOCVD using tetraethyl lead, titanium, isopropoxide and O_2. When NO_2 was used as an oxidizing 969, polycrystalline films with a perovskite phase were obtained a (530ﾟC. The crystalline quality and Pb/Ti compositional ratio were influenced by photo irradiation. It was found tfiat photo irradiation helped to reduce the growth temperature. Electrical properties of the films obtained were also investigated. The PbTiO_3 films showed good step coverage characteristics.Pb (Zr, Ti) O_3[PZT]thin films were also prepared by photo-MOCVD. By changing the gas flow rates of Zr 8Rd Ti, preferentially (111) oriented PZT films with a tetragonal phase were grown at 600ﾟC and films with a rhombohedral phase were grown at 650ﾟC. The observed effects of photo irradiation on the growth of PZT were an increase in growth rate and a change in film composition. PZT thin films with a thickness of 3000-6000* showed ferroelectric P-E hysteresis curves and switching characteristics.