Development of Fabrication Technique of Crystals for Advanced Optical Computing

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Crystalline barium titanate thin films which are very important materials for optical computing have been fabricated by the pulsed laser deposition (PLD) method. From the results which were obtained in 2001, it was found that the substrate temperature above 665 C^o was necessary to obtain crystalline films, as long as the conventional PLD was adopted. Therefore, in the experiments performed in 2003, we tried to reduce this temperature by irradiating the surface of the substrate with ultraviolet laser relatively weak intensity.The KrF excimer laser for the target irradiation was partially divided by a beam splitter and irradiated the substrate at a fluence from 25 to 100 mJ/cm^3. The obtained films are characterized with the X-ray diffractometer and the scanning electron microscope (SEM).The temperature at which the crystallization started was successfully reduced to 600^oC and 250^oC for the intensities of 25 mJ/cm^2, respectively. The SEM observation revealed that the obtained films had some weak periodical structures which were influenced by the orientation of the substrate.In summary, through this research, we could reduce the temperature of crystallization by irradiating the substrate with weak ultraviolet laser compared to the conventional method.