Development of Fabrication Technique of Crystals for Advanced Optical Computing

采用脉冲激光沉积(PLD)方法制备了钛酸钡晶体薄膜，它是光学计算的重要材料。2001年的实验结果表明，只要采用常规的PLD方法，衬底温度在665℃以上是获得晶态薄膜的必要条件。因此，在2003年的实验中，我们试图通过用相对较弱的紫外光照射基片表面来降低这一温度。用于靶照射的KrF准分子激光被分束器部分分开，以25~100 mJ/cm2的能量照射基片。用X射线衍射仪和扫描电子显微镜(SEM)对得到的薄膜进行了表征，成功地将晶化开始的温度分别降低到了600℃和250℃，光强为25 mJ/cm2。扫描电子显微镜观察表明，薄膜具有较弱的周期性结构，这种周期性结构受衬底取向的影响。综上所述，通过本研究，与常规方法相比，弱紫外光照射衬底可以降低结晶温度。

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.