Preparation of (Pb,La)(Zr,Ti)O3 epitaxial thin films by modified sol-gel method and their crystallinity evaluation

The preparation of (Pb,La)(Zr,Ti)O-3 (PLZT) films has been widely investigated because of the expectation for their application to high-performance optical devices. We, prepared PLZT films on sapphire substrates by a newly developed modified sol-gel process with methanol, and the crystalline and optical evaluations of the films were performed in detail. In particular, relationships between the modified process and crystallinity were discussed. The crystalline orientation of the films obtained by our modified process was noticeably improved without enlargement of grain size. Thus, optical loss in the films also decreased by 15% using the modified process. In order to investigate crystal growth using the modified process, the observation of the surface state of sapphire by X-ray photoelectron spectroscopy (XPS) was performed. The At 2p on the XPS profile from the surface of the sapphire substrate was removed by surface treatment. It was found that the surface modification with organic molecules was caused by the methanol process. From the results, the effectiveness of modification treatments for the preparation of high-quality PUT films was revealed.