Preparation Of Stoichiometric Lithium Niobate Thin Films

In this thesis, the history of lithium niobate was briefly reviewed and the basic properties, preparation and research survey of lithium niobate were summarized.The principle of sputtering technology and its application in lithium niobate thin films preparation were introduced.The lithium niobate thin films were prepared on Si(100) substrates as well as Si(100) substrate with SiO2 buffer by circle intermittent R.F.sputtering system under different experimental conditions. The lithium niobate thin films were successfully obtained by improving the experimental parameters. The micrstructure of lithium niobate thin films were investigated by XRD. In the end, the influence of experimental parameters on growing of lithium niobate thin films were studied.The main results were:With increasing of substrate temperature, the c-orientated degree of lithium niobate thin films increased and then decreased after 500℃. In the contrary, the diffraction peak intensity of LiNb₃O₈ decreased and then increased after 500℃. So we obtained the optimium growing temperature was 500℃.With increasing of the ratio of Ar and O₂, the probability of Ar⁺ bombarding target was enhanced. At the same time, the free distance of Ar+ became short. Ar⁺ and particles constituting the films dispersion aggrandized. If there were not enough O₂^-, it is difficult to form lithium niobate crystal.With decreasing of the ratio of Ar and O₂, the content of O₂ increased. When O₂ was excessive, the Li-deficient phase (LiNb₃O₈) was easy to be formed due to the reaction between oxygen and lithium.The results showed the optimium ratio of Ar and O₂ was 6:4.With decreasing of sputtering pressure, crystal quality became better and the Li-deficient phase disappeared gradually. We considered that 0.8 Pa was an optimium sputtering pressure.We introduced the SiO₂ buffer layer between substrate and lithium niobate thin films, and prepared the multiple structure of LiNbO₃/SiO-2/Si. The results showed that the LiNbO-3/SiO-2/Si film had(104)and(006)texture. Appropriate thickness of SiO2 buffer layer was good to the crystal quality of lithium niobate thin films.By a great deal of experiments, we optimized the growing conditions of lithium niobate thin films on Si (100) substrate or Si(100) substrates with SiO₂ buffer by R.F.sputtering system, namely that the substrate temperature was 500℃, the ratio of Ar and O₂ was 6:4 as well as the pressure was 0.8Pa. Additionally, we also investigated the influence of the thickness of SiO2 buffer layer on the crystal quality of lithium niobate thin films.