Preparation And Properties Of Ferroelectric Thin Films Of Silicon-based Optical Waveguide-based Study

Silicon based optical waveguide will play an important role in the integrated opt-electric devices in the future because of the superior performance of silicon material and the mature technology of the integrated circuit(IC) industry. Strontium barium niobate (Sr_xBa_1-xNb₂O₆, 0.22O₄ thin film was used as a buffer layer in SBN/MgAl₂O₄/Si structure as a try. Compared with SBN/MgO/Si structure, MgAl₂O₄ thin film can overcome the problem of crystal mismatch.Experiments mainly focus on thin film fabrication and the performance characterization, including buffer layer TiN thin film, MgAl₂O₄ thin film, ferroelectric SBN thin film and modified SBN thin film doped with Potassium and sodium. Thin film deposition techniques regarding experiment include the sol-gel and the magnetron sputtering, and thin film characterization techniques include X-ray diffraction (XRD), rocking curve, Atomic Force Microscope (AFM), Scanning electronic microscope (SEM), EDAX, spectrophotometer and four-probe resistances test.TiN thin film with (002) preferred orientation was grown by the DC magnetron sputtering at the condition of pure N₂ reacting gas, 1.6 A of the current of DC sputtering and 500 ℃ of the substrate temperature. Surface and cross-section morphology analysis indicted that thin film surface is void-free and the grains size is almost uniform, roughnesses are Ra: 1 nm, Ry: 9 nm, Rz: 9 nm, respectively (scanning scope: 500 nm×500 nm). The interface of TiN/Si was clear-cut, so TiN thin film was an appropriate buffer layer. The film growth was along c axis normal to the substrate indicating that thin film growth process was continual and the stress released totally. Resistivity wasmeasured as low as 30 uD-cm, so TiN thin film was proven to be used as bottom electrode.The (400) orientation MgA^C^ thin film was fabricated on the Si (100) substrates by the sol-gel technique. Structural characteristic of the MgAhC^ spinel thin films was measured by X-ray diffraction (XRD) and surface morphology of the thin films was characterized using an atomic force microscope (AFM). Results showed that surface was very smooth and the roughness was small enough. MgA^CU thin film was an approiate buffer layer for highly orientation SBN thin film fabrication.SBN thin films were prepared on MgO (100) and Si (100) substrates by the sol-gel technique. Thin film microstructure analysis indicated that KSBN thin films and KNSBN thin films fabricated on the MgO (100) substrate had highly preferred orientation, while SBN thin films on the Si (100) substrate displayed several orientation peaks. The orientation properties of the SBN thin films were improved with a buffer layer of KSBN thin film.Through the work presented in this thesis, many advances both at theory and practice were achieved. Finally, conclusions and advices for the future work were given.