| Summary: | 碩士 === 大同大學 === 光電工程研究所 === 90 === Since BaTiO3 has excellent properties, including the electro-optic effect, the acousto-optic effect, the non-linear optic effect and the piezoelectricity, it is one of the key materials in integrated optics for applications such as electro-optic modulation, optical switching, frequency doubling and optical information storage. In comparing with bulk materials, thin films have several advantages such as small size, low cost, easy doping and multi-layer structure. Thus we hope to deposit BaTiO3 thin film for further applications. We choose the Si and GaAs as the substrate, because we hope to integrate with the mature I.C. technology. In consideration of lattice mismatch during film growth, we choose MgO thin film as the buffer layer. Additionally, we try to deposit BaTiO3 thin film at lower temperature and treat it by post annealing process to testify the thin film structure and quality.
In our experiment, we successfully deposited preferential orientation MgO(200) thin film on Si substrate at temperature, RF input power and pressure 450℃, 150W, 18 mTorr in pure Ar condition and on GaAs substrate at 350℃,150W, 5 mTorr in pure Ar condition. Next we also successfully deposited preferential orientation BaTiO3 on Si substrate with MgO buffer layer at temperature, RF input power, pressure and gas ratio 450℃, 150W, 5 mTorr and Ar:O2=4 respectively. The FWHM of the peak which was measured by XRD is 0.34º. We also used Raman scattering technology to confirm the thin film with poly-phase, tetragonal and orthorhombic.
We also deposited BaTiO3 thin film at lower temperature 200℃ and annealed the thin film at furnace. At the annealing condition 600℃ for 2 hours we improve the dielectric constant from 12 to 50 and observe the P-E hysteresis loop successfully.
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