Low-Temperature Synthesis and Optical Properties of Gel and Ceramic Photonic Crystals Made up of High Dielectric Constant Materials

1)前驱体溶胶溶液的合成：以异丙醇钛、钛(O-i-Pr)_4、聚乙二醇(PEGg：摩尔质量=400)为原料，制备了二氧化钛前驱体溶液。以乙二醇单甲醚为溶剂和水对醇盐进行水解，得到组成为Ti(O-i-Pr)_4：EGMME：H_2O=1：3：1(摩尔比)的BaTiO_3前驱体溶液，并用与BaO_2H_2相同的方法制备了BaTiO_3前驱体溶液。将这些前驱体溶液旋涂在硅和镁衬底上，得到了不同材料的无裂纹凝胶膜。2)抗蚀剂的制备：我们首先在Si-μ上旋涂制备了约1…m的抗蚀剂膜然后用电子束曝光法在抗蚀剂衬底上形成具有不同气孔半径r和气孔间距(晶格常数)a的六角形气孔阵列。3)二氧化钛和钛酸钡凝胶光子晶体的制备：通过将前驱体溶胶溶液浇注到抗蚀剂模具中，干燥，干燥，制备了由二氧化钛和钛酸钡前驱体柱状六角阵列组成的二维光子晶体。然后用脱模剂进行化学脱模。在脱模之前，需要完全脱除在抗蚀剂模具上形成的GAL膜，我们利用CF4/C3F8气体的干法刻蚀技术成功地将其刻蚀出来。4)二氧化钛和钛酸钡陶瓷光子晶体的制备：通过在空气中500-800℃的温度下烧结前驱体GET，获得了二氧化钛和钛酸钡陶瓷光子晶体。所得到的光子晶体没有明显的晶格无序，前驱体几乎没有坍塌，但由于在烧成过程中收缩，柱子的大小发生了显著的变化。5)光学性能的评价：对不同rand值(r=110 nm，a=400 nm)，(125 nm，450 nm)和(125 nm，500 nm)的二氧化钛陶瓷光子晶体和a=450 nm，rl=0.19的BaTiO_3陶瓷光子晶体在TE模和TM模的Γ-M和f-K波长范围内的光学反射进行了测量其中所有光子晶体在计算的波长附近都观察到了明显的反射峰。实验结果表明，本研究首次成功地制备了具有壁面光子带隙的二维陶瓷光子晶体。较少

The objective of this study is to establish a low temperature synthesis method for fabricating two-dimensional TiO_2 and BaTiO_3 gel and ceramic photonic crystals by sol-gel processing using resist molds and also to evaluate the optical properties of the obtained crystals.The obtained results are summarized as follows:1) Synthesis of precursor sol solutions : We prepared a TiO_2 precursor solution by mixing titanium isopropoxide, Ti(O-i-Pr)_4, poly(ethylene glycol) (PEG: molar weight=400), ethylene glycol monomethyl ether (EGMME) as a solvent and water for hydrolysis of the alkoxide to have the composition Ti(O-i-Pr)_4: EGMME : H_2O = 1:3:1 (in molar ratio), and also prepared a BaTiO_3 precursor solution by using the same procedure with barium ethoxide, Ba(OC_2H_5)_2. These precursor solutions gave crack-free gel films of the respective materials when spin-coated on Si and MgO substrates.2)Preparation of resist molds : We first prepared resist films of around 1μm by spin coating on Si … More and MgO substrates, and then formed hexagonal arrays of air holes with various values of air holes radius r and spacing between holes (lattice constant) a in the resist alms using electron beam lithography. The values of r and a of the resist molds produced were theoretically determined from photonic band structure calculations to allow the photonic crystals to be fabricated exhibit complete photonic band gaps in the visible region.3)Fabrication of TO_2 and BaTiO_3 gel photonic crystals : We succeeded in fabricating two-dimensional photonic crystals consisting of hexagonal arrays of TiO_2 and BaTiO_3 precursor pillars on Si and MgO substrates, respectively, by casting the precursor sol solutions into the resist molds, drying, then followed by removing the resist molds chemically with a removal agent Prior to the removal of resist molds it is necessary to remove completely a gal film that the present method unavadably form on the resist mold, and we succeeded in ding it with a dry etching technique using CF_4/C_3F_8 gas.4) Fabrication of TiO_2 and BaTiO_3 ceramic photonic crystals : TiO_2 and BaTiO_3 ceramic photonic crystals were obtained by sintering the precursor get photonic crystals at temperatures of 500 to 800℃ in air. The obtained photonic crystals showed no appreciable lattice disorder of the crystals, with little collapse of the precursorpillars, though significant changes in the size of the pillars due to their shrinkage during firing were observed5) Evaluation of optical properties of the obtained photonic crystals : Optical reflection measurements in the wavelength range of 400 to 1000nm were carried out for TiO_2 ceramic photonic crystals with different rand a values of (r=110nm, a=400nm), (125nm, 450nm) and (125nm, 500nm) and for a BaTiO_3 ceramic photonic crystal with a=450nm and rl=0.19 in the Γ-Mand f-Kdrections of the crystals for both TE and TM modes, in which distinct reflection peaks were observed for all the photonic crystals at around wavelengths calculated. The results dearly demonstrate that 2D ceramic photonic crystals with wall-developed photonic band gaps in the optical regime have been successfully fabricated for the first time in this study. Less