【作者】 谢荣国；

【导师】 蒋民华； 杨德仁； 关口隆史；

【作者基本信息】 浙江大学 ， 材料物理与化学， 2006， 博士

【摘要】 光子晶体由于具有独特的调节光子传播状态的功能,是光电集成、光子集成和光通信的基础材料。本论文主要研究了单分散SiO₂微球、SiO₂@CdS核壳微球和CdS空心球等光子晶体用结构基元的制备方法,采用多种自组装手段制备了SiO₂蛋白石和CdS反蛋白石光子晶体,结合理论计算研究了它们的光学性质,并建立了在光子晶体中引入可控缺陷的方法,最后研究了光子探针的制备及光学性质。论文的主要创新性结果如下: 1.制备了粒径范围涵盖广（150nm—1μm）,相对标准偏差小于5.0%的SiO₂微球。以不同粒径的SiO₂微球为结构基元,采用重力沉积、离心沉积和垂直提拉沉积等自组装手段制备了可见波段蛋白石光子晶体。以表面具有微米级周期图案的硅片为衬底,采用垂直提拉法多次生长,在蛋白石光子晶体内部制备了可控的人工微缺陷。 2.建立了一种采用超声辅助化学水浴沉积制备SiO₂微球表面包覆CdS的核壳微球（定义为SiO₂@CdS）的新方法。该方法简单快捷,无需对SiO₂球表面化学改性,CdS壳层致密均匀且厚度可控,溶液中无游离CdS颗粒。采用稀释的HF酸将SiO₂@CdS核壳微球中的SiO₂内核择优腐蚀后,制备了单分散CdS空心球。所得CdS空心球具有较高折射率（n=2.45）和高空占比,粒径相对标准偏差小于5.0%,壳层厚度（10nm-60nm）可控,结构稳定,是一类新型的半导体基光子晶体结构基元。采用离心沉积法自组装,分别制备了由SiO₂@CdS核壳微球和CdS空心球组成的面心立方光子晶体。 3.建立了一种无模板直接制备CdS反蛋白石光子晶体的新方法。先将CdS空心球自组装成面心立方光子晶体,然后在400℃下热处理,使CdS空心球收缩,得到了具有高填充率的CdS反蛋白石光子晶体。该方法打破了采用蛋白石模板来制备反蛋白石光子晶体的传统,直接以高折射率材料为结构基元自组装制备三维光子晶体,避免了模板法中复杂的填充过程和破坏性的模板去除过程。微区反射光谱表明:由直径为400nm的CdS空心球组成的反蛋白石光子晶体在530nm和920nm附近存在两个[111]方向性带隙,与光子能带的理论计算结果相符。 4.建立了一种在CdS反蛋白石光子晶体制备可控点缺陷的新方法。在环境扫描电镜样品腔中引入一定压强（10Pa-100Pa）的气体,利用聚焦纳米电子束进行精密照射,实现了对CdS反蛋白石光子晶体中单个“原子”的精密控制,在反蛋白石光子晶体中可控制备了空位缺陷和杂质缺陷。研究了缺陷形成机更多还原

【Abstract】 Photonic crystals （PCs） have attracted much attention because of their ability to manipulate, confine, and control light. In this dissertation, three classes of monodisperse spheres, including SiO₂ spheres, SiO₂@CdS core-shell spheres and CdS hollow spheres, have been fabricated by chemical routes for using as building blocks for PCs. They have been self-assembled into three-dimensional （3D） face-centered-cubic （FCC） PCs. The optical properties of these self-assembled PCs have been investigated, and were compared with the theoretical calculations. Moreover, two methods of introducing well-defined defects in opal and CdS inverse opal PCs have been developed. Finally, monodisperse luminescent rare-earth doped spheres and luminescent rugby-like ZnO particles for photonic probes have been prepared, and their optical properties have been investigated. The significant results achieved in this dissertation are given as below:1. We have modified and optimized the traditional Stober method for preparation of monodisperse silica spheres. The obtained silica spheres are highly uniform with diameters ranging from 150-900nm and with relative standard deviation less than 5.0%. Opal PCs composed silica spheres have been fabricated by several self-assembly techniques, including gravity-sedimentation, centrifugation and vertical dip-coating methods, whose pseudo bandgaps have been controllably adjusted from blue to red optical regions by varying the diameters of the silica spheres from 190 nm to 310 nm. Moreover, well-defined micrometer-sized defects have been embedded in the interior of the opal PCs using a vertical dip-coating method.2. We have developed an ultrasound-assisted chemical bath depositon （CBD） method for the fabrication of monodisperse SiO₂@CdS core-shell spheres. Using this method, the thickness of the shell can be flexibly controlled from 10 nm to 60 nm by adjusting the reaction time, while substantially eliminating the unwanted separated CdS nanoparticles. The obtained SiO₂@CdS core-shell spheres were highly uniform with homogenous and dense CdS shells. It is believed that the ultrasonic irradiation plays a key role for the formation of homogenous and dense CdS shell onto the silica cores. Subsequently, monodisperse CdS hollow spheres were obtained by selectively dissolving the silica cores with a diluted HF aqueous solution. The obtained CdS hollow spheres are highly uniform, mechanically robust, and possess high refractive-index （n=2.45） and high air-filling ratio. Thesehollow spheres thus provide ideal building blocks for 3D semiconductor PCs. Both SiO2@CdS core-shells and CdS have been self-assembled into FCC structures by centrifugation, confirming the high quality of these building blocks for photonic applications.3. We have developed a simple way to fabricate inverse opal PCs. The method involves directly self-assembling of CdS hollow spheres into FCC PCs from solution and subsequently annealing at 400 °C to minimize the interstitial spaces between the spheres. With this method, the stable CdS inverse opals with high filling ratio and the size as large as 20umx20um have been obtained. It directly uses the high refractive-index semiconductor material as building blocks to self-assemble into FCC PCs, thus overcoming some of the problems associated with traditional templating methods, such as sophisticated filling process and destructive template-removal process.The micro-reflectance spectrum shows that the CdS inverse opal composed 400-nm hollow spheres possesses two pseudo bandgaps at 530 nm and 920 nm along [111] direction, which is consistent with the theoretical photonic bandgap calculations.4. We have developed a simple and straightforward method of precisely fabricating point defects in CdS inverse opal PCs with a variable pressure scanning electron microscope. Well-defined point defects, not only vacancies but also an individual impurity, were directly fabricated by electron-beam irradiation under a gas atmosphere. This method has proven extensively practicable for precisely processing many other materials, such as ZnO and Si. Judging from the various advantages, including high resolution （<200 nm）, the versatility of the fabrication process and the convenient in-situ control of e-beam for both observation and defect fabrication, we believe that this method holds great promise for the development of 3D PBG-based devices.5. We have developed a versatile yet simple approach for the fabrication of monodisperse luminescent beads doped with rare-earth （RE）. Using a negatively charged CdS porous shell surrounding silica cores as a host matrix, trivalent RE ions have been electrostatically adsorbed into the CdS/silica core-shell beads in the suspension. After annealing at 750 °C for 2 h, the RE-doped core-shell beads are encode with sharp and strong luminescence of RE3+. By varying the RE species, including Tb3+, Eu3+, Nd3+, Er3+ and （Tb3++Yb3+）, a wide varity of characteristic luminescences of RE3+ from visible to near-infrared region havebeen readily encoded into the core-shell beads. These highly luminescent and uniform RE-doped beads thus provide a new class of spectrum-rich photonic probes or light source for photonic applications.6. Uniform ellipsoidal ZnO microparticles have been synthesized in aqueous solution by sonication at the temperature below 80 °C. The obtained ellipsoidal particles are highly uniform with a hexagonal cross-section. The morphologies of the ZnO particles have been tailored from rugby-like ellipsoidal to half-ellipsoidal by increasing the TEA concentration. Moreover, a significant enhancement of ultraviolet （UV） emission has been observed in ZnO by a thermal treatment at 200 °C. Based on the thermal desorption spectroscopy results, the origin of this enhancement effect was attributed to the reduction of non-irradiative centers and hydrogen passivation through desorption of adsorbed water and hydroxyl groups. Finally, we have developed a simple technique of directly writing sub-micrometer UV emission patterns in ZnO that were prepared using a wet-chemical method. The technique utilizes an electron beam in SEM to precisely control the local desorption to enhance the UV emission in the ZnO samples. With this technique, we have not only created optical nanotags on individual ZnO nanorods, but have also written sub-micrometer （-400 nm） UV-emission patterns on ZnO films, while keeping the surface morphology unchanged. This patterning technique is a straightforward and highly efficient method without the use of sophisticated lithographic processes, and has proven extensively applicable in various chemically-grown ZnO samples.更多还原