自支撑硅氧碳纳米镶嵌复合薄膜的氧空位调控与发光机制研究

Silicon carbide (SiC) films with a combination of unique physicochemical and mechanical properties are well known as an important ceramic coatings for applications in the next generation of high-power, advanced optoelectronic devices and power microelectromechanical systems (MEMS). Considerable current attention has been focused on reducing the mismatches of thermal expansion coefficient and lattice constant resulted from heteroepitaxial techniques and improving the luminescent efficiency of SiC films. In the present study, a novel technique based on melt spinning of precursor was introduced to produce freestanding β-SiC/SiOxCy/Cfree nanocomposite films which could avoid the significant difference of thermal expansion coefficient between SiC and substrate. The as-received films exhibit several advantages such as wide band gap, high density of the oxygen mono- and di-vacancy defect centers, good radiation resistance, high hardness and chemical inertness. The structural-functional freestanding nanocomposite films are also explored as one of the most outstanding luminescent materials to improve the blue luminescent efficiency and stability. The radiative recombination of carriers can be ascribed to the oxygen mono- and di-vacancy from SiOxCy at the surfaces of β-SiC nano-crystals, whereas the photogeneration of carriers occurs in the β-SiC nano-crystals cores. To further identify the surface state and investigate the occurrence of oxygen vacancies in more detail. The photoluminescence (PL) properties and mechanism of samples derived from different precursors will be demonstrated through their microstructure and spectroscopy analysis. Effects of oxidation time, doping, sintering and annealing temperatures on the physicochemical properties and microstructural evolution of the SiC films will be further investigated. Much of analysis and discussion will then reveal the factors related to the PL properties and microstructural evolution of the films. Results will help to explore the SiC blue-emitting mechanisms and the oxygen mono- and di-vacancy defect centers from SiOxCy surrounding the β-SiC nano-crystals. The obtained freestanding β-SiC/SiOxCy/Cfree nanocomposite films are expected to have important applications in advanced optoelectronic devices, MEMS, source of blue light and such complex shaped-materials.

降低晶格错配和提高发光效率是当前SiC薄膜广泛应用于微机电系统（MEMS）及高温短波光电子器件等领域的研究重点，项目针对SiC薄膜/基材界面缺陷多及发光效率低的难题，以聚碳硅烷（PCS）和改性PCS为原料，基于先驱体熔融纺膜技术制备出新型硅氧碳纳米镶嵌复合薄膜，具有禁带宽度及氧空位发光中心密度大、致密度高、自支撑及化学稳定性好等结构功能一体化特性，以及纳米β-SiC镶嵌SiOxCy/Cfree复合结构模型。采用不同分子结构PCS来调控薄膜氧空位的形成和发光性能，获得多空位硅氧碳纳米镶嵌复合薄膜先驱体分子结构的设计准则。着重研究薄膜氧空位浓度对其发光特性的影响机制，并获得薄膜发光宽带隙模型与双空位缺陷中心发光机理，阐明其关键控制因素，探讨提高光电性能的有效措施，研究结果可指导复合薄膜的质量控制和组分、微结构的创新设计，实现其发光稳定与效率增大以及在高温蓝紫光学器件、MEMS等领域的成功应用。

SiC作为一种极具发展潜力的第三代宽带隙半导体材料，因其具有禁带宽度大、热导率高、耐高温、抗辐射和化学稳定性好等特性而成为制作大功率半导体器件的理想材料，已广泛应用于微机电系统（MEMS）、高温短波光电子器件及发光二极管等领域。降低晶格错配和提高发光效率是SiC薄膜广泛应用于MEMS及光电子器件的研究重点，项目针对当前SiC薄膜制备工艺复杂、薄膜/基材界面缺陷多及发光效率低的难题，以聚碳硅烷（PCS）和聚铝碳硅烷（PACS）为原料，并从PCS原料合成阶段引入稀土元素、液态PCS及芳香基团改性，基于课题组开发的具有自主知识产权的先驱体熔融纺膜技术制备了系列新型硅氧碳纳米镶嵌复合薄膜，具有独特的纳米β-SiC等轴晶镶嵌SiOxCy/Cfree基体复合结构模型，禁带宽度及氧空位发光中心密度大、致密度高、自支撑及化学稳定性好等结构功能一体化特性，并与硅集成电路工艺兼容。本项目按研究计划顺利完成了不同分子结构PCS及改性PCS的化学合成和分子结构表征，并对薄膜氧空位的形成和发光性能进行了有效调控，获得了多空位硅氧碳纳米镶嵌复合薄膜先驱体分子结构的设计准则。对不同工艺的系列硅氧碳纳米镶嵌复合薄膜进行了发光特性研究，并结合微观结构及光谱学分析对其缺陷态双氧空位发光模型与机理进行了探索。深入研究了交联预处理条件、裂解温度及异质掺杂等因素对薄膜微结构和理化性能形成及其演变的影响规律，并着重研究了薄膜氧空位浓度对其发光特性的影响机制，获得了薄膜发光宽带隙模型与双空位缺陷中心发光机理，阐明了其关键控制因素，并提出了提高光电性能的有效措施。此外，对薄膜在高温环境中热氧化、环境性能和微结构演变进行了研究，掌握了其在高温环境下的失效机理，为薄膜在高温下使用性能改进提供理论依据，本项目研究结果为新型强光发射SiC纳米复合薄膜的质量控制和组分、微结构的创新设计提供了依据，对实现其发光稳定与效率增大以及在其在蓝色发光器件、紫外光敏器件及MEMS等领域应用具有理论意义和实际应用价值。