本征富受主型氧化锌单晶微米管的制备方法、物性和机理研究

In this project，a novel technique for the growth of stable, reproducible, and high quality undoped acceptor-enriched ZnO single-crystal microtubes with length of several millimetres by optical vapour supersaturated precipitation (OVSP) is proposed and researched. Based on this, the unique electrical and luminescence properties and mechanism of as grown ZnO single-crystal microtubes will be revealed. First, the growth model of OVSP will be established and the growth conditions of OVSP will be analyzed and designed through theory. Second, the growth law of acceptor-enriched ZnO single-crystal microtubes will be summarized through experiment with using the floating zone furnace or self-made OVSP equipment. Then, the structure, electrical and luminescence properties and mechanism will be characterized and studied by analysing the energy level structure of ZnO microtubes. Moreover, the inner mechanism of the stability problems will be researched by studying the effect of external environment on properties for acceptor-enriched ZnO microtubes. Finally, novel ZnO-based photocatalysts will be fabricated and characterized, the potential application of the acceptor-enriched ZnO microtubes will be explored. The research results of this project will not only provide theoretical and experimental support for the intrinsic defects of ZnO formation mechanism and its unique luminescence, but offer technology guarantees for develop novel ZnO-based device and broaden fabrication route for stable p-type ZnO single-crystal.

本项目提出并研究一种生长长效稳定、可重复、高质量、长度为毫米级的本征富受主型ZnO单晶微米管的新方法──光学气化过饱和析出法（OVSP）；在此基础上，研究该种微米管的电学、发光性质与机理。首先，从理论上建立OVSP生长模型，分析并设计OVSP生长所需条件；然后，依托光学浮区炉和研制的OVSP装置，从实验上摸索本征富受主型ZnO单晶微米管的生长规律；之后，对所生长ZnO单晶微米管的结构、形貌、电学和发光性质等进行表征，分析本征富受主型ZnO单晶微米管的导电与发光机理；随后，研究外部物理场对所生长ZnO微米管电学和发光性质的影响，探讨其受主态稳定的条件与机理；最后，制备以该种ZnO微米管为基的复合半导体光催化剂，研究其光催化性能。本项目研究将为本征富受主型ZnO单晶微米管的制备提供拥有自主知识产权的技术基础，同时探索制备大尺寸稳定可重复p型ZnO新途径。经文献和专利检索，目前还未见相关报道。

本项目提出了一种生长场效稳定、可重复、高质量、长度为毫米级的本征富受主型氧化锌（A-ZnO）单晶微米管的新方法：光学气相过饱和析出法（OVSP），具体研究成果包括：（1）全面揭示其生长机理，实现ZnO富受主稳定态，发现了浅受主态来自ZnO价带顶127meV处的本征锌空位缺陷，具有很高的时效性和稳定性。（2）对生长工艺进行优化，获得壁厚仅为~450 nm的超薄壁A-ZnO微米管；提出快速生长超薄壁A-ZnO微米管的新工艺：原位光学气象过饱和析出法（IOVSP），生长时间节约50%以上，有效提高微米管制备效率；提出超薄壁微米管固相法掺杂技术，随着施主元素的掺入，源于Zn空位的受主态被显著抑制，A-ZnO微米管从富受主型变为电阻率可控的n型半导体。（3）发现了自吸收效应对A-ZnO微米管中激子荧光的调控作用，揭示了自吸收效应是提高微米管微腔激子态密度、增强激子散射几率、实现低阈值自发辐射光放大的有效途径；发现A-ZnO微米管是一种可支持多种光学谐振模式的新型微腔，实现了精确温度调控多彩高效荧光，观察到了超低阈值紫外波导型光学回音壁模式的激射，构建了A-ZnO微米管基片上微流道光催化降解系统。（4）提出激光辐照微米管表面微纳结构制备技术，实现了A-ZnO微米管的缺陷密度和电阻率调控，有效提高A-ZnO微米管光电探测灵敏度和光催化降解性能。（5）构筑A-ZnO/n-ZnS的II型异质结器件，深势阱结构更易于促进光生载流子分离，有效提升光催化降解速率。（6）通过多声子协同隧穿效应实现A-ZnO微米棒电子激发，在高温工作环境中展现出高效电致发光特性；通过掺入浅施主Ga能级，进一步实现了热隧穿激发的多能级本征电致发光器件。揭示了焦耳热主导的电——热——光多物理场耦合机制，明确了电子-声子相互作用与隧穿温度阈值、缺陷态浓度与发光成分之间的内在联系，在开发基于热隧穿效应的稳定半导体光源方面建立了理论模型并提供了实验依据。（7）自主研发了以近红外激光为加热源的激光诱导气相过饱和析出生长系统（LVSP），激光光源可以有效改善反应速率，实现了高产率A-ZnO单晶微米棒/管生长。本项目的完成为基于A-ZnO微米管的新型高性能光电子器件的材料制备及设计奠定了技术基础并提供了新思路。