氧化锡低维结构中激子发光的量子调控与紫外发光器件研究

The aim of this project is to grow the SnO2 quantum dots (QDs) and ultra-thin films (UTF) with high quantum yield (QY) exciton emission by physical vapor deposition and atomic layer deposition technique, upon which to build the SnO2-based homo-junction light-emitting devices; to study the photoluminescence properties of exciton and surface states and defects-related emissions, and to analyze the manipulation of 0- and 2-dimensional quantum confinement effect on the QY of the exciton emission; to investigate the relationship between the size, shape, density of QDs, the thickness of UTF and the peak energy and QY of the exciton emission, to reveal the origin, defect level and activation energy of emissions from surface states and defects in SnO2; to establish the correlation of emission intensity of surface states and defects with the dimension and shape of the low-dimensional structures; to design and fabricate the homo-junction light-emitting devices based on SnO2 low-dimensional structures, and to unveil the influence of environment, temperature and electrode on the device performance. Due to the wide band gap, high exciton binding energy, outstanding optical and electrical properties and high stability of chemical and physical properties, SnO2 is a promising material for next generation nonpolar ultraviolet (UV) light-emitting devices. The research on SnO2 low-dimensional structures with high QY exciton emission is significant for both science and technology application. The project will provide some basis on the development of SnO2-based deep UV optoelectronic devices.

本项目采用物理气相沉积和原子层沉积技术生长高量子效率激子发光SnO2量子点和超薄薄膜，构建SnO2同质结发光器件；研究SnO2低维结构中激子、表面态和缺陷相关的发光性能，探讨低维限域效应对激子发光效率的量子调控作用；研究量子点尺寸、形状和密度，超薄薄膜厚度等与激子发光峰位、宽度和量子效率的变化关系；可变环境原位研究SnO2低维结构中与表面态和缺陷发光性能，揭示发光峰来源，确定能级位置和激活能大小，建立低维结构的尺度、形态与表面态或缺陷发光峰强度之间的关系；设计构建基于SnO2低维结构同质结器件，获得紫外电致发光，揭示环境、温度、电极等对器件性能的影响。SnO2具有带隙宽、激子结合能高、光电性能优异和物化性质非常稳定等特点，非常适合构建下一代非极性紫外光电子器件。研究SnO2低维结构高效率激子发光具有重要的科学意义和应用价值，通过本项目的实施将为SnO2基深紫外光电子器件的实现奠定一定基础。

二氧化锡（SnO2）是一种宽禁带半导体材料，具有带隙宽、激子结合能高、光电性能优异和物化性质非常稳定等特点，适合应用于构筑下一代紫外光电器件。本项目生长尺寸小于（或接近）激子波尔半径的SnO2量子点，量子点具有高强度300 nm波长深紫外发光性能，量子效率达到21%。研究尺寸对发光强度的影响，观察到量子点尺寸长大导致的激子发光静默现象。实验确定SnO2量子点的激子结合能为147 meV，意味着SnO2可应用于高温发光器件。研究量子点超薄薄膜高温（>300 K）发光性能，观察到强局域化导致荧光发射峰反常移动现象，计算出局域化能阱深度为91 meV。构筑SnO2量子点/PEG组成的波导型薄膜，研究光泵浦下SnO2量子点发光行为，观察到波长位于305 nm处低阈值（0.8 MW/cm2）放大的自发辐射现象。SnO2是一种偶极跃迁禁戒的直接带隙半导体，我们的研究结果证明了量子限域效应可以打破SnO2中跃迁禁戒，获得高效率深紫外发光材料，并应用于构筑激光器件。此外，我们采用物理气相沉积生长SnO2薄膜，SnO2薄膜表现出高可见光透过率（>85 %）和高电阻（2.1E9欧姆）的特点，可应用于薄膜太阳能电池的缓冲层。构筑SnO2基紫外光探测器件，280 nm波长紫外光响应度达到60 A/W，外量子效率29000 %；探测率达到6.1E15 Jones，比目前商用硅基紫外光探测器（~ E12 Jones）要高3个数量级。器件的动态范围高达195 dB，意味着器件不仅可检测极其微弱的紫外光（等效每秒300紫外光子），对于较强的紫外光也可以探测。研究乙醇气氛环境下，SnO2薄膜表面残余载流子的演化行为，观察到乙醇分子被光生空穴氧化成为乙醛和乙酸的过程，通过该过程大大加速器件的恢复速度。