基于n-ZnO/i-ZnS径向异质结构纳米线阵列的可见盲紫外光探测器研究

Radial heterostructure nanowire arrays have a huge potential application in photodetection due to their advantages, including a high carrier collection efficiency, a large heterojunction area, an excellent crystal quality and the light trapping. The applicant plans to synthesize n-ZnO/i-ZnS radial heterostructure nanowire arrays on cheap ITO glass substrates and on flexiable ITO coated polymer substrates by the simple and low cost hydrothermal method. The doping concentration and conductivity of the n-ZnO core can be tuned by changing the group III ion concentration in the precursor solution. The optimized growth conditions will be explored to obtain the i-ZnS shell with a high crystal quality and a controllable thickness. The radial heterostructure nanowire arrays grown on the flexible conductive substrates can be used to assemble flexible visible-blind UV photodetectors. The performance of the photodetectors will be measured. Next,we will study the relationships between the performance of the photodetectors and the crystal quality and thickness of the i-ZnS shell, the conductivity of the n-ZnO core, and the curvature of the photodetector, in succession. The transport mechanisms of photogenerated carrieres in the i-ZnS shell will also be explored. We will pay special attention to the influences of the heterojunction on the separation, extraction and recombination of photogenerated carrieres. Completing this project is beneficial to realizing the fabrication of low cost and flexible visible-blind UV photodetectors of high performance. It is significant in the military and civil fields.

径向异质结构纳米线阵列具有高载流子收集效率，大的异质结面积，高的晶体质量以及陷光结构等优势，在光探测领域有巨大的应用潜力。本项目拟采用简单、低成本的水热合成方法，在价格低廉的ITO玻璃和镀有ITO的柔性聚合物衬底上制备n-ZnO/i-ZnS径向异质结构纳米线阵列；通过调节反应溶液中III族金属离子的浓度，控制n-ZnO核层的掺杂浓度以及电导率；摸索在n-ZnO纳米线上外延生长高晶体质量厚度可控的i-ZnS层的生长条件。利用径向异质结构纳米线阵列制成柔性可见盲紫外光探测器，测试器件的性能，确立i-ZnS壳层的晶体质量以及厚度、n-ZnO核层的电导率、器件弯曲度等参数与探测器性能之间的关系。研究i-ZnS壳层中光生载流子的输运机制，确认异质结对光生载流子的分离、抽取、复合过程的影响。本项目为实现廉价高性能柔性的可见盲紫外光探测器奠定基础，具有很强的军事和民用价值。

本项目解决了以下几个方面的问题。（1）利用水热法在各种刚性衬底（ITO玻璃、AZO玻璃、GaN膜）及柔性衬底（PET膜、Kapton膜）上可控生长ZnO纳米线阵列。通过调控种晶制备参数及纳米线生长参数可以控制纳米线的尺寸。ZnO纳米线是单晶的，具有纤锌矿结构，沿[001]方向生长。吸收光谱显示纳米线的禁带宽度为3.32eV。测试光致发光谱，在378nm处观测到强的紫外发光，说明合成的纳米线具有较好的结晶质量。通过在生长溶液中添加Al3+离子，成功合成1%Al掺杂的ZnO纳米线阵列。（2）利用离子交换法成功获得了ZnO/ZnS径向异质结构纳米线阵列。硫化钠溶液中的S2- 离子会替代ZnO中的氧元素，将纳米线的表面硫化成ZnS。ZnO核仍为单晶，但ZnS壳层是多晶的。通过控制硫离子浓度、硫化时间及硫化温度可以控制ZnS壳层的厚度及壳层中ZnS颗粒的尺寸。光致发光谱显示来自ZnO的378nm紫外光发射强度随硫化时间的增加而迅速减小，说明ZnO/ZnS径向异质结构是II型异质结构，有利于电子和空穴分离。（3）成功利用合成的ZnO纳米线阵列及ZnO/ZnS纳米线阵列制成高度敏感的光探测器。ZnO/ZnS径向异质结构纳米线阵列基光探测器的敏感度（光电流与暗电流的比值）及响应时间都要优于ZnO纳米线阵列基光探测器，这归因于异质结构的存在。因此，异质结构纳米线阵列在紫外光探测上具有巨大应用潜力。