单根ZnO纳米线点缺陷的调控及其对光电性能与磁传输的影响

Semiconductor nanowires with a large aspect ratio and a diameter below 100 nm promise to be important in the next-generation nanometer-scale devices due to the numerous unique properties that are expected for these (quasi-) one-dimensional systems. Among various semiconductors ZnO, by virtue of its excellent material properties, such as a wide direct bandgap of 3.37 eV at room temperature, a large exciton binding energy of 60 meV as well as high electron mobility and high thermal conductivity, have attracted particular attention as a revival semiconductor. However, as a new semiconductor, further development of ZnO based applications still requires complete control and understanding of the defects and doping. In this project the density of native point defects (Zn and O vacancies and interstitials) will be varied through noble gas ion irradiation - with different ion mass and fluence - and post thermal annealing. The response of the ZnO nanowires to the ultraviolet light as well as to the visible light will be studied in a field-effect transistor configuration. Finally, the effects of the point defects on the magnetotransport of individual ZnO nanowires will be investigated, which includes temperature dependence of the resistance, magnetoresistance and spin injection measurements. Within this research project we want to obtain an improved understanding of the formation of point defects and its effects on optoelectronic properties as well as magnetotransport of ZnO nanowires, which is crucial for future ZnO based optoelectronic and spintronics devices.

半导体纳米线由于其特殊的尺寸与几何结构，有望成为纳米电子，纳米光电子等下一代新型器件的核心组成部分。ZnO材料由于其直接带隙结构、高激子束缚能、高电子迁移率等优点成为目前宽禁带半导体材料的研究热点。然而从材料研究的角度，围绕着缺陷、掺杂等方面ZnO的研究仍有许多亟待回答的关键科学问题。本项目选取ZnO纳米线为研究载体，通过惰性元素离子注入与后续热退火处理实现ZnO纳米线点缺陷的调控。在此基础上，通过研究单根ZnO纳米线场效应晶体管从可见到紫外波段的光学响应，揭示点缺陷与纳米线电学性能以及光响应的联系。最后，研究点缺陷对单根ZnO纳米线磁传输的影响，具体包括变温电学测试、磁电阻测试、自旋注入等方面。本项目针对ZnO材料目前存在的主要问题与面临的挑战，对其中部分关键科学问题进行深入研究，为ZnO纳米线在纳米电子与自旋电子学等方面的应用奠定基础。

ZnO材料由于其直接带隙结构、高激子束缚能、高电子迁移率等优点成为目前宽禁带半导体材料的研究热点。然而从材料研究的角度，围绕着缺陷、掺杂等方面ZnO的研究仍有许多亟待回答的关键科学问题。本项目选取ZnO纳米线为研究载体，通过惰性元素离子注入与后续热退火处理实现ZnO纳米线和ZnO单晶点缺陷的调控。本项目取得如下主要结果：1）通过表面增强拉曼散射(SERS)实现单根ZnO纳米线的拉曼测量，增强因子达1200。2）揭示了单根ZnO纳米线与黑磷量子点直接的电荷转移及其拉曼增强效应，研究表明该现象与ZnO纳米线中的缺陷态紧密相关，该结果首次报道了两种无机材料之间的协同拉曼增强效应。3）利用ZnO与单层磷烯量子点结合，构筑了三维组装结构的范德华纳米异质结。研究表明，该类异质结不仅可以有效分离光生激子、拓展光谱吸收范围，同时提升黑磷材料的抗氧化（普通放置50天不衰减）、抗辐照（多波长高功率激发无衰减）与抗高温（最高可耐730 K）能力。本项目首次将该材料应用在阻变型光调制存储器中，通过改变光照波长、强度等条件，有效调节了存储器的写入（SET）电压，使器件在紫外（380nm）到近红外（785nm）宽波段范围内均能有效工作，这是到目前为止最宽响应波段的光调制存储器。4）制备单根ZnO纳米线光电探测器，并通过缺陷工程实现优异的光电探测性能。在100 mV偏压下，单根ZnO纳米线光电探测器响应度达10E5 A/W ，探测度达10E15 Jones，实现nW/cm2级的探测灵敏度，并可通过场效应，调节该纳米线对不同波长光的响应行为。本项目揭示了缺陷在ZnO纳米线光电器件、自旋电子器件中的重要作用。