基于柔性衬底的ZnO横向纳米线阵列的高效构筑、性能及其在高灵敏光电导器件中的应用研究

Metal oxide nanowires are promising building blocks for future photodetectors with small-size and low power-consumption, arising from their unique properties and one-dimensional geometry. The deeper understanding of nucleation theory of bottom-up approach allows us to fabricate various kinds of metal oxides with varying band gaps that covers inferred to deep UV light. However, challenges still exist for building practical high-performance photodetectors. For examples, the homogeneities of devices, how to fully explore the photoconductivity properties? et al. Herein, we would like to tackle these issues by following strategies. A pyramid PDMS mold is utilized to prepare ZnO nanowire arrays (on flexible substrate) with uniform diameter. Contact printing is applied to in-situ form horizontal nanowire arrays devices. This approach can overcome the inhomogeneity of device obtained through spontaneous nucleation growth. After that, we plan to systematically tune the diameter, strain and gate voltage to manipulate the band gap, Fermi level, position and density of defect/surface states, which are crucial physical parameters that determine the photoconductivity properties. By comprehensively analyzing diameter, strain, gate voltage dependent photoconductivity, photoluminance measurement and electrical simulation, we can gain deep insight in photoconductivity mechanism, which is supportive for enhancing the photoconductivity properties, and provide an approach to design high-performance photodetectors. The present proposal can provide useful insight on fully exploring the photoconductivity of metal oxides and designing guidelines for high performance photodetectors.

金属氧化物纳米线因优异的光电性能及独特的一维构型，而成为构造下一代小型、低功耗光电导器件的核心单元之一。对至下而上自组装理论的深入认识，使合成带隙覆盖红外-深紫外波段的多种纳米线变得可能，但是在构筑高效、实用的光电导器件仍面临着许多挑战：比如器件的均一性，如何最大幅度挖掘光电导性能等。本项目拟用金字塔PDMS模子实现直径均一、可调的ZnO纳米线阵列在柔性衬底上的生长，经原位平面化后，构建出横向纳米线光探测器阵列，消除自发形核带来的直径及性能不均一性。在此基础上，通过直径、应变、门电压三大调控手段来系统调节材料的光学带隙、费米能级、缺陷态、表面态能级位置、态密度等重要物理参数，结合光谱及电学模拟，阐明调控参量与光电导性能的物理机理，提取出提升光电导性能的手段，通过优化设计出高灵敏度的光探测器件。本项目对深度挖掘材料的光电导性能具有重要意义，并为实际应用提供了技术和理论策略依据。

本项目针对半导体微纳器件应用面临的两个瓶颈——平面型微纳阵列的高效“原位”构筑、及材料缺陷对器件性能的影响规律，并行开展了ZnO/卤化物钙钛矿微纳阵列的原位构筑、面向气体分子识别检测的氧化物纳米材料表面缺陷调控的研究工作，取得了如下研究成果：1、本项目首次利用简单的压印膜厚控制的方法，获得PDMS金字塔上蕴含的渐变的精细结构，可用单一PDMS模子获得尺寸（~0.1 – 1 μm）准连续可调的压印图形，大幅降低了纳米蚀刻的准入门槛，成功构筑了ZnO纳米线阵列；2、鉴于光电性能优异的卤化物钙钛矿无法采用传统光刻工艺，利用平面衬底上的亲水-疏水图形，成功实现了卤化物钙钛矿前驱体溶液在平面衬底的选择性浸润，通过控制溶剂的挥发驱动卤化物钙钛矿的缓慢结晶，得到了高结晶、平面型卤化物钙钛矿微米阵列。卤化物阵列光电探测器对555nm的可见光响应率可达1 A/W，探测率在1011 Jones 以上。钙钛矿阵列通过低温溶液法生长，柔性衬底兼容，满足大规模工业化生产，为下一步研究门电压、应力对材料性能的调制及开发实用型光电器件奠定了重要基础；3、缺陷是影响材料光电及其它性能的重要因素，理清材料不同缺陷对器件性能的影响规律与机制是开发高性能半导体纳米器件的关键。本项目系统研究了金属氧化物半导体中不同缺陷对其气体分子响应性能的影响，发现并验证了单电离的氧空位为活性位点，并发展了多种表面氧空位调控手段，可显著提升传感器的灵敏度（最高可提升2个数量级）及检测限（部分气体可达10ppb）。.相关研究不仅为基于阵列型半导体微纳器件的原位构筑，也为其它光电、生化集成器件的研发进行了有益尝试。缺陷研究对深度挖掘材料的性能、大幅提升器件的性能具有重要的意义，可为实际应用提供理论依据与技术支撑。

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