ZnO纳米棒/石墨烯异质结构的制备、调控及电光性能研究

ZnO nanorods are transparent, wide band-gap semiconductor nanomaterials, potentially useful for electronics and optoelectronics. Graphene is an emerging carbon material consisting of monolayered carbon atoms. Its atomic thickness and two-dimensional conjugated chemical structure cause a broad spectrum of attractive properties, such as optical transparency, high electro-conductivity, mechanical flexibility, and strong thermal/chemical stability. Architecture of ZnO nanorod/graphene heterojunction is a synergistic combination of the attractive properties of the both two materials and is expected to be used in next generation flexible optoelectonic devices. In these hybrids, graphene generally behave as a window electrode with efficient electrical and thermal conductivities, while the ZnO nanorod can provide additional electrical, optical, and catalytic functions. However, the present study is limited to the simple attempt use of the heterojunction and performance optimization in the relative devices, for the heterojunction itself little research has been reported. This project is to prepare flexible, stable, transparent ZnO nanorod/graphene heterojuncions by MOCVD and CVD techniques and several important problems will be precisely investigated. ①We will explore the growth parameters of the heterojunctions and their influence on the dimension, morphology, crystal quality, and flexibility. ②The interfacial constitution between ZnO and graphene layers will be investigated and the epitaxial relationship is expected to be acquired. By introducing O or Zn pre-deposition, we want to control the diameters and densities of the ZnO nanorods and optimize the mechanical flexibility. ③The Schottky contact barrier height, electrical transport property and their relationships with the interfacial compositions will be measured. ④The optical properties will be investigated and the mechanism of the plasma enhanced ultraviolet photoluminescence is expected to be proposed. This project aims to reveal the ZnO nanorod/graphene heterojunction preparation and control methods and its inner electrical, optical physics laws. It is expected to be helpful for the establishment of theoretical and technical basis for design and development of new high efficiency photoelectric devices.

ZnO纳米棒具有优异的光学性质，石墨烯具有优良的电学性质并且可变形，制备出高质量ZnO纳米棒/石墨烯异质结能够发挥两者协同效应，有望在高性能柔性光电子器件中实现重要应用。然而，目前的研究仅限于该异质结构在相关器件中的性能优化尝试，对于异质结本身的科学问题却研究甚少。本项目以MOCVD和CVD分别为ZnO和石墨烯的制备方法，通过研究该异质结构的制备工艺参数，致力于在柔性可形变石墨烯上获得具有高晶体质量、结构稳定的ZnO纳米棒阵列；揭示异质结界面处的原子排列方式，探明O和Zn预沉积方式对ZnO纳米棒晶体质量、维度、附着力度等的影响规律；获得ZnO纳米棒/石墨烯异质肖特基势垒高度及其影响因素，明确异质结电学和光学性能的影响因素，并阐明其影响机理。本项目旨在揭示ZnO纳米棒/石墨烯异质结的制备和调控方法以及其内在电学、光学物理规律，为新型高效光电器件的设计和开发奠定理论和技术基础。

半导体氧化物薄膜因其优异的光学和电学性质在太阳能电池、光催化剂、发光二极管、激光器、薄膜晶体管以及传感器等方面有许多潜在应用。其中，氧化锌和氧化钛因为无毒、稳定性好和性能优异等特点而备受关注。如何通过改善制备工艺和优化器件结构来提高材料性能一直是人们的追求目标。本项目采用MOCVD、磁控溅射、PLD以及化学法等技术制备了ZnO、TiO2、PbI2等薄膜，并对其晶体质量、光学以及电学性能进行了研究。这种研究对于了解薄膜生长特性、薄膜性质以及进一步开拓其实际应用具有重要指导意义。本项目主要取得以下研究成果。.1. 采用MOCVD技术，通过调节二乙基锌和氧气流量的大小可以控制ZnO薄膜的生长模式，通过改变源载气流量，可以实现纳米棒直径的改变，从150nm到20nm，均匀性良好。探索了SOI衬底代替Si衬底作为ZnO薄膜的外延衬底材料的可行性。.2. 采用湿法制备出了毫米长度量级的多层石墨烯纳米带。研究了不同NaOH溶液浓度对氧化石墨烯还原特性的影响，不同的NaOH/GO质量比会严重影响石墨烯的形貌，依次从薄片状变为褶皱装、带状和分离带状。.3. 研究了溅射功率和退火工艺对TiO2薄膜性能的影响。溅射功率增大，薄膜的结晶性能变好且内应力得到释放，吸收带边向长波长方向移动，有利于提高薄膜的光催化性能。退火温度的升高使二氧化钛的晶相由锐钛矿向金红石转变，600 ℃时为两相共存，锐钛矿相表现出了更好的光催化性能。.4. 研究了C-Mo双掺杂对TiO2薄膜光催化性能的改善作用。制备了不同掺杂浓度的溅射靶材，再采用磁控溅射方法制备了不同掺杂浓度的TiO2薄膜，当掺杂质量浓度为0.01%时，所得薄膜具有最小的禁带宽度和最佳的光催化性能。.5. 采用PLD技术在玻璃衬底上制备了PbI2薄膜，研究了不同薄膜厚度的光学吸收特性，推算了禁带宽度，并对其横向和纵向电阻率进行了测试。.6. 采用PLD技术在蓝宝石衬底上制备了Ti2O3薄膜，通过XRD和TEM分析了外延薄膜与衬底的晶面对应关系，利用紫外-可见分光光度计测试了其吸收和透过特性，利用变温霍尔效测试了其电学性能。.7. 通过XPS测试了TiO2/FTO异质结界面的能级不连续差，并且研究了退火对带价大小的影响，发现退火使得导带带阶增大，而这种增大导致异质结间的接触电阻也随之增大。