二维柔性ZnO纳米墙/石墨烯气敏传感器的缺陷协同及拮抗效应研究

Both the ZnO nanowalls and graphene are extinguishly active gas sensing materials. However, defects are always introduced unavoidably in the sythesis process. Heterojunctional gas sensors take posession of three dimensional gas transport channels when graphene is integreted with ZnO nanowalls.The synergistic and antagonism effect of the defects lied in ZnO nanowall and graphene would be generated while their physical and electrical properties were preserved for themselves, which had an important influence on the gas sensing performance of the heterojunctions. In this project, electron transport at the interface between ZnO nanowall and graphene are researched by constructing two dimensional soft ZnO nanowall/graphene heterojunction gas sensors. The synergistic and antagonism effect from the defects lied in the heterojunction on the carrier density is revealed. The function relationship between the carrier density and surface depletion width is researched. The interrelationship among synergistic and antagonism effect from the defects, carrier density and surface depletion width is built. The infuluence mechanism of synergistic and antagonism effect from the defects on the gas sensing performents of the two dimensional soft ZnO nanowall / graphene heterojunction is researched. Solving the above question, it has scientific significance for the interfacial physical properties. Moreover, it has important engineering application value for the development new gas sensors.

ZnO纳米墙和石墨烯作为优良的二维气敏活性材料，在制备过程中都会不可避免的引入各种缺陷。将石墨烯片和ZnO纳米墙结合，构筑具有三维立体气体传输通道的异质结构气体传感器，它们在保持各自的物理和电学性质的同时，驻存在异质材料中的双方缺陷必然会发生协同及拮抗效应，从而对异质材料的气敏性能产生潜在的重要影响。本项目通过构筑二维柔性ZnO纳米墙/石墨烯异质结构气敏传感器，研究ZnO纳米墙和石墨烯间的界面电子传输特性，揭示缺陷效应对二维ZnO纳米墙/ 石墨烯气敏传感器的电子载流子密度的影响机制，确立载流子密度与表面损耗层宽度间的函数关系，建立缺陷效应－载流子密度－表面损耗层宽度的内在关联性，研究影响二维ZnO纳米墙/石墨烯气敏性能的缺陷协同或拮抗作用机制。上述问题的解决对于研究两相界面间的物理性能具有重要的科学意义，对于发展新型气敏传感器具有重要的工程应用价值。

采用水溶液法制备出二维ZnO纳米墙，利用改善的Hummer法制备高质量的石墨烯，用原位生长的方法在还原石墨烯薄膜上生长ZnO纳米墙，进而构筑ZnO纳米墙/石墨烯异质结。利用SEM, HRTEM, PL, XPS等对ZnO纳米墙及石墨烯的形貌，微观缺陷和元素分布进行了系统表征，利用智能气敏测试系统对纯ZnO纳米墙、纯石墨烯和ZnO纳米墙/石墨烯异质结的气敏性能进行了研究，利用霍尔效应分析了石墨烯对ZnO纳米墙载流子浓度的影响，从理论上分析了ZnO纳米墙/石墨烯异质结的缺陷协同与拮抗效应。通过上述工作，获得以下结论：.1）利用水溶液法制备了二维ZnO纳米墙。ZnO纳米墙在285℃下对200ppm酒精的最大灵敏度达44.1，在220℃下，对50ppm的NO2最大灵敏度达30。利用改善的Hummer法制备高质量的石墨烯，石墨烯在140℃对NO2的最大灵敏度达1.67。.2）通过改变煅烧温度参数（350℃、450℃、550℃、650℃、750℃），研究了氧空位缺陷对ZnO纳米墙及杂质缺陷对石墨烯的影响。随着煅烧温度的升高，氧空位浓度峰值从45增大到100。同时，随着还原温度的升高（350、450、550、650、750℃）, 还原石墨烯ID/IG的值均变大，表明杂质缺陷度增加。这是因为氧化石墨稀薄膜高温真空还原过程中发生了脱氧还原反应,薄膜上的含氧官能团以CO2和H2O等小分子除去,使得氧化石墨稀的sp2结构得以恢复。同时含氧官能团的消失导致薄膜表面出现空缺。.3）利用原位生长的方法在还原石墨烯薄膜上构筑了ZnO纳米墙。在最佳工作温度175℃下，ZnO纳米墙/石墨烯异质结对50ppmNO2的最大灵敏度高达7.72。与纯ZnO纳米墙相比，灵敏度降低，说明ZnO与还原石墨烯的缺陷作用表现为拮抗效应。与还原石墨烯相比，气敏特性完全发生变化，从p型变成了n型，而且气敏性能得到了很大的提高，由此两种材料的缺陷表现为协同作用。