基于石墨烯纳米条纹垂直结构器件及其在磁场作用下的气敏特性研究

Graphene has been considered as one of the ideal sensing materials due to its excellent properties. However, adhesion and absorption take place usually as the gas molecules get close to the surface of graphene sheets, resulting in the extension of sensing and recovery periods of common graphene gas sensors, which have been widely studied with the current parallel with plane geometry. Hence, the objetive of this project is to fabricate a novel gas sensor based on graphene nano-stripe stacks with current perpendicular to plane geometry under magnetic fields. The graphene, which is prepared by chemical vapor deposition method, can be transferred to the substrate with metal electrode, the stacks can be formed during this repeated process. By the combination of 'lift-off' process and O2 plasma eching technique, the device based on graphene nano-stripe stacks with current perpendicular to plane geometry can be finally fabricated. Since both surfaces of graphene stacks are covered with metal electrodes, and the analyte molecules can only be absorbed on the side boundary of the graphene nanostripe stacks. As the size of the distance between layer and layer get close with the mean free path of gas molecules, gas molecules can interact with the boundary area completely, as a result, excllent sensing properties of the device can be achieved (the response time can reach second level). Meanwhile, the design of nano-stripe structures can be benefit for the increase of exposure area. Furthermore, magetic fields can be applied, in order to partially shift the charge carriers to the boundary, leading to complete interaction of carriers and gas molecules, and consequently, the sensing performance of the device can be further improved (to reach ppt level). Based on the studies mentioned above, the novel gas sensing devices based on the graphene nanostrip stacks with current perpendicular to plane geometry under magnetic fields, with special micro/nano structures and high performance, can be fabricated. The gas sensing properties of the resultant devices with different micro/nano structures under magnetic fields will be studied as well, in order to find the optimum structures of the device and consequently develop the sensing mechanism of the resultant high performance gas sensing device.

石墨烯以其优异性能成为制作气体传感器的理想材料之一，但是，气体分子在石墨烯表面易发生粘滞和吸附，石墨烯平面方向传输的载流子与气体分子作用迟滞而导致目前普遍研究的石墨烯传感器存在响应和恢复变慢的问题。本项目旨在研究基于磁场调制的石墨烯纳米条纹垂直结构器件结构调控的关键问题，通过探索研究化学气相沉积生长石墨烯参数、转移工艺参数及微加工工艺参数，实现具有以下独特设计的器件的可控构建：（1）垂直结构（载流子垂直于石墨烯平面传输），石墨烯上下表面均覆盖有金属电极，被测气体仅与侧壁边界处碳原子充分接触，从而实现器件的秒级快速响应；（2）纳米条纹结构，可大幅提高器件与气体的接触面积；（3）外加磁场调制，使器件中载流子向边界偏移，可实现载流子与气体分子充分作用。研究优化器件传感结构和制作技术，实现超灵敏气体检测（达万亿分之一（ppt）量级），探讨此结构器件的气敏机制，建立超灵敏纳米传感器的知识和技术基础。

石墨烯以其优异性能成为制作气体传感器的理想材料之一，但是，气体分子在石墨烯表面易发生粘滞和吸附，石墨烯平面方向传输的载流子与气体分子作用迟滞而导致目前普遍研究的石墨烯传感器存在响应和恢复变慢的问题。本项目创新性地提出和研究了用于痕量气体检测的还原氧化石墨烯（RGO）三维网络微纳垂直结构气敏传感器。项目针对碳纳米材料气体传感器存在的若干关键的科学技术问题有待更深入地研究：（a）纳米材料三大效应需要加以利用；（b）跨尺度微型化，现有的单一微米加工技术工艺难以满足微型化器件进一步发展的需求；（c）高质量碳纳米材料无法实现宏量制备；（d）存在批量生产和实用化的稳定性难题；（e）新型高性能器件的纳米结构设计和性能研究有待深入，创新性地以天然鳞片状石墨作为原料，以化学氧化剥离法制备得到的氧化石墨烯（GO）作为前驱体，利用GO的自组装特性，来构筑由片层堆砌形成的微纳结构；筛选出合适的有机小分子来实现GO的还原及表面接枝，利用有机分子链段上独特的功能基团来实现RGO对气体分子的高灵敏选择性响应特性；利用Fenton试剂产生的羟基自由基来刻蚀GO片得到多孔GO片，并以此为单元构筑亚微米级别的RGO三维网络微纳垂直结构气体传感器，实现其对气体分子的高灵敏响应；并由高分子模板调控作用形成多孔GO三维网络微纳结构，原位还原去除高分子模板后，得到了RGO三维网络垂直结构气敏元件。利用RGO表面及界面结构效应，来研究揭示RGO与气体分子的相互作用规律，并优化其垂直三维结构，成功实现了RGO三维网络垂直结构对气体分子的快速高灵敏响应，该系列工作为高灵敏气体传感器的研究及开发奠定了丰富的理论基础。外加磁场调制研究结果表明，采用剥离法得到的石墨烯对外加磁场具有很好的增强响应效应，而磁场对还原氧化石墨烯薄膜的调制影响不大。