石墨烯集成微结构的高性能太赫兹探测器研究

Terahertz detection based on novel nanomaterials, such as graphene, is a hot topic in the field of terahertz technology. In particular, photothermoelectric devices with asymmetric microstructures constructed by using graphene as the channel material have unique advantages in terms of bandwidth, response speed, operation temperature, integration level and power consumption. However, the existing devices face problems of weak terahertz absorption of graphene, competition between high sensitivity and fast response, and the coexistence of several physical mechanisms in a single device restricting the response performance optimization. This project considers the design, fabrication and terahertz detection mechanism and performance optimization of microscopic asymmetric microstructure graphene devices. We will focus on the investigation on the interaction of terahertz waves with carriers in this kind of devices, make a deep understanding of heat conduction and carrier transport behavior in the graphene-metal contact and the graphene channel under terahertz illumination, and reveal the key physical factors affecting the photothermoelectric effect. We will test and analyze the influence of channel material, device structure, operation environment and excitation condition on the response characteristics. On the basis of these theoretical and experimental investigations in comprehensive and systematic ways, we will optimize the photothermoelectric response performance of the device, and construct a graphene terahertz photothermoelectric array detector prototype with a high sensitivity and a fast response at room temperature, so as to provide a new way for the development of high-performance and practical terahertz detection techniques.

基于石墨烯等新型纳米材料的太赫兹探测技术是当前太赫兹领域的研究热点。特别的，由石墨烯作为沟道材料构建的非对称微结构光热电器件在响应带宽、响应速度、工作温度、集成度、功耗等方面有独特优势，但面临石墨烯对太赫兹波吸收弱、高灵敏与快响应相互竞争、单一器件多种物理机制共存制约响应性能优化等问题。本项目拟选取非对称微结构石墨烯器件的设计、制备及其太赫兹探测机理与性能优化为研究内容，重点探讨太赫兹波与该类器件中载流子的相互作用过程，深刻理解太赫兹场作用下石墨烯-金属接触及石墨烯沟道中的热传导和载流子输运行为，深入挖掘影响光热电效应的关键物理因素，测试分析沟道材料、器件结构、工作环境和激发条件对器件响应特性的影响。在全面系统的理论与实验探究基础上，优化器件的光热电响应性能，构建室温工作、高灵敏、快响应、阵列化的石墨烯太赫兹光热电探测器原型，为发展高性能、实用化的太赫兹探测技术提供新途。

石墨烯的无带隙性质使其非常适合作为太赫兹波段光电探测器的光敏材料，然而石墨烯与太赫兹波相互作用较弱，限制了探测灵敏度。本项目提出将人工微结构与石墨烯集成以开发高性能太赫兹探测器。主要成果如下：研制了超材料吸收体增强的太赫兹石墨烯光热电探测器，揭示了超材料吸收体在激发电磁谐振、形成局域场增强、提高器件吸收率、构建非对称温度场等方面的作用，通过对不同尺寸参数器件、不同偏振入射光等情形的研究验证了器件的响应机理，实现了快响应高灵敏太赫兹探测；研制了波长选择与偏振敏感的超材料-石墨烯单片集成太赫兹探测器，利用超材料光学性质的超高设计自由度以及石墨烯中热载流子辅助光热电效应的超宽谱、电可控特性，在单片结构上集成了太赫兹波的光强探测、波长选择与偏振敏感探测功能，完成了多色成像和偏振分辨成像的实验验证；研制了非对称金属掺杂的微结构石墨烯探测器阵列，采用金属Pd和Ti对石墨烯沟道形成非对称掺杂，同时结合扇形耦合天线增强石墨烯的光热电响应，制备了32×32单元的探测器阵列，经测试，等效噪声功率、响应时间等性能指标满足项目预期要求；利用离子液体-电双层技术对三维石墨烯的热电性能进行了调控，使其Seebeck系数及太赫兹光热电响应均提高了一个数量级，由此构建了p-n结双腔室型离子液体调控的三维石墨烯太赫兹光热电探测器，为石墨烯太赫兹光热电探测器性能的优化调控提供了新途径。项目成果发表在ACS Nano、Advanced Functional Materials、Laser & Photonics Reviews、Advanced Optical Materials、ACS Applied Materials & Interfaces、《科学通报》等刊物，申请发明专利4项，培养博士后2名、博士研究生2名、硕士研究生2名。