LiTaO3热释电甚长波红外探测器纳米结构NiCr吸收层的制备及特性研究

Infrared absorber, as one of the most important structures in LiTaO3 based Infrared pyroelectric detectors, became a key factor that has limited the detection of devices in very long wavelength. There are some potential issues of the common used absorbers, including low absorption efficiency, complicated fabrication process and high cost, et al. In this work, based on the pulsed magnetron sputtering technology, the multi-layers of NiCr with graded refractive index and black metal comparable NiCr are investigated, working as the broadband absorber and the selective absorbers respectively. The detectors coated with these nanostructured thin film absorbers consisting the same material as the top electrodes will have the benefits of high absorption efficiency, low cost, easy-done fabrication, et al. Theoretically, the optical model for the multi-layers with graded refractive index was explored, aiming to understand the relationships between the refractive index of each layer, surface morphology, complex dielectric permittivity, film thickness and the optical characteristic of the absorber. Moreover, the experimental and theoretical optimization of thickness was studied to increase the absorption coefficient of the new structure (thin film--λ/4 resonant cavity) in the wavelength range of 14μm-16μm. These novel nanostructured NiCr are very suitable for the key absorber of LiTaO3 pyroelectric detectors, which meets the demand of enhancing the performance of domestic satellite-borne pyroelectric detectors in 14-16µm. Meanwhile, the absorbers we presented in this work will provide technological basis for the preparation of the detector.

红外吸收层作为影响器件吸收特性的重要材料，已成为制约LiTaO3热释电甚长波红外探测器性能提高的关键因素。为改善现有的红外吸收材料在性能、制备工艺和成本等方面的不足，本项目拟采用脉冲磁控溅射技术，制备具有波段选择性的折射率渐变型NiCr吸收材料和宽光谱良好吸收特性的类黑金NiCr吸收材料。所制备材料具有电极和吸收层双重作用，不仅提高了吸收性能，而且可简化工艺，降低成本。同时，建立红外吸收模型，研究吸收材料的折射率、复介电常数、厚度、微观结构与吸收层光学特性的数学关系，在吸收机理的理论研究方面取得突破。此外，本项目亦将对一种由超薄NiCr材料和λ/4真空谐振腔所构成的新型吸收结构的设计与制备展开研究，从理论计算和实验研究两个方面优化NiCr薄膜厚度，实现吸收层在甚长红外波段的选择性吸收。以上研究将解决我国星载热释电探测器对甚长波红外探测的迫切需求，同时为探测器研制提供技术基础。

根据项目主要研究内容，本项目完成情况概述如下：1、完成了LiTaO3热释电探测器吸收薄膜的制备工艺及特性研究。（1）完成了纳米结构NiCr吸收层的设计和制备。基于气压、电流和温度参数，设计正交实验组合沉积薄膜，实现NiCr单层薄膜及渐变型多层薄膜的制备。分析薄膜的微观结构及纵向断面，并对红外吸收性能进行优化。（2）完成超薄NiCr选择性吸收层的制备。改变NiCr薄膜厚度进而实现甚长波红外和太赫兹辐射的吸收最大化。采用化学腐蚀工艺对薄膜进行处理，研究发现处理后的NiCr薄膜表面呈现粗糙化，明显增大了有效吸收面积，进而达到增强吸收的效果。2、完成了LiTaO3热释电探测单元吸收膜系光学模型的构建。通过调节金属吸收薄膜的电导率和厚度（方阻）优化膜系的辐射吸收率。利用Essential Macleod光学薄膜仿真分析红外吸收膜对热释电探测器红外辐射吸收性能的影响。通过控制变量法改变吸收膜系中各膜层厚度，仿真器件辐照吸收，得到最优化热释电探测器吸收膜系条件。为研制高灵敏度、响应迅速的LiTaO3热释电探测器提供重要的理论基础及实验依据。. 项目基本完成了研究目标：研制了LiTaO3热释电探测器吸收薄膜并应用于单元器件，达到甚长波红外增强吸收的效果；发表学术论文10篇，其中SCI论文8篇；申请发明专利6项，授权1项；参加国际会议3次并做分会特邀报告1次；培养博士研究生1名，硕士研究生2名。