基于碘化铅厚膜的新型数字平板探测器的材料、器件与工艺研究

Compared with amorphous silicon and amorphous selenium material, the digital X-ray flat panel detector (FPD) based on lead iodide (PbI2) polycrystalline films can obtain higher spatial resolution and quantum detection efficiency. As core of the FPD, controllable growth process for large-size and high-quality PbI2 polycrystalline films and device fabrication technology are keys to ensure the performances of the FPD and the real-time and high-resolution digital image. Based on our previous research, this project is intended to optimize the close-space sublimation technique (CSST) of PbI2 polycrystalline films growth, to improve the electronic properties of PbI2 films and the devices through the research on the surface/interfacial characteristics and the fine processing technologies of the soft crystallized film surface. Through analysis on carrier generation, transmission and recombination mechanisms in photo-conductive layer, the signal readout array device and the multichannel preamplifier circuit will be designed to achieve efficient signal collection, transmission and processing. Furthermore, the interaction mechanisms of the material properties, device structure, electrical systems and exposure parameters towards the FPD’s image performance will be clarified. The tools for multi-pixel information integration and algorithm, and the indicators for image evaluation should be developed to construct the system of the FPD imaging performance evaluation. Ultimately, the clear influence relationship for the FPD performances from various factors will be determined. And by using the optimized PbI2 polycrystalline film growth and device technology, we will fabricate a PbI2-FPD prototype which can obtain clear digital images to meet the actual needs of the research and application of the high-performance FPD device.

相比非晶硅与非晶硒，基于碘化铅(PbI2)多晶膜的数字X射线平板探测器(FPD)具有更高的空间分辨率和探测效率。作为FPD的核心，大尺寸高质量PbI2多晶膜的可控生长及器件化技术，是确保器件性能、获得实时高清晰数字图像的关键。本项目基于前期研究，优化PbI2多晶膜生长的近空间气相沉积技术，研究膜层表面/界面特性及软质结晶膜表面处理技术，改善材料和器件电子学性能；分析膜层内光生载流子产生、传输与复合机制，设计信号读出阵列器件及多路前置放大电路，实现电荷信号高效收集、传输和处理；阐明材料性能、器件结构、电路系统和曝光参数等对成像质量的影响机制，确定多像元信息整合及算法、影像评估参数指标，建立FPD成像性能评价体系。最终，明确影响FPD性能各因素间的关系与规律，采用优化的PbI2多晶膜生长及器件化技术，制作出可获得清晰图像的PbI2-FPD原型，满足高性能平板探测器研究和应用的实际需要。

相比非晶硅与非晶硒，基于碘化铅多晶膜的数字X射线平板探测器(FPD)具有更高的空间分辨率和探测效率。作为FPD的核心，大尺寸高质量多晶膜的可控生长及器件化技术，是确保器件性能、获得实时高清晰数字图像的关键。本项目主要开展碘化铅厚膜生长工艺优化、TFT基板设计与制造、TFT基板上多晶膜沉积、多晶膜表面处理、多路低噪声CSP设计与开发、探测器成像性能评估等内容研究，搭建了碘化铅粉料升华提纯装置，初步实现了单次200g级的粉料提纯，产率~80%；自主设计研制了碘化铅膜层沉积装置，可实现单次最大200mm*200mm膜层的制备，原料利用率大于95%，最高温度650℃，真空度优于1.0*E-4 Pa；阐明了碘化铅晶体的电学性能各项异性，E⊥c结构器件暗电流比E//c器件高约30倍，且E⊥c结构器件的载流子俘获效应（Trapping effect）更为显著，决定了器件响应特性以及高速特性，为平板探测器的碘化铅膜层结构调控提供最直接的指导；提出了碘化铅膜层表面激光重结晶技术与方法。该方法可以在原生膜层或机械抛光处理后的膜层表面直接形成厚度10-20um的重结晶层，且保持与主体膜层一致的物相结构，进一步提高了膜层的致密度、结晶度，提高了后续阻挡层和电极层材料的结合力，改善膜层的界面特性。激光重结晶技术可借助扫描装置，对大面积碘化铅膜层进行快速、可控表面处理，这对于未来产品化具有重要的意义；提出了微束流电子束蒸发法制备高致密度纳米晶碘化铅膜层材料，具备纳米晶尺寸均匀、透光性高、致密度接近晶体密度，大面积尺寸结构均匀性好，可在室温下沉积，以及衬底适应性强的优势，工艺参数可控性强、膜层纯度高、组分损失少，是一种极有产业应用价值的探测器光电转换材料沉积技术。