支持大范围表面实时搜索及成像的高速原子力显微系统研究

Atomic force microscopy (AFM) is one of the most important methods in micro/nano sensing and detection. However, the low imaging rate has become the bottleneck which limits the traditional AFM in improving the working efficiency and further expanding its application fields. This research proposal aims to develop the high-speed atomic force microscopic system supporting real-time survey and imaging on surface with large scale from three aspects which are the high-speed scanning methods, the laser-tracking optics, feedback-control electronics and algorithm. Firstly, the beam tracking for optical lever detection which is coaxial with the optical microscope will be designed. Next, the scanner for lateral movement of the tip will be developed by combining the resonance-type scanner with the flexure structures. And a compact high-frequency piezo-stack actuator will be employed for the vertical movement of the tip. Following that, the fast feedback-control electronics based on FPGA will be built and the feedback-control algorithm suitable for the regulation of the tip-sample interactions during high-speed scanning will be studied. Then the multi-parameter fitting algorithm will be used to overlap, stitch and register small area scanning images to realize real-time survey and imaging on the sample surface with large scale. Finally, typical micro/nano scale dynamic process will be chosen for the real-time observation. The morphological changes of the test sample and the underlying reasons will also be discussed. This research proposal is of great significance to expand the application fields of the traditional AFM and promote the techniques and methods of the research on micro/nano characterization in our country to reach the international advanced level.

原子力显微术是微纳传感与检测领域的重要手段之一，但成像速率低已成为制约传统原子力显微术提高工作效率、拓展应用范围的瓶颈。本课题拟从成像系统的高速扫描方法、光杠杆跟踪光路、反馈控制电子学系统及算法几方面入手，开展支持大范围表面实时搜索及成像的高速原子力显微系统研究。构建与光学显微镜共轴的光杠杆-光束跟踪系统；通过共振式扫描器与柔性机构相结合的方法设计横向扫描器，并利用小体积高频压电陶瓷堆作为纵向扫描器；搭建基于FPGA的快速反馈控制电子学系统，部署高速扫描成像中调控针尖-样品相互作用的反馈控制算法；利用多参数拟合等算法对小区域高速扫描图像进行层叠、拼接与配准，实现大范围样品表面实时搜索及成像；对典型的微纳米尺度动态过程进行观测并探讨样品形态变化的成因。本课题的研究将对于拓展传统原子力显微术的应用领域，推动我国微纳表征技术与方法研究达到国际先进水平具有重要意义。

原子力显微术是微纳传感与表征领域的重要手段之一，在物理、材料、生物以及工业测试等方面都具有广泛的应用前景。近年来，原子力显微术衍生发展出了一系列优势显著的功能化探测模式和新技术，例如：高速扫描、多频探测等新成像模式。原子力显微镜仪器也在更高精度、更高分辨率、更快速度、更多功能等方面都提出了更高的要求。本项目针对高速原子力显微镜仪器中关键部件进行了优化设计；提出了一种扫描成像及可重触发有限脉冲序列产生及同步方法，基于该方法可实现扫描成像系统的同步拓展；开发了一种基于网络的分布式数据采集软件；搭建了基于PXIe控制器的高性能数据采集系统，每通道可以最高250 MSa/s的采样率对测量信号进行连续采集；研制了一种基于FPGA的高性能数字锁相放大模块，可在高达50 MHz的解调频率下实现微弱信号的锁相放大功能；提出了一种基于机器学习的信号异常检测方法，对采集信号预处理并提升信号采集的准确度；针对动态显微图像目标跟踪中，目标易丢失且背景噪声较大的问题，提出了一种利用特征点跟踪算法逐帧跟踪运动颗粒的方法。相关成果为进一步推动原子力显微成像仪器的研发及应用具有重要意义。