摘要
21世纪以来,扫描探针显微镜(Scanning Probe Microscope,简称SPM)已经成为纳米检测与加工不可缺少的研究仪器。尤其是原子力显微镜(AFM)凭借其原子量级(0.1nm)的精度,在材料科学、生物医学、纳米机电以及微纳加工领域得到了广泛的应用。随着纳米技术的迅速发展以及在纳米检测与加工领域中的深入应用,原子力显微镜技术自身也得到了很大的发展。重庆大学恒瑞纳米技术工作站在现有的IPC-208B型原子力显微镜系统的基础上,不断优化原子力显微镜系统的性能,拓展其应用,并致力于研究开发多工作模式的原子力显微镜。本论文在重庆市科委自然科学基金项目和重庆大学自然科学青年基金项目的资助下,开展了IPC-208B型原子力显微镜系统性能改进、最新实验应用及其压电微悬臂的研究,主要做了以下几个方面的研究工作:
①系统研究以AFM为主的SPM的工作原理、发展概况以及应用情况,详细论述了压电微悬臂的理论和国内外应用发展,重点论述了压电微悬臂在AFM系统中的研究现状。
②介绍实验室近几年在IPC-208B型原子力显微镜系统改进及其最新应用实验方面的工作。系统介绍AFM.IPC-208B型机系统组成,重点介绍显微镜镜体中的步进电机、压电陶瓷、微悬臂、变速系统;改进方面在AFM系统配备了AFM微悬臂调节装置,微悬臂调节机构采用可拆卸式的装置,兼顾了AFM系统功能与STM系统功能,提高了仪器的应用价值。为微悬臂和探针增设探针调节监测装置(2D调节),增强调整的准确性,提高调整效率,避免撞针情况的发生,提高微悬臂的可操作性;选择压电陶瓷扫描器进行下扫描设置,使扫描范围由原来的1000×1000 nm2扩大为10×10μm2,实现大范围扫描;详细论述该系统在微加工、生物医药样品表征、铁磁和铁电材料表征和高分子聚合物纤维材料表征方面的最新的应用进展。
③对AFM系统的压电微悬臂进行设计。根据微悬臂形变与位移传感原理,在AFM压电微悬臂设计原理、讨论其工作模式原理的基础上,给出完整的压电微悬臂结构及系统设计,提出硅底+电极+压电薄膜+电极四层结构;分析对比PZT与ZnO两种压电材料的特点,并分析压电微悬臂感应和执行两种工作方式;研究了微悬臂及其探针的加工工艺;分析压电微悬臂的特点,在与其他方式微悬臂的进行对比分析的基础上探讨压电微悬臂在AFM中的应用前景。
④对AFM压电微悬臂进行有限元分析及ANSYS仿真。根据有限元和ANSYS仿真原理,按照原子力显微镜工作环境和要求,采用有限元方法建立微悬臂模型,采用ANSYS软件对模型进行静力分析求解得到压电分析结果:电压随作用力或位移的变化关系,具有较好的线性度。深入分析模型中的各个参数:长度、宽度、厚度等对电压产生的影响,得到3阶模态振动图及固有频率模态分析结果,并讨论不同尺寸参数对模态频率的影响;分析不同探针位置对模态频率和灵敏度的影响,并对是否考虑延伸端进行性能对比分析;采用电压/位移(△U/△D)对模型的灵敏度进行标度,做各尺寸参数对灵敏度的影响分析;总结仿真分析结果,综合考虑压电微悬臂尺寸的影响,优化分析结果:选择微悬臂长度为200μm,宽度为50μm,延伸端长度为20μm,延伸端宽度为10μm,压电层厚度为1μm,硅底厚度为1.5μm,电极厚度为0.2μm时,微悬臂的一阶频率为f=44.972kHz,灵敏度K=1.71mv/nm。按照AFM探针起伏为0—100 nm计算,压电信号变化范围在0—171 mv,为AFM微悬臂的研制提供参考。
Since 21st century, Scanning Probe Microscopes (SPM) has become an indispensable research instrument in nano-testing and processing. In particular, the Atomic Force Microscope (AFM) with its atomic level accuracy (0.1nm) has been widely used in materials science, bio-medicine, nano-electromechanical and Nano/Micro process areas. With the rapid development of nano-technology and in-depth applications in the field of nano-inspection and processing, atomic force microscope technology itself has also got a great development. Chongqing University Heng-Rui Nano-technical workstation try to optimize the system performance and expand its applications on IPC-208B type atomic force microscope, and be committed to research and development of multi-mode atomic force microscope. In this paper, funded by the Natural Science Fund project of Chongqing Science and Technology Commission and Chongqing University Natural Science Youth Fund project, I carried out some study such as system performance improvements of IPC-208B type atomic force microscope, the latest experimental applications and piezoelectric micro-cantilever research. So, my main researches in the following areas:
①Systematic study was carried out on the SPM for AFM-based with working principle, the development and applications, discussed in the theory of piezoelectric micro-cantilever applications and development at home and abroad in detail, with emphasis on the current study of the piezoelectric micro-cantilever applied in AFM system.
②Recent laboratory works were introduced about the IPC-208B type atomic force microscope system improvement and its latest new application experiments. I introduced AFM.IPC-208B-type system components, with emphasis on the lens body with stepper motor, piezoelectric ceramics, micro-cantilever and transmission system. For the improvements on the AFM system equipped with a regulating device for AFM micro-cantilever, which gives attention to STM and AFM, as well as the added conditioning monitoring devices for cantilever - probe, in order to enhance the accuracy of the adjustment, I improve the adjustment efficiency and avoid the firing pin from happening, all this aims to improve the operability of micro-cantilever. I chose a piezoelectric scanner to complete the under scanning setting, so that the scanning range expanded from the original 1000×1000 nm2 to 10×10μm2, achieving a wide scanning range. Detail the latest system applications were shown in micro-processing, bio-medical samples characterization, ferromagnetic and ferroelectric materials, fiber material characterization and polymer characterization.
③Piezoelectric micro-cantilever was designed for AFM system. According to the relation betwween micro-cantilever deformation and its displacement, based on the AFM piezoelectric micro-cantilever design principle and the selected work mode principle, I gave the complete piezoelectric micro-cantilever structure (Si + pole + piezoelectric film+ pole) and system design; analyzed and compared characteristics of the PZT and ZnO piezoelectric materials, and analyzed the two kinds work ways of piezoelectric micro-cantilever sensors and implementation; analyzed the preparation of micro-cantilever and probe; analyzed characteristics of piezoelectric micro-cantilever based on the comparison between micro-cantilever and other methods, in the end, I analyzed the application prospect of piezoelectric micro-cantilever in the AFM .
④Finite element analysis and ANSYS simulation for the AFM piezoelectric micro-cantilever were completed. According to finite element and ANSYS simulation principle, in accordance with atomic force microscope working environment and requirements, I used the finite element method to establish micro-cantilever model, and used ANSYS software to analyze the model and obtained results of the piezoelectric analysis solution: change relationship of voltage with the force or displacement. I analyzed the impact on the voltage of the various model parameters: length, width, thickness and so on, received three first order modal vibration maps and natural frequency modal analysis results, and discussed the different size parameters on the modal frequency of the impact; and I analyzed impact of different probe needle position on the of modal frequency and sensitivity, and made performance comparison analysis whether consider the extending side; using voltage/displacement (△U/△D) the model sensitivity scale, I analyzed the impact of the size parameters on the sensitivity. At last by optimization analysis, the simulation results was shown: when cantilever length is 200μm and its width is 50μm, extended length is 20μm and its width is10μm, piezoelectric film thickness is1μm, Si thickness is 1.5μm, pole thickness is 0.2μm, we got the basal frequency f=44.972kHz, the sensitivity K=1.71mv/nm. According to the of AFM probe wave 0—100 nm,the piezoelectric signal is about 0—171 mv,which is convenient to be identified for AFM system.
引文
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