Research on atomic force microscope using photothermal vibration and optical detection of micro cantilever

本研究发展了一种新型的基于光热振动力敏悬臂梁的原子力显微镜。通过在样品上扫描细针尖以保持施加到针尖的力导数来获得样品的表面轮廓。力的导数是通过使用锁定放大器，其参考频率是光热振动的悬臂梁。在本研究项目中，我们取得了如下成果：1）采用激光辅助刻蚀技术制备了悬臂梁; 2）构建了原子力显微镜（AFM）系统。三脚架扫描器组成的堆叠PZT被用来作为一个精细的定位器，和机动千分尺也被用来作为一个粗略的定位器。采用He-Ne激光器，用光偏转法测量了调幅半导体激光器引起的悬臂梁振动。该系统安装在隔振台上。3）利用原子力显微镜对亚微米级左右已知结构的样品进行了观察，以估算原子力显微镜的横向和纵向分辨率。结果，AFM的横向和纵向分辨率分别为2和50 nm。

In this research, a new atomic force microscope based on a photothermal vibration of force sensing cantilever was developed. A surface profile of sample is obtained by scanning the fine needle tip over the sample so as to maintain a force derivative applied to the tip. The force derivative is detected by the use of loCK-in amplifier of which reference frequency is that of photothermal vibration of the cantilever. In the term of research project, we have obtained the results as follow.1) The cantilever was fabricated by a laser assisted etching.2) The atomic force microscope (AFM) system was constructed. The tripod scanner composed of stacking PZTs is used as a fine positioner, and the motorized micrometer is also used as a coarse positioner. The vibration of the cantilever caused by a amplitude modulated laser diode was detected by the optical deflection method with He-Ne laser. The system was mounted on the vibration isolation table. The feedback circuit including the interface of personal computer was constructed.3) In order to estimate the lateral and vertical resolution of the AFM, the samples of known structure around the size of submicrometer was observed by the AFM. As a result the lateral and vertical resolution of the AFM was 2 and 50 nm, respectively.