Tourek Christopher J, Sundararajan Sriram
Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA.
Rev Sci Instrum. 2010 Jul;81(7):073711. doi: 10.1063/1.3459886.
Force studies using atomic force microscopy generally require knowledge of the cantilever spring constants and the optical lever sensitivity. The traditional method of evaluating the optical lever sensitivity by pressing the tip against a hard surface can damage the tip, especially sharp ones. Here a method is shown to calculate the sensitivity without having to bring the tip into contact. Instead a sharpened tungsten wire is used to cause a point contact directly onto the cantilever and cause cantilever bending. Using beam theory, the sensitivity thus found can be converted to the equivalent sensitivity that would be obtained using the tip location. A comparison is presented between sensitivity values obtained from the conventional tip contact method and those derived from the wire-based technique for a range of cantilevers in air. It was found that the difference between the calculated sensitivity from the wire-based technique and the sensitivity obtained conventionally was less than 12%. These measurements indicate the presented method offers a simple alternative approach to obtain optical lever sensitivity without compromising the tip shape.
使用原子力显微镜进行力的研究通常需要了解悬臂梁的弹簧常数和光杠杆灵敏度。通过将探针压在坚硬表面上来评估光杠杆灵敏度的传统方法可能会损坏探针，尤其是尖锐的探针。本文展示了一种无需使探针接触就能计算灵敏度的方法。相反，使用一根尖锐的钨丝直接在悬臂梁上造成点接触并使悬臂梁弯曲。利用梁理论，由此得到的灵敏度可以转换为使用探针位置时所获得的等效灵敏度。针对一系列在空气中的悬臂梁，给出了从传统探针接触法获得的灵敏度值与从基于钨丝的技术得出的灵敏度值之间的比较。结果发现，基于钨丝的技术计算出的灵敏度与传统方法获得的灵敏度之间的差异小于12%。这些测量结果表明，所提出的方法提供了一种简单的替代方法来获得光杠杆灵敏度，而不会损害探针形状。
