Application of optical force measurement to mode characterization of atomic force microscopy nanomachining

Abstract

Atomic force microscopy is often used not only to acquire the sample surface topography at the subnanometer scale but also to measure forces on the surface during imaging. This study aims to develop a practical measurement scheme of the actual scratching forces exerted during atomic force microscopy nanoscratching using a simple optical microscope setup. The measurement results are utilized to analyze the mode characteristics of atomic force microscopy nanomachining. Unlike typical atomic force microscopy force measurement methods using position-sensitive detector signal analysis, the optically measured atomic force microscopy cantilever deformation data using varying input (normal) forces along with information on the cantilever stiffness were used to estimate the components of the actual force exerted during nanomachining without using complex data interpolation methods. Scratching experiments were performed on Si(100) workpieces, and the estimated real force values were compared with the experimental data from atomic force microscopy nanomachining for each input force and corresponding scratch depth. Frictional coefficients and in-process acoustic emission monitoring results were also used to conduct an in-depth analysis of the actual force results. It is shown that the estimation results are meaningfully close to both the theoretical evaluations and the scratching experimental data as the scratch depth changes. Moreover, the force data are shown to have the ability to detect mode transitions such as the elastic-plastic and the plowing-cutting transitions during nanomachining, which validates the utility of this approach.