A Control-Based Approach to Accurate Nanoindentation Quantification in Broadband Nanomechanical Measurement Using Scanning Probe Microscope

This paper presents a control-based approach to accurately quantify the indentation in broadband nanomechanical property measurements using scanning probe microscope (SPM). Accurate indentation measurement is essential to probe-based material property characterization as the force exerted and the indentation generated are the two most important physical variables measured in the process. Large measurement errors, however, occur when the measurement frequency range becomes large (i.e., broadband). Such errors result from the inability of the conventional method to account for the difference between the SPM z-axis piezo actuator displacement and the vertical displacement of the cantilever at its fixed end, and the lateral-vertical coupling-caused cantilever motion when the measurement frequency range increases. A control-based approach is presented to address these limits of the conventional method. The proposed approach is demonstrated through experiments to measure the viscoelastic properties of a Polydimethylsiloxane (PDMS) sample over a broad-frequency range.