Dynamic characterization of AFM probes by laser Doppler vibrometry and stroboscopic holographic methodologies

In atomic probe microscopy, micro-probes of various sizes, geometries, and materials are used to define the interface between the samples under investigation and the measuring detectors and instrumentation. Therefore, measuring resolution in atomic probe microscopy is highly dependent on the transfer function characterizing the micro-probes used. In this paper, characterization of the dynamic transfer function of specific micro-cantilever probes used in an Atomic Force Microscope (AFM) operating in the tapping mode is presented. Characterization is based on the combined application of laser Doppler vibrometry (LDV) and real-time stroboscopic optoelectronic holographic microscopy (OEHM) methodologies. LDV is used for the rapid measurement of the frequency response of the probes due to an excitation function containing multiple frequency components. Data obtained from the measured frequency response is used to identify the principal harmonics. In order to identify mode shapes corresponding to the harmonics, full-field of view OEHM is applied. This is accomplished by measurements of motion at various points on the excitation curve surrounding the identified harmonics. It is shown that the combined application of LDV and OEHM enables the high-resolution characterization of mode shapes of vibration, damping characteristics, as well as transient response of the micro-cantilever probes. Such characterization is necessary in high-resolution AFM measurements.