Dynamical characterization of micro cantilevers by different excitation methods in dynamic atomic force microscopy.

An atomic force microscopy experimental setup was modified to analyze the differences between the piezoelectric excitation and the photothermal excitation (PTE) for three types of cantilevers, including two aluminum coated cantilevers and one uncoated single-crystalline silicon cantilever. The results show the PTE is a direct and localized excitation method to yield smooth and clean frequency spectra representing only the dynamics of the cantilever without the coupling with mechanical components. The cantilever can be easily excited for a high and controllable amplitude by the PTE method as compared to the piezoelectric excitation. The 1st and 2nd order flexural vibration amplitudes of the coated cantilever are easily and efficiently excited by the PTE method, mainly due to the bimetallic effect and a high photothermal efficiency. The energy conversion and absorption efficiency comparison has been analyzed for different cantilevers by the PTE method. The spurious effects can be avoided by the PTE method which clearly reflects dynamic characteristics of the cantilever, and the scanning image quality can be improved.