In-situ nondestructive characterization of the normal spring constant of AFM cantilevers

Abstract

Various applications of scanning force microscopy in nanomechanics demand that the mechanical performance of cantilevers in use, especially their normal stiffness, be quantitatively calibrated. In this paper, a dynamic reference spring (DRS) method based on the micro-opto-electro-mechanical systems nano-force transducer developed in the PTB is proposed, in which the cantilever bending stiffness is now indirectly determined by inspection of the resonance frequency shift of the nano-force transducer before and after contacting the cantilever to be calibrated. In general, only small cantilever deflections will be generated during calibration, and thus the contact force between the cantilever tip of the atom force microscope and the transducer should be small enough and purely nondestructive to the tip. Compared with other quasi-static cantilever calibration methods, the DRS approach allows relatively fast measurements, is insensitive to the long-term noise observed within ordinary measurement environments and therefore is very suitable for in-situ cantilever spring constant calibrations under poor working conditions. A proof-of-principle experiment has verified the feasibility of this method.