Cantilever optimization for applications in enhanced harmonic atomic force microscopy

- A cantilever was optimized for enhanced AFM harmonic imaging.
- Optimizations were carried out to satisfy multi-objectives.
- Image contrast to material difference was improved at least 3 times.
- Experiments and analysis ascertain the improvement of sensitivity.

Structural design and optimization of atomic force microscopy (AFM) cantilevers were performed with multi-objectives to tailor one or more higher-order resonance frequencies to be integer multiples of the fundamental one and to keep the minimum change of stiffness. The tuning of frequency properties was achieved by altering mass distribution of the cantilever via cutting a rectangular slot. Rayleigh-Ritz method and finite element analysis were incorporated in the optimizations of slot dimension and position. The determined structure was fabricated on a conventional AFM cantilever by using focused ion beam etching. Higher harmonic imaging with the micromachined cantilever on a two-component polymer blend was subsequently performed. Experiments and theoretical simulations demonstrated that the harmonic amplitude contrast was improved up to at least 3 times. The enhancement of harmonic signals can benefit the discrimination of materials with different elastic properties.