Linearizing the frequency-stiffness relation in contact resonance atomic force microscopy for facilitated mechanical characterization.

To facilitate mechanical characterization by contact resonance atomic force microscopy (CR-AFM), a cantilever that could enable a near linear relation between CR-frequency and contact stiffness is designed. The optimized structure is fabricated through removing a rectangular slot from a conventional cantilever as a prototype, and the dimensions of the removed slot are determined by finite element simulations. We validate the target CR-characteristics on a silicon substrate with circular cavities covered by highly oriented pyrolytic graphite flakes, on which the contact stiffness can be well modeled. Elastic modulus measurements on different materials demonstrate that the linear relation provides a convenient yet accurate way to evaluate sample's elasticity. It could thus bring great convenience to various CR-AFM relevant applications such as mechanical characterization and subsurface nano-imaging. RESEARCH HIGHLIGHTS: A cantilever that could enable a near linear relation between CR-frequency and contact stiffness is designed to facilitate contact resonance atomic force microscopy. The CR-characteristics are verified on a silicon substrate with circular cavities covered by highly oriented pyrolytic graphite flakes. Elastic modulus measurements on different materials demonstrate that the linear relation provides an easy yet accurate way to evaluate sample's elasticity.