AFM-Based Nanomechanics

Our goal is to provide tools for nanotechnology research and development that rapidly and nondestructively map the nanoscale mechanical properties of new materials and devices. Measuring localized variations in properties not only yields valuable information on material homogeneity and manufacturability, but also enables early identification of subsurface defects. Our methods also provide size-appropriate data critical for the predictive modeling of device reliability and performance.

The atomic force microscope (AFM) offers many advantages for nanoscale measurements. Most notably, the small radius of the AFM tip (~5 nm to 50 nm) enables true nanoscale spatial resolution. Several AFM methods have been developed to assess mechanical properties, but most can only produce qualitative images. In contrast, contact-resonance force microscopy (CR-FM) enables quantitative mechanical-property mapping. CR-FM involves vibrating the AFM cantilever while its tip is in contact with a sample. In this way, the resonant modes of the cantilever—the “contact resonances”— are excited. From measurements of the contact-resonance frequencies, information is obtained about the interaction forces between the tip and the sample (e.g., contact stiffness). Models for the tip-sample contact mechanics are then used to relate the contact stiffness to mechanical properties such as elastic modulus.