Mode-synthesizing atomic force microscopy for volume characterization of mixed metal nanoparticles.

Atomic force microscopy (AFM) and other techniques derived from AFM have revolutionized the understanding of materials and biology at the nanoscale, but mostly provide surface properties. The observation of subsurface nanoscale features and properties remains a great challenge in nanometrology. The operating principle of the mode-synthesizing AFM (MSAFM) is based on the interaction of two ultrasonic waves, one launched by the AFM probe f(p), a second launched by the sample f(s), and their resulting nonlinear frequency mixing. Recent developments highlighted the need for quantitative correlation between the role of the frequency actuation of the probe f(p) and the sample f(s). Here we present the great potential of MSAFM for advanced volume characterization of metallic nanoparticles presenting a multilayered structure composed of a nickel core surrounded by a gold envelope.