Mapping of surface local elastic constant using Atomic Force Acoustic   Microscopy
  We report a systematic study to determine local elastic properties of surfaces combining atomic force microscope (AFM) with acoustic waves which is known as atomic force acoustic microscopy - AFAM. We describe the methodology of AFAM in detail and interpret the measurement using simple arguments and other complementary measurements using AFM.We have used a few selected samples to elucidate the capability of the AFAM technique to map the local elastic constant of the sample surface. Using the force-distance measurement and the change in the frequency of resonance peak at various regions we quantitatively determine the change in the local stiffness (elastic constant) of the sample surface. We have also shown that AFAM technique can be used to get a better surface image contrast where contact mode AFM fails. 
S. Banerjee, N. Gayathri, S. R. Shannigrahi, S. Dash, A. K. Tyagi and   B. Raj