Quantitative Contact Spectroscopy by Atomic-Force Acoustic Microscopy

Conclusion

The AFAM technique is a sensitive method for the quantitative measurement of local elasticity, here on a scale of 200 nm. On a silicon single-crystal oriented in 〈100〉 direction, the results for the measured Young’s modulus are in good agreement with the known value, In nanoscaled thin films of ferrites with a grain size of about 70 nm, we were able to detect the difference in the elasticity caused by the deviation from the stoichiometry. With the AFAM technique, surfaces with a large enough difference in elastic modulus can be distinguished reliably. However, for reproducible quantitative measurements in the linear as well as in the nonlinear force range, the problem of sensor tip stability is not yet solved. This could be made possible either by using more stable diamond tips with larger radii or by working in a controlled environment to reduce adhesion by meniscus forces. Modeling the nonlinear behavior of the contact resonances, as for example the hysteresis, would allow one to gain further information about the interaction forces. Finally, there are two techniques to image ferroelectric domains in PZT material. They can be made visible by anisotropic etching. In that case one can only image a frozen-in state of the surface. A life image, however, can be obtained by the inverse piezoelectric effect allowing one to examine the domain dynamics.