Measurements of elastic properties of ultra-thin diamond-like carbon coatings using atomic force acoustic microscopy

We present a comparative study of the elastic stiffness of ultra-thin (5, 2 0 and 100 nm thick) diamond-like carbon coatings with a sampling depth less than or comparable to the thickness of the coating. The experiments were c onducted using atomic force acoustic microscopy, which is a dynamic operati on mode of the atomic force microscope that permits the measurement of elas tic properties with high spatial resolution. The method is based on the eva luation of the shift of the cantilever resonance frequencies caused by the contact stiffness between the sensor tip and the sample surface. Two sets o f measurements are reported: one in which the silicon sensor tips were empl oyed; and another set in which diamond-coated tips were used. The silicon t ips showed considerable wear during data acquisition. Using the diamond-coa ted tips, however, the wear could be avoided and qualitative measurements o f high stability could be performed, thereby permitting the comparison of c oatings obtained by different deposition techniques. It is also shown how t he obtained results can lead to future quantitative measurements on stiff c oatings. (C) 2001 Elsevier Science B.V. All rights reserved.