DIFFICULTIES IN ESTIMATING THE RHEOLOGICAL PROPERTIES OF DIAMOND-LIKE FILMS BY MEANS OF NANOINDENTATION TESTS

A depth-sensing indentation test on the nanometre scale was used for studying the rheological properties of several types of diamond and diamond-like carbon (DLC) coatings. Quantitative values of the hardness have been extracted from curves of the plastic depth of indentation vs. the load, even on very hard crystalline and amorphous diamond films. Moreover the test provided reproducible information about the adhesion of these films to their substrates. Any cracking at the interface was detected as a discontinuity in the variation of depth d with the ramped load L, and it occurred for a well-defined pair of values (L, d). Films of amorphous diamond obtained by ion beam or laser plasma implantations were found to be as hard as crystalline diamond and much more adherent to silicon than other DLC films are.