Time-dependent deformation behavior of amorphous nitrogen-containing carbon films

An indentation creep test has been performed to investigate the nanostructu re changes in nitrogen-containing carbon films showing a relatively high ha rdness value. The time-dependent indentation depth of the hard films indica tes a monatomic increase at the initial stage of the creep procedure and th ereafter, remains constant. Using the results of the slope of the time-disp lacement relation at the initial stage of the creep procedure, the strain r ate sensitivity exponent m is obtained. Several experiments were conducted under various applied forces, ranging from 20 to 600 mN, to confirm the dif ferences in the viscous How characteristics of samples with various nitroge n contents. The results revealed that viscous flow of the sample began only when the applied force was increased beyond a critical value. The critical loading force rapidly dropped with increasing, extent of nitrogen-carbon b onding in the film.