Dependence of microstructure and nanomechanical properties of amorphous carbon nitride thin films on vacuum annealing

Three kinds of ultrathin amorphous carbon nitride films (alpha -CNx) with d ifferent internal stress were deposited on silicon (111) substrates by an i on beam assisted deposition method. The as-deposited alpha -CNx was post-an nealed to eliminate the internal stress. The microstructure and nanomechani cal properties of both as-deposited and annealed alpha -CNx were studied by using micro Raman spectroscopy, nanoindentation measurement, and nanoscrat ch test in atomic force microscopy. The Raman spectra of as-deposited and a nnealed him show that the ratio of intensities of the D band to G band incr eased after vacuum annealing. Nanoscratch tests showed that the elimination of compressive internal stress due to annealing resulted in reduced scratc h resistance, while elimination of tensile internal stress due to annealing resulted in enhanced scratch resistance. Nanoscratch test results were in good agreement with the results of nanoindentation measurement. Experimenta l results indicate that the effect of internal stress on scratch resistance is stronger than that of microstructure evolution due to post-annealing. N anoscratch tests show that suitable compressive internal stress is benefici al for enhancement of nanoscratch resistance of the thin alpha -CNx film. ( C) 2000 Elsevier Science S.A. All rights reserved.