The deposition and study of hard carbon films

Abstract

Carbon films have been deposited by rf plasma decomposition of methane at 50–1400 V negative bias and 1.3×10−3–1.3×10−1 mbar pressure. Hardness, internal stress, density, hydrogen content, and infrared absorption depending on the preparation parameters have been measured. From the IR measurements the ratio of sp3 to sp2 bonds was calculated and the total amount of hydrogen in the films was determined by elastic recoil detection (0.5>H/C>0.15). We found in the range of bias voltages 0<‖−VB ‖<100 V polymerlike films, in the range 100 V<‖−VB ‖<600 V diamondlike hard carbon films with high internal stress, and in the range 600<‖−VB ‖<1400 V graphitelike soft films with low stress. The density of the diamondlike films was about 2 g/cm3 and of the graphitelike films about 1.4 g/cm3. The microhardness seems to be correlated to the internal mechanical stress.