Hydrogenated amorphous carbon films (a-C:H) and hydrogenated carbon fi
lms containing as much as 15 at.% nitrogen (a-CNx:H) were synthesised
by a plasma-assisted chemical vapour deposition (PACVD) apparatus. By
changing the gaseous precursor (CH4, C6H12, C6H6, C2H2) the hydrogen c
ontent of the films can be varied between 26 and 58 at.%; serious adhe
sion problems were found when the hydrogen percentage attains the high
est value. Hydrogen-free layers were deposited by magnetron sputtering
in Ar (a-C) and N-2 (a-CNx): nitrogen fractions range from 8 to 28 at
.% and increase when the substrate is closer to the graphite target du
ring deposition. Film hardness was evaluated by nanoindentation in old
er to avoid inflation of the assessed value consequent to the elastic
recovery, which results to be quite large in the examined layers. The
hardness measurements show values up to similar to 30 GPa and point ou
t that both nitrogenation of a-C:H films and deposition by magnetron o
f hydrogen-free a-C layers lead to softer materials (similar to 18 GPa
). Main features of Raman spectra are broad 'G' and 'D' peaks, charact
eristic of DLC layers: correlation between parameters of these peaks i
s discussed. (C) 1998 Elsevier Science S.A.