C. Charitidis et al., A comparative study of the nanoscratching behavior of amorphous carbon films grown under various deposition conditions, SURF COAT, 125(1-3), 2000, pp. 201-206
Two types of amorphous carbon (a-C) films: one series with a layered struct
ure (sequence of soft/hard carbon layers) resulting in thick, stable and sp
(3) rich films, and another series of monolithic films rich in sp(2), were
deposited on Si substrates by magnetron sputtering and were investigated wi
th respect to their nanoscratching behavior. The main purposes of this work
are to investigate the scratch performance of a-C films developed in layer
ed structure and to compare this with the films rich in sp(2) content. Ultr
alow load scratch tests were performed in the load range from 2 to 20 mN to
explore the deformation mechanisms of such thin films and their adhesion t
o the substrate. Below 5 mN, the scratches on layered structure films exhib
it an almost full elastic response while on films rich in sp(2) content sho
w massive brittle fragmentation. At 20 mN, the scratches on the former film
s reveal some areas which are completely elastic and some areas which were
typical of a buckle failure. These areas may correspond to hard and soft ca
rbon layers, respectively. The coefficient of friction varied from similar
to 0.2 to similar to 0.3, depending on the maximum normal load and being lo
wer for films of the first type. Scratch testing results have shown that la
yered structured films are resistant to plastic deformation during contact
and, together with the stability of the thick layered films, support their
potential for protective overcoats. (C) 2000 Elsevier Science S.A. All righ
ts reserved.