Abstract: Diamond-Like Carbon films were deposited on Si substrate from the mixture of C₂H₂ and Ar by r.f.-d.c. plasma enhanced chemical vapor deposition. The influence of deposition process
on the density and distribution of void in Diamond-Like Carbon films was systematically studied by low energy positron beam. The results indicate that the density of void
in Si substrate is the highest. A constant distribution of void was observed through the films, the density of void is lower, but the density of void in the surface layer
is higher. The density of void starts to increase near the interface and finally reaches the value of Si substrate. With the increasing of bias, the density of void in the
films and the depth of interface decrease at first, then increase, and then decrease. The density of void in the films increases monotonous with the increasing of
C₂H₂ percentage in the feed gas.

Key words: Diamond-Like Carbon films, defect, low energy positron beam, annihilation