Relationship between mechanical properties and chemical groups in a-C:F films prepared by RF unbalanced magnetron sputter deposition

a-C:F films were prepared by RF unbalanced magnetron sputter deposition on Si substrates. The modulus and hardness of the films and their relationship with chemical groups in the films were investigated. The results show that the modulus and hardness of the deposited films are not only determined by the nature of cross-link C-C network, but also affected by the fluorocarbon groups. The C-C network of the films is composed of sp² cluster, thus the modulus and hardness of films are close to those of polycrystalline graphite. Compared with other fluorocarbon groups existing in the films, the effect of -(CF-CF)_n- group on the modulus and hardness of the films is much higher. With increasing of -(CF-CF)_n- group proportion, modulus and hardness of the films linearly decrease.