Adhesive strength of DLC films prepared by ionization deposition

摘要

Diamond-like carbon (DLC) films are considered to be promising to develop extensively for practical applications owing to their good properties. Improvement of adhesive strength of DLC films to substrates is required to enhance their suitability and reliability. The purpose of this study is to investigate the influence of the preparation conditions of DLC films on the adhesion. DLC films were prepared from benzene gas by the ionization deposition method. Three different anode voltages of 50, 75 and 100 V were applied during deposition. The substrates used were WC-Co, austenitic 18Cr-8Ni stainless steel and Al-Mg alloy. The adhesive strength was measured by a tensile pull-off tester. We examined and discussed the adhesion of DLC films from the viewpoints of the internal stress in the films and the species in plasma during deposition. The main results obtained from this study are as follows: (1) The adhesive strength of DLC films to substrates can be enhanced by controlling the anode voltage. (2) For thicker films, the adhesive strength of DLC films increases with increasing internal stress. (3) At the anode voltage of 50 V, higher adhesive strength of DLC films can be attained than that prepared at other anode voltages, but the internal stress is much higher. It is presumed that DLC films prepared at an anode voltage of 50 V have large amounts of C_2, CH and C_5H_5 fragments against hydrogen in deposited films.