Effects of melting temperature on mechanical properties and bond structures of DLC Films: A molecular dynamic simulation

Melting temperature was the main factor in the preparation process of DLC(Diamond Like Carbon) films. MD (Molecular Dynamics) method was used to simulate the preparation process of DLC films based on the Tersoff potential. The mechanical response and atomic bonding structure of DLC films during nano indentation process under different melting temperatures were simulated and analyzed. Then studied the atomic displacement gradient and crystal coordination number to elucidate the film forming mechanism of DLC films. The results shows that: In the temperature range of 5 000 K similar to 8 000 K, the higher the melting temperature, the lower the hardness and the elastic modulus of DLC films, as well as the larger the residual depth in nano indentation process. That is mainly related to the content of C-sp(3) and C-sp(2) hybridized in DLC films. When the melting temperature was less than 6 000 K, the percentage content of (sp(2)+sp(1)) hybrid in the system was 0, the hardness was 56.25 GPa, the elastic modulus was 861.9 GPa. When the melting temperature was rise to 8 000 K, a large number of C-sp(3) hybrid atoms would be transformed C-sp(2) to and C-sp(1) during the process of melting, cooling and relaxation stages. While the percentage content of (sp(2)+sp(1)) hybrid increased to 51.6%, the hardness was 39.6 GPa, the elastic modulus was 482.2 GPa, the mechanical properties of DLC films close to graphite.