The importance of rare events in thin film deposition: a molecular dynamics study of tetrahedral amorphous carbon

Abstract

The transition of diamond-like materials from an sp³ to sp² rich state is of particular interest because of the desirable properties of tetrahedral amorphous carbon (ta-C). Previous works indicate that infrequent processes may dominate this transition, but simulation of these processes presents significant difficulties, since the infrequent processes are activated on the millisecond scale. In this molecular dynamics study the environment dependent interaction potential is used to simulate the thin film deposition of ta-C. Infrequent processes occurring between energetic impacts were activated on the picosecond scale using elevated temperatures. The simulations reveal an abrupt transition in which the ta-C films transform into graphite-like sheets. A similar transformation, albeit at much higher temperatures, is also observed when the films are heated without energetic impacts. These results are found to be in good agreement with published experimental data.

Keywords:

• Molecular dynamics
• Tetrahedral amorphous carbon
• Infrequent events
• Thin film deposition