Stress generation mechanisms in carbon thin films grown by ion-beam deposition

A three-dimensional molecular dynamics (MD) simulation is performed to study the stress generation mechanisms in carbon thin films grown by ion-beam deposition. The relationship between the kinetic energy of incident ions and the steady-state film stress is established. Examination of the atomic stress and film microstructures reveals that the grown films contain a significant fraction of vacancies, contradicting the presumption of the subplantation model. By taking into account both interstitials and vacancies, an analytical model is developed, in which the formation of the compressive stress is attributed to competing mechanisms between generation and recovery of the defects. This model can satisfactorily explain the numerical observation in which compressive stress prevails in films in the presence of vacancies. The present study provides useful insights into tailoring residual stress to control thin film curvature in microelectromechanical systems (MEMS) by ion-beam machining.