Enhanced adhesion of diamond-like carbon films with a composition-graded intermediate layer

Abstract

Adherent diamond-like carbon films were deposited on silicon substrates by the pulsed laser deposition method under a magnetic field. A composition-graded intermediate layer with a composition gradient from the substrate to the film was used to enhance the adhesion. It was found that adhesion was dependent on the thickness and composition gradient of the intermediate layer. For diamond-like carbon films deposited at room temperature, intrinsic stress in the interlayer played a key role. When an intermediate layer with a thickness of about 103 nm was used, the intrinsic stress was maximum and adhesion was poor. For films deposited at 60 °C and 100 °C, thermal stress and intrinsic stress should be considered together. Very thin intermediate layers ( 34 nm) were not suitable for good adhesion due to the presence of thermal stress. Adhesion was poor when the thickness of the intermediate layer was about 178 nm owing to imposition of the intrinsic stress. A composition profile with an exponent greater than 1 (silicon-riched) was beneficial to good adhesion.