Unusual stress behavior in W-incorporated hydrogenated amorphous carbon films

Unusual stress behavior was observed in W-incorporated hydrogenated amorphous carbon films prepared by a hybrid process composed of ion-beam deposition and magnetron sputtering. As the tungsten concentration increased from 0 to 2.8at.%, the residual compressive stress decreased by 50%, without significant deterioration in the mechanical properties. This was followed by a rapid increase and a gradual decrease in the residual stress with increasing W concentration. High-resolution transmission electron microscopy analysis and first-principle calculations show that the reduced directionality of the W–C bonds in the W-incorporated amorphous carbon matrix relaxes the stress caused by the distorted bonds.