Internal stress reduction in diamond like carbon thin films by ion irradiation

Abstract

The stress-state of diamond like carbon (DLC) film was monitored in situ during Xe, Ar, Ne, and C irradiation. All irradiations were observed to produce a reduction in the as-deposited compressive stress. We have modeled the irradiation induced stress reduction in DLC by considering the different bond states of carbon that are possible in these materials, i.e. sp 2 and sp 3. An Avrami–Johnson–Mehl analysis of irradiation induced transformation indicates that at low doses the transformation occurs in one-dimensional-like volumes associated with non-overlapping collision cascades. As the irradiation dose increases, a full transformation occurs at the peak in the irradiation damage profile. With further increasing dose, the transformation product spreads out from the peak damage region. The rate of stress change is well correlated with the displacement damage produced in the collision cascade at a low dose linear region of σ – φ curves.