Large Stress Reduction Induced by sp² Clustering in Tetrahedral Amorphous Carbon Films

The intrinsic stress of tetrahedral amorphous carbon film as a function of annealing temperature is investigated. The film was deposited using the filtered cathodic vacuum arc technique and subsequently annealed at various temperatures. The stress is determined by Stoney’s equation using surface profilometry, and the microstructure is studied using atomic force microscopy, visible and ultraviolet Raman spectroscopy. It is found that as the annealing temperature increases the film stress decreases slowly up to 500 oC and then falls quickly at 600 oC. It is interesting to note that at this temperature sp3 fraction retains while sp2 clustering begins, which contributes to the sharp decrease in the stress.