Compressive-stress-induced formation of thin-film tetrahedral amorphous carbon

TLDR

Tetrahedral amorphous carbon (ta‑C) is a newly identified allotrope of carbon that was previously considered unlikely to exist. The study proposes a model explaining ta‑C film formation and structure based on compressive stress from shallow carbon ion implantation. The model attributes film growth to compressive stress generated by carbon ions implanted at shallow depths during filtered vacuum arc deposition. Experimental growth of thin ta‑C films using a filtered vacuum arc, with beam energies between 15 and 70 eV, produced high film stress, a graphitic surface, and simulations confirmed that these impact energies generate the required compressive stress.

Abstract

Thin tetrahedrally coordinated amorphous carbon (ta-C) films have been grown using a filtered vacuum arc. ta-C is a new allotrope of carbon whose existence was previously thought to be unlikely. A model is proposed which accounts for the formation and structure of these films on the basis of the compressive stress generated by the shallow implantation of carbon ions. An optimal range of beam energies between 15 and 70 eV, a high film stress, and a graphitic surface are predicted and confirmed by experimental evidence. Computer simulation of the growth confirms that high compressive stress is generated by impact energies in this range.