Development of an Ionized Physical Vapor Deposition System for Superhard Amorphous Carbon Coating

Abstract

The purpose of this work is to development and demonstrate that the ionized physical vapor deposition system, which consists of four plasma sources (FCVA, L-ALIS, ALIS and magnetron sputtering) enables to produce of superhard amorphous carbon thin films. The superhard amorphous carbon films was designed based on the multilayer film comprising alternating layers of ta-C layers and a-C:H layers, which the a-C:H layer has been fabricated by L-ALIS source and the ta-C layer have been fabricated by FCVA source. The morphologies, microstructure and mechanical properties of the single layer ta-C, single layer a-C:H and multilayer ta-C films deposited on Si and SUS304 substrate were systematically investigated. Results showed that the plasma biasing and substrate bias technique increases the energy of C+ ions. This phenomenon overcomes the nucleation barrier and subplantation occurs. The energetically enhanced deposition condition during FCVA facilitates the densification of the single layer ta-C films up to 3.32 g/cm3, leading to an increase in film hardness to 47 GPa. While the single layer a-C:H deposited under intense and highly energetic bombardment of molecular ions has a low sp3 content leading to density of 2.2 g/cm3

The multilayer structure effectively reduced the residual stress and restrained spalling of ta-C film, which frequently occurred in single layer structure. The hardness and elastic modulus of multilayer films increased with increase sp3 content of ta-C layer. Compared to the SUS304 substrate, multilayer films exhibited much high hardness and very low surface roughness. For the multilayer film alternating of ta-C layer deposited at substrate bias potential −80 V and a-C:H layer (M-3 film) had a high hardness of 37.6 GPa and good adhesion with the substrate. In addition, the high hardness, the multilayer films with good elastic strain to failure and high resistance to plastic deformation and cracking.

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