Nanocrystalline/amorphous biphase enhanced mechanical properties in multilayer carbon films

Abstract

This study reports the nanostructure evolution and mechanical properties improvement in the nanocrystalline/amorphous multilayer carbon films. Electron cyclotron resonance sputtering and electron/ion alternative irradiation techniques were used to deposit the multilayer carbon films with the total film thicknesses ranging from 130 to 10nm and the single layer thicknesses ranging from 4 to 1nm. The high resolution transmission electron microscopy observation showed that the interface between nanocrystalline layer and amorphous layer evolved from an original toothed structure to a mixed biphase structure, and the nanocrystallite size in nanocrystalline layer decreased when layer thickness was reduced from 4 to 1nm. The nano-indenter tests showed a significant improvement in hardness of multilayer film when single layer thickness was reduced from 4 to 1nm. The scratch tests revealed that good scratch resistance could be preserved in the multilayer film with 1nm single layer thickness when total film thickness was only 10nm. This work may shed light on the ultrathin multilayered coating technology.