Abstract
Structure and properties of Cu-doped diamond-like carbon films (DLC) were investigated using ab initio calculations. The effect of Cu concentrations (1.56∼7.81 at.%) on atomic bond structure was mainly analyzed to clarify the residual stress reduction mechanism. Results showed that with introducing Cu into DLC films, the residual compressive stress decreased firstly and then increased for each case with the obvious deterioration of mechanical properties, which was in agreement with the experimental results. Structural analysis revealed that the weak Cu-C bond and the relaxation of both the distorted bond angles and bond lengths accounted for the significant reduction of residual compressive stress, while at the higher Cu concentration the increase of residual stress attributed to the existence of distorted Cu-C structures and the increased fraction of distorted C-C bond lengths.
Highlights
Diamond-like carbon (DLC) films are widely investigated due to their unique structures and excellent mechanical, electronic, optical, and magnetic properties,[1] which are used as a protective coating in various industrial applications, and considered in the fields of solar cell, magnetic disk storage devices, medical application and so on.[2,3,4] high level of residual compressive stress limits the films thickness to a few tens of nanometers and is the major drawback to their technological applications
Structural analysis revealed that the weak Cu-C bond and the relaxation of both the distorted bond angles and bond lengths accounted for the significant reduction of residual compressive stress, while at the higher Cu concentration the increase of residual stress attributed to the existence of distorted Cu-C structures and the increased fraction of distorted C-C bond lengths
We present an ab initio calculation based on density functional theory (DFT) to investigate the structure and properties of Cu-diamond-like carbon films (DLC) films with different Cu concentrations
Summary
Diamond-like carbon (DLC) films are widely investigated due to their unique structures and excellent mechanical, electronic, optical, and magnetic properties,[1] which are used as a protective coating in various industrial applications, and considered in the fields of solar cell, magnetic disk storage devices, medical application and so on.[2,3,4] high level of residual compressive stress limits the films thickness to a few tens of nanometers and is the major drawback to their technological applications. It has been shown experimentally that an effective way to avoid the high residual stress of DLC films is the introduction of a small amount of Cu during the growth process. It is well noted that the residual compressive stress is strongly dependent on the distorted atomic bonds in amorphous carbon structure. Due to the limited experimental characterization of the atomic bond structure, the effect of doped metal atoms on the atomic bond structure from the viewpoint of atomic scale is yet to be clarified, leading to the phenomenological explanation and controversy of stress reduction mechanism
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