Ab Initio Investigation on Cu/Cr Codoped Amorphous Carbon Nanocomposite Films with Giant Residual Stress Reduction

Abstract

Amorphous carbon films (a-C) codoped by two metal elements exhibit the desirable combination of tribological and mechanical properties for widely potential applications, but are also prone to catastrophic failure due to the inevitable residual compressive stress. Thus far, the residual stress reduction mechanism remains unclear due to the insufficient understanding of the structure from the atomic and electronic scale. In this paper, using ab initio calculations, we first designed a novel Cu/Cr codoped a-C film and demonstrated that compared with pure and Cu/Cr monodoped cases, the residual stress in Cu/Cr codoped a-C films could be reduced by 93.6% remarkably. Atomic bond structure analysis revealed that the addition of Cu and Cr impurities in amorphous carbon structure resulted in the critical and significant relaxation of distorted C-C bond lengths. On the other hand, electronic structure calculation indicated a weak bonding interaction between the Cr and C atoms, while the antibonding interaction was observed for the Cu-C bonds, which would play a pivot site for the release of strain energy. Those interactions combined with the structural evolution could account for the drastic residual stress reduction caused by Cu/Cr codoping. Our results provide the theoretical guidance and desirable strategy to design and fabricate a new nanocomposite a-C films with combined properties for renewed applications.

First principles investigation on energetics, structure, and mechanical properties of amorphous carbon films doped with B, N, and Cl

“…This phenomenon can be explained by the higher fraction of distorted bond angle for N-doped than B-doped a-C films, which is higher impact on reduction of bulk modulus because the distorted bond angle is relaxed larger than bond length by lattice vibrations during stress calculation using VASP. Similar results have been reported by other researchers 4,16 .…”

“…Amorphous carbon (a-C) films have received significant attention due to their reliable structures and superior mechanical, chemical and electronic properties 1–3 , making them a strong candidate as a hard mask material for the fabrication of future integrated semiconductor devices. For wider applications, however, it is still necessary to overcome the current limitations such as high internal stresses, low blocking nature of fluorine attack to sub-layers, and low temperature stability 4 . In order to eliminate the drawbacks and enhance properties of the a-C films, tremendous approaches have been carried out.…”

“…The reason why we have chosen those three main dopant elements is because a-C films doped with B, N, and Cl elements are mainly used in semiconductor devices rather than other dopants such as Si, Cu, Cr, Ti, W, Ga, and Al, which significantly reduce transparency of incident light 4 . In addition, even though the several experimental studies on those three dopants have been reported, no guidelines exist for improving the a-C films because the relationship between the structure of a-C films and its characteristics remain unclear, which is a limiting factor for its effective use in any device application 11 .…”

Mechanism of contact pressure-induced friction at the amorphous carbon/alpha olefin interface

“…In recent years, amorphous carbon (a-C) films have become increasingly popular in both the scientific and engineering communities because of their impressive combination of high hardness, low friction coefficient, and chemical inertness. [1][2][3][4] These properties can provide effective protection against serious mechanical or chemical damage of moving mechanical components, such as tools, 5 automobile engines, 6 aerospace components, 7 and artificial joints. 8,9 However, a-C films inevitably undergo self-consumption, which severely limits their lifetime and reliability and ultimately leads to the catastrophic failure of the coated surface.…”

The influence of hydrogen concentration in amorphous carbon films on mechanical properties and fluorine penetration: a density functional theory and ab initio molecular dynamics study

“…However, for wider applications, it is still necessary to overcome the current limitations such as high internal stresses, low blocking nature of uorine attack to sub-layers, and low temperature stability. 4 In order to eliminate the aforementioned drawbacks and enhance the properties of the a-C lms, the inuence of hydrogen to modify their structure during the deposition process was studied.…”