Interface Engineering and Controlling the Friction and Wear of Ultrathin Carbon Films: High sp³ Versus High sp² Carbons

Abstract

Understanding and engineering interfaces, and controlling the friction and wear of materials, are extremely important for many technological applications, particularly for magnetic storage technologies and micro-and nanoelectromechanical systems (MEMS and NEMS), where one sliding/moving surface comes into contact with another. Ultrathin carbon fi lms are generally employed in most of these technologies. However, their wear and friction mechanisms are not well understood, especially the role of the fi lm-substrate (FS) interface has not been deeply explored and discussed to date. This limits further developments in this fi eld. Through experimental and theoretical experiments, we are able to report on the engineering of a FS interface consisting of high sp 3and high sp 2 -bonded ultrathin carbon fi lms on Al 2 O 3 -TiC substrates by introducing a silicon nitride (SiN x ) interlayer and tuning the carbon ion energy. All carbon-based overcoats show a low coeffi cient of friction (COF) in the range of 0.08-0.16; however, the high sp 3 -bonded C/SiN x bilayer overcoat reveals the lowest and most stable friction. The friction mechanism is explained using an integrated framework of surface passivation, rehybridization, material transfer, tribolayer formation, and interfaces. We discover that FS interface engineering substantially reduces the wear of ultrathin carbon fi lms while maintaining/ reducing the friction. In general, this approach can be applied to control the friction and wear of ultrathin fi lms of diverse materials.

Ultrathin amorphous carbon films synthesized by filtered cathodic vacuum arc used as protective overcoats of heat-assisted magnetic recording heads

“…Deposition of sub-5-nm-thick a -C films under optimal FCVA working conditions, however, is challenging because the thickness of the highly sp 3 hybridized bulk layer, which controls the structure, thermal stability, nanomechanical/tribological properties, and oxidation resistance of the film, becomes comparable with the thicknesses of the sp 2 -rich intermixing and surface layers. This explains the increase of the sp 3 content with the carbon film thickness 23 and the use of seed underlayers to enhance sp 3 hybridization and improve the tribological properties of a -C films 24 , 25 . The principal objective of this study, therefore, was to examine the growth of ≤4-nm-thick a -C films under FCVA conditions conducive to the formation of a sufficiently thick bulk layer with high sp 3 content.…”

Unraveling the Friction Evolution Mechanism of Diamond‐Like Carbon Film during Nanoscale Running‐In Process toward Superlubricity

“…Achieving ultralow friction and wear of sliding interfaces [ 1–3 ] is always among the most challenging tasks in engineering design, largely due to a lack of predictive and fundamental approaches. Yet these issues are crucial for increasing energy efficiency and reducing energy consumption globally, as well as for ensuring reliable, sustainable, and safe operation of any technology with moving parts.…”

Boosting contact sliding and wear protection via atomic intermixing and tailoring of nanoscale interfaces

“…1A) (see Supplementary Discussions 1 and 2). Here, 4 eV is the energy of sputter-processed carbon, while 90 and 350 eV are the energies of carbon processed by a filtered cathodic vacuum arc (FCVA) ( 4 , 25 ). The thickness of the overcoat is a critical parameter to us because the development of many technologies is directly linked to the reduction of the overcoat thickness.…”

“…Conventionally, sp 3 bonding is the key parameter that governs wear resistance, while both sp 3 /sp 2 bonding and surface chemistry/surface passivation control the friction characteristics of amorphous carbon films ( 4 , 6 , 29 – 33 ). We uncover here many other novel critical parameters which govern the friction and wear behavior at the sub-10-nm thickness regime on all tribological scales.…”