Probing the Role of an Atomically Thin SiNx Interlayer on the Structure of Ultrathin Carbon Films

Abstract

Filtered cathodic vacuum arc (FCVA) processed carbon films are being considered as a promising protective media overcoat material for future hard disk drives (HDDs). However, at ultrathin film levels, FCVA-deposited carbon films show a dramatic change in their structure in terms of loss of sp3 bonding, density, wear resistance etc., compared to their bulk counterpart. We report for the first time how an atomically thin (0.4 nm) silicon nitride (SiNx) interlayer helps in maintaining/improving the sp3 carbon bonding, enhancing interfacial strength/bonding, improving oxidation/corrosion resistance, and strengthening the tribological properties of FCVA-deposited carbon films, even at ultrathin levels (1.2 nm). We propose the role of the SiNx interlayer in preventing the catalytic activity of Co and Pt in media, leading to enhanced sp3C bonding (relative enhancement ~40%). These findings are extremely important in view of the atomic level understanding of structural modification and the development of high density HDDs.

Understanding the Role of Nitrogen in Plasma-Assisted Surface Modification of Magnetic Recording Media with and without Ultrathin Carbon Overcoats

“…In the Raman spectra of the amorphous carbon films, the D peak arises due to the breathing mode of sp 2 carbon atoms in aromatic rings, whereas the G peak arises from the in-plane bond stretching motion of all pairs of sp 2 carbon atoms in both the aromatic rings and aliphatic chains of carbon. The G peak position is an important parameter to understand the microstructure of amorphous carbon films in terms of sp 3 and sp 2 carbon bonding, whereas the I D /I G ratio provides information about ring-like sp 2 cluster formation 12 30 31 32 . The value of the G peak position arising from the pulsed DC deposition of COCs in these samples was calculated to be 1586 ± 1 cm −1 whereas the I D /I G ratio was estimated to be 0.85 ± 0.01.…”

“…Figures 5a–5c show the deconvoluted C 1s core level spectra of samples S-4, S-5 and S-6, after background subtraction in Shirley mode. The deconvolution of the C 1s core level spectrum in each sample was performed with four Gaussian curves, which correspond to the sp 2 carbon bonding (sp 2 C), sp 3 carbon bonding (sp 3 C), C–O bonding and C = O bonding 12 14 18 20 33 34 ( see supplementary information S8.1 ). Since sp 3 C bonding is the key property of COCs in achieving excellent toughness, wear resistance and film coverage to effectively protect the underlying media 12 16 17 18 19 20 , hence, we mainly concentrate on estimating the sp 3 C bonding fractions by an area ratio method for all the ultrathin COCs.…”

“…However, sputtered COCs are unable to provide adequate protection for the media when they are thinned down to 2–3 nm or less 10 11 . Presently, plasma enhanced chemical vapor deposition (PECVD) is used to deposit 2.5–3 nm thin hydrogenated carbon (CH x ) overcoats 1 12 . However, when the thickness is reduced to below 2 nm, the protective characteristics of CH x -based COCs also start to deteriorate.…”

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

“…In general, ultrathin amorphous carbon films have gathered great technological interest as overcoats for magnetic storage devices, MEMS/NEMS, and AFM tips, owing to their excellent mechanical and tribological properties, and the capability for room‐temperature deposition . However, at the ultrathin film level, the role of the substrate and the film–substrate (FS) interface also become very important, and the wear and friction mechanisms at this level are not yet well understood.…”

Manufacturing and Characterization of a Carbon-Based Amorphous (a-CNX) Coating Material

“…In Raman spectra, from 1000 to 2000 cm -1 , microstructure of amorphous carbon film can be characterized by two prominent features such as the position of D (disorder) peak and G (graphitic) peak as well as by the intensity ratio of these two peaks, i.e., I D /I G . G peak centered around 1560 cm -1 is attributed to the inplane vibration of all sp 2 hybridized bonds, and D peak centered around 1350 cm -1 is attributed to having defect sites in sp 2 sites linking to the formation of sp 3 hybridization while I D /I G correlates to the sp 2 cluster fractions in organized carbon rings [54,55]. In Fig.…”