Effect of pre-treatment of the substrate surface by energetic C⁺ ion bombardment on structure and nano-tribological characteristics of ultra-thin tetrahedral amorphous carbon (ta-C) protective coatings

Abstract

Depositing an ultra-thin tetrahedral amorphous carbon (ta-C) protective coating on the surface of the recording heads in magnetic tape drives can improve the tribological problems at the head/tape interface. In this work the effect of pre-treatment of the surface of AlTiC substrate (main bearing surface of head in contact with tape) by C+ ions of moderate energy (smaller than 400 eV) on the structural and tribo-mechanical behaviours of the coated surfaces is studied. Sample preparation consisted of two separate stages of surface pre-treatment and deposition of the protective film, and was done by means of filtered cathodic vacuum arc. Structure of the ta-C film and its interface with the substrate were studied by transmission electron microscopy and time-of-flight secondary ion mass spectrometry depth profiling. The results revealed the formation of a broader, dense atomically mixed layer at the ta-C film–substrate interface of the pre-treated samples comparing with that of the samples without pre-treatment. Chemical characterization of thin diamond-like carbon coatings was conducted by means of x-ray photoelectron spectroscopy and the surface pre-treatment was found to have a remarkable effect on increasing the sp3 hybridization fraction in the ta-C overcoat. Nano-tribological properties of the treated surfaces were examined using ball-on-flat wear test at very low load (20 mN). There was a good correlation between the surface and structure characteristics of the film, and the tribological results and the pre-treated surfaces presented a very low coefficient of friction and higher wear life. The experimental results demonstrate the effectiveness of bombardment of the surface with C+ ions of moderate ion energy to improve the structural and tribo-mechanical properties of the protective ta-C films on the magnetic head substrate material.

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

“…As sample 3SiN14CF possessed additional interfacial bonding due to the SiN x interlayer, the relatively higher interfacial adhesion observed in sample 3SiN14CF may be the reason for its slightly higher wear resistance than that of sample 17CF in the ball‐on‐disk tribological tests. Increased adhesion of the overcoat on the substrate has been shown to enhance the wear resistance of carbon‐based overcoats . We also performed rigorous long‐term wear tests to gain more insight into the role of the increased interfacial adhesion on the wear durability (wear resistance) of the overcoats, which will be discussed later.…”

“…In contrast, the 20‐nm thick monolithic 20CF overcoat deposited by the FCVA bi‐level energy process (350 eV for pretreatment followed by 90 eV for ta‐C deposition) was still present at the read/write element region even after 12.5 million meters of tape testing. The relatively higher wear durability of the 20CF overcoat can be attributed to two factors: 1) the higher sp 3 content present in the ta‐C overcoat, which contributed to its superior mechanical properties, and the formation of an atomically mixed interface due to the 350 eV carbon ions, which enhanced the adhesion of the overcoat to the AlTiC substrate . However, due to the higher contact pressure experienced at the skiving edge, the overcoat wore out at a greater rate in this area.…”

Biaxial strain effect of spin dependent tunneling in MgO magnetic tunnel junctions

“…The atomic fraction of each component (C-C sp 1 , C-C sp 2 , C-C sp 3 , C=O, and C-O) is obtained by integrating the associated Gaussian curves deconvoluted from the C 1s spectra after Shirley background subtraction. 16 Figure 1(d) shows a plot of the TMR versus the junction area before and after the deposition of DLC film at room temperature. The TMR ratio is defined by (R AP -R P )/R P , where R P and R AP are the junction resistance in the parallel (P) and anti-parallel (AP) alignment of the ferromagnetic electrodes, respectively.…”

“…DLC films are grown by filtered cathodic vacuum arc and a method used by Ehsan et al has been adopted that provides good adhesion along with high sp 3 content for enough strain. 16 Ion energy of about 100 eV is selected as it provides the highest fraction of sp 3 bonds with the maximum density and hardness.…”

Slippery and Wear-Resistant Surfaces Enabled by Interface Engineered Graphene

“…Moreover, the AlTiC-based read/write heads embedded with magnetic elements are used in hard disk drives (HDDs) and tape drives (TDs), which have strict low thickness budget for tribological overcoats. [4][5][6][7][8]29 For instance, for TDs to achieve areal densities (AD) ∼ 100 Gbits/in 2 by 2025 requires reduction of head overcoat thickness to <10 nm. This is extremely challenging as most previously used thicker (∼7− 100 nm) head overcoats had suffered either substantial removal or complete removal just after 1−2 million meters (Mm) of tape-head-wear (THW) tests.…”