Investigation of mechanism of smear formation from diamond-like carbon films on heating
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TECHNICAL PAPER
Investigation of mechanism of smear formation from diamond-like carbon films on heating Hiroshi Tani1
•
Renguo Lu1 • Shinji Koganezawa1 • Norio Tagawa1
Received: 31 August 2020 / Accepted: 18 September 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The formation of head smears during the heat-assisted magnetic recording is a significant problem that must be addressed to ensure the reliability of the head-disk interface. In this study, the formation of a head smear by diamond-like carbon (DLC) films on magnetic disks was analyzed through simulated heating experiments. DLC films with a thickness of 100 nm were prepared and heated on a hot plate in an environmental gas chamber. A smear was observed on a silicon wafer placed 3 mm above the DLC surface film after the heating of the film. The smear amount was quantified based on the intensity of the carbon peak of the smear, which was measured by X-ray photoelectron spectroscopy. In air, the carbon concentration decreased with the heating temperature, while in nitrogen, it increased. Further, the carbon concentration of the smear formed in air was lower than that in nitrogen. A comparison of the smears formed by DLC films with different hydrogen concentrations showed that a greater amount of the decomposition gases was generated from the DLC films with a higher hydrogen concentration and that this value increased at lower temperatures. This result suggests that DLC films with low hydrogen concentrations generate smaller amounts of the decomposition gases during heating than those with high hydrogen concentrations. In addition, the results of Raman spectroscopy suggested that the DLC films get degraded during heating, resulting in the generation of hydrocarbon gases because the films contain carbon and hydrogen. Moreover, since peaks related to fragments with atomic masses of 250–500 atomic mass units were observed in the time-of-flight secondary ion mass spectrometry spectra of the smears, it can be concluded that the smears consist of hydrocarbons with relatively higher molecular weights.
1 Introduction Efforts are underway to increase the areal density of hard disk drives (HDDs), given the surge in the demand for the archiving of digital data. To realize these increases in the areal density, heat-assisted magnetic recording (HAMR) is a suitable method for use with various magnetic recording technologies (Challener et al. 2009). In the case of HAMR, with respect to the head-disk interface (HDI), the disk surface is heated to 200–400 °C while the head surface is heated to 100–200 °C. Kiely et al. concluded that the head smear formed during this heating process can significantly affect not only the stability of the HDI but also the transmission efficiency of thermal energy from the near-field transducer of the magnetic head to the recording medium in
& Hiroshi Tani [email protected] 1
HAMR systems (Kiely et al. 2017). Thus, the formation of head smears during HAMR is a si
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