Abstract
The tribological properties and scratch resistance of MoS2 bilayer deposited on SiO2/Si substrates prepared via chemical vapor deposition are investigated. Friction force microscopy (FFM) is employed to investigate the friction and wear properties of the MoS2 bilayer at the nanoscale by applying a normal load ranging from 200 to 1,000 nN. Scratch resistance is measured using the scratch mode in FFM based on a linearly increasing load from 100 to 1,000 nN. Kelvin probe force microscopy (KPFM) is performed to locally measure the surface potential in the tested surface to qualitatively measure the wear/removal of MoS2 layers and identify critical loads associated with the individual failures of the top and bottom layers. The analysis of the contact potential difference values as well as that of KPFM, friction, and height images show that the wear/removal of the top and bottom layers in the MoS2 bilayer system occurred consecutively. The FFM and KPFM results show that the top MoS2 layer begins to degrade at the end of the low friction stage, followed by the bottom layer, thereby resulting in a transitional friction stage owing to the direct contact between the diamond tip and SiO2 substrate. In the stable third stage, the transfer of lubricious MoS2 debris to the tip apex results in contact between the MoS2-transferred tip and SiO2. Nanoscratch test results show two ranges of critical loads, which correspond to the sequential removal of the top and bottom layers.
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This study was supported by the Research Program funded by the SeoulTech (Seoul National University of Science and Technology, Republic of Korea).
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Hyo-sok AHN. He awarded his B.S. and M.S. degrees in mechanical engineering from Seoul National University, Republic of Korea, in 1980 and 1982, respectively. Then he obtained his Ph.D. degree in tribology from University of Wales (UK) in 1988. He had worked as a research scientist at the Korea Institute of Science and Technology (KIST) for 20 years before he moved to Seoul National University of Science and Technology in 2005. He had served as the editor, the director of general affairs, and head auditor of the Korea Society of Tribology (KST). He spent a year (1994) in ceramics division at the National Institute for Standards and Technology (USA) as a guest researcher. He was appointed as the director of Low Friction and Wear Laboratory in 1998, one of the national research laboratories honored by the Korean government. He is the recipient of several awards in recognition of his outstanding achievement and services in research and education. He had contributed to international tribology community as the keynote speaker, committee member, and advisory board member of several international conferences including the STLE/ASME International Joint Tribology Conference (2007). His research lies in the fields of scanning probe microscopy, nano-/micro-tribology, thin films, and plasma-sprayed ceramic coatings. His current major interest is directed to the evaluation of tribological and mechanical properties of nanoscale thin films using scratch test at various scales.
Si-hwan KIM. He is an integrated Ph.D. student at the department of transdisciplinary studies, Seoul National University, Seoul, Republic of Korea. He obtained his B.Sc. (dual degree) in manufacturing systems and design engineering programme from University of Northumbria at Newcastle (UK) and Seoul National University of Science and Technology (Republic of Korea) in 2018 and subsequently has been working as a research scientist at the Biomedical Research Institute, Seoul National University Hospital. His current research interests include the medical image processing with machine learning & deep learning, medical physics for CT & MRI, and nano-biological imaging.
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Kim, Sh., Ahn, Hs. Nanotribological properties and scratch resistance of MoS2 bilayer on a SiO2/Si substrate. Friction 11, 154–164 (2023). https://doi.org/10.1007/s40544-022-0595-8
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DOI: https://doi.org/10.1007/s40544-022-0595-8