Stress-dependent adhesion and sliding-induced nanoscale wear of diamond-like carbon studied using in situ TEM nanoindentation

• Published in: Carbon (New York) 2022-06, Vol.193, p.230-241
• Main Authors: Liang, Jhih H., Milne, Zac, Rouhani, Mehdi, Lin, Yi-Pan, Bernal, Rodrigo A., Sato, Takaaki, Carpick, Robert W., Jeng, Yeau R.
• Format: Article
• Language: English
• Subjects: Adhesion; Atomic force microscopy; Carbon; Contact stresses; Covalent bonds; Damage; Diamond-like carbon; Diamonds; DLC; Mechanical properties; Nanoindentation; Nanotribology; Shear stress; Sliding; Surface energy; TEM; Transmission electron microscopy; Tribology; Wear mechanisms; Wear resistance
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2022.03.030

We present the first in situ transmission electron microscope (TEM) study of extended sliding of diamond-like carbon (DLC) on diamond. We show how the tribological properties of amorphous carbon (a-C) reach their limit by exploring the onset of wear for the harsh condition of sliding against diamond in vacuum. A particularly hard, hydrogen-free member of the DLC family, a-C is of wide technological interest, but the mechanisms by which damage occurs during tribological contact are not well understood. Real-time TEM imaging of the nanoscale contact area provides insight into wear mechanisms and damage. We show that at high normal stresses with full sliding contributing to additional shear stress, the initially low adhesion of the a-C-diamond interface rapidly increases at a rate greater than is seen in similar silicon-diamond contact studies. We propose that high contact stresses wear away a relatively low surface energy sp2-rich layer on the outer a-C surface, exposing sp3-rich sub-layers which can form covalent bonds that require more tensile force to be broken, leading to higher adhesion and an acceleration of wear. [Display omitted] •The first in situ TEM study of extended sliding of DLC on diamond.•Revealed real-time TEM imaging of sliding-induced wear.•Disclosed dependency of adhesion on stress and speed.•The initially low adhesion of the a-C-diamond interface rapidly increases.•High contact stresses wear away sp2-rich layer on the a-C surface.