Dwivedi, N., Sunkara, S. V., Dhand, C., Yeo, R. J., Srivastava, A. K., Sankaranarayanan, S. K. R. S., Dragoe, D., Esaulov, V. A., & Bhatia, C. S. (2025). Large manipulation of competing bonding phases in ultrathin carbon layer system. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 714, 136548. https://doi.org/10.1016/j.colsurfa.2025.136548
Abstract:
The extent of sp3 bonding governs the functional properties of amorphous carbon films, by changing their density, Young’s modulus and hardness, which in turn affects their corrosion resistance, tribological properties and more. However, the sp3 bonding and other structural properties of such films at the ultrathin level, especially for sub-10 nm films, remain elusive. Here, we experimentally probe and quantify the bonding network of ∼0.7–10 nm amorphous carbon films. With decreasing carbon thickness, the films undergo giant structural modification with a decrease in sp3 bonding. Molecular dynamics simulations provide further insights into the observed variations in sp2 vs. sp3 bonding characteristics. We discover that the structural transformation is also substrate-dependent, with the films on metallic substrates yielding lower sp3 bonding than on silicon. Moreover, engineering the film-metal substrate interface via atomically thin silicon nitride promotes the sp3 bonding of < 3 nm-thick carbon films. We also observe that the sp3 bonded carbon network is destroyed when ion bombardment or sputter-etching is performed. This work provides crucial fundamental insights into the structure-characteristics modifications that may arise when engineering sub-10 nm amorphous carbon based films.
License type:
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Funding Info:
This research was partially supported by the Department of Science and Technology (DST), India through DST/TDT/AM/2022/253 project. S.K.R.S. acknowledges the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, which was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.