title: Surface Energy in Nanocrystalline Carbon Thin Films: Effect of Size Dependence and Atmospheric Exposure.
abstract: Surface energy (SE) is the most sensitive and fundamental parameter for governing the interfacial interactions in nanoscale carbon materials. However, on account of the complexities involved of hybridization states and surface bonds, achieved SE values are often less in comparison with their theoretical counterparts and strongly influenced by stability aspects. Here, an advanced facing-target pulsed dc unbalanced magnetron-sputtering process is presented for the synthesis of undoped and H/N-doped nanocrystalline carbon thin films. The time-dependent surface properties of the undoped and H/N-doped nanocrystalline carbon thin films are systematically studied. The advanced plasma process induced the dominant deposition of high-energy neutral carbon species, consequently controlling the intercolumnar spacing of nanodomain morphology and surface anisotropy of electron density. As a result, significantly higher SE values (maximum = 79.24 mJ/m2) are achieved, with a possible window of 79.24-66.5 mJ/m2by controlling the experimental conditions. The intrinsic (size effects and functionality) and extrinsic factors (atmospheric exposure) are resolved and explained on the basis of size-dependent cohesive energy model and long-range van der Waals interactions between hydrocarbon molecules and the carbon surface. The findings anticipate the enhanced functionality of nanocrystalline carbon thin films in terms of selectivity, sensitivity, and stability.
authors.affiliation: Center for Advanced Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma-Nano Materials (IPNM), Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Manish
authors.identifier: 0000-0002-0141-5318
authors.initials: M
authors.lastname: Kumar
authors.affiliation: Center for Advanced Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma-Nano Materials (IPNM), Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 440-746, Republic of Korea.|Department of Textile Processing, National Textile University , Faisalabad 37610, Pakistan.
authors.forename: Amjed
authors.initials: A
authors.lastname: Javid
authors.affiliation: Center for Advanced Plasma Surface Technology (CAPST), NU-SKKU Joint Institute for Plasma-Nano Materials (IPNM), Advanced Materials Science and Engineering, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
authors.forename: Jeon Geon
authors.initials: JG
authors.lastname: Han