Cluster-Type Structure of Amorphous Smooth Hydrocarbon CD x Films (x ~ 0.5) from T-10 Tokamak

• Published in: Surface investigation, x-ray, synchrotron and neutron techniques x-ray, synchrotron and neutron techniques, 2017-11, Vol.11 (6), p.1208-1215
• Main Authors: Svechnikov, N. Yu, Stankevich, V. G., Kolbasov, B. N., Zubavichus, Y. V., Veligzhanin, A. A., Somenkov, V. A., Sukhanov, L. P., Lebedev, A. M., Menshikov, K. A.
• Format: Article
• Language: English
• Subjects: Amorphous structure; Aromatic compounds; Atomic structure; Carbon; Chain branching; Chemical bonds; Clusters; Crosslinking; Deuterium; Electronic structure; Forming; Fractal models; Graphene; Hydrocarbons; Infrared spectra; Lattice vacancies; Neutron diffraction; Spectrum analysis; Structural members; Synchrotron radiation; Tokamak devices; X-ray scattering
• ISSN: 1027-4510; 1819-7094
• DOI: 10.1134/S1027451017060349

Structure of smooth hydrocarbon CDx films with a high deuterium ratio x ~ 0.5 redeposited from T-10 tokamak D-plasma discharges (NRC Kurchatov Institute, Moscow) has been studied. For the first time, small and wide angle X-ray scattering technique using synchrotron radiation and neutron diffraction have been employed. A fractal structure of CDx films is found to consist of mass-fractals with rough border, surface fractals (with rough surface), plane scatterers and linear chains forming a branched and highly cross-linked 3D carbon network. The found fractals, including sp2 clusters, are of typical size ~1.60 nm. They include a C13 fragment consisting of three interconnected aromatic rings forming a minimal fractal sp2 aggregate 9 × C13. These graphene-like sp2 clusters are interconnected and form a 3D lattice which can be alternatively interpreted as a highly defective graphene layer with a large concentration of vacancies. The unsaturated chemical bonds are filled with D, H atoms, linear sp2 C=C, C=O, and sp3 structural elements like C-C, C-H(D), C-D2,3, C-O, O-H, COOH, CxD(H)y found earlier from the infrared spectra of CDx films, which are binding linear elements of a carbon network. The amorphous structure of CDx films has been confirmed by the results of earlier fractal structure modeling, as well as by researches with X-ray photoelectron spectroscopy which allow finding a definite similarity with the electron structure of their model analogues — polymeric a-C:H and a-C:D films with a disordered carbon network consisting of atoms in sp3 + sp2 states.