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

Abstract

Structure of smooth hydrocarbon CD x 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 CD x 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, C x D(H) y found earlier from the infrared spectra of CD x films, which are binding linear elements of a carbon network. The amorphous structure of CD x 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.