Spectroscopy of homogeneous deuterated hydrocarbon films redeposited from a T-10 tokamak plasma discharge

Homogeneous deuterated hydrocarbon films redeposited from a deuterium plasma discharge inside the T-10 tokamak vacuum chamber are studied using photoluminescence methods; EXAFS, EPR, and IR spectroscopies; and temperature measurements. The photoluminescence excitation spectra of sp ³-sp ² nanostructures of tokamak films are compared with those of sp ² nanostructures of C60 fullerite films. The effect of defect states on photoluminescence and its temperature quenching is discussed. It is concluded that the model of temperature luminescence quenching for homogeneous deuterated tokamak films is similar to that for amorphous a-C:H films.     

Adsorption states of protium and deuterium in redeposited polymer hydrocarbon films from a T-10 tokamak

Free redeposited hydrocarbon films (flakes) with a high content of deuterium and hydrogen formed in the T-10 tokamak operating at the Russian Research Centre (RRC) “Kurchatov Institute” are studied using thermal desorption spectroscopy (TDS), infrared (IR) spectroscopy, and X-ray diffraction (XRD) analysis. According to the XRD data, the films contain scattering elements with dimensions of about 1 nm and weakly ordered structures. The TDS curves for D₂ (H₂) consisting of two groups of peaks at 450–800 and 900–1000 K turn out to be sufficiently similar to the spectra of nanographite obtained by milling graphite mechanically. Two main adsorption states with activation energies of ≈0.65 and ≈1.25 eV/N corresponding to hopping diffusion and resonance mechanisms, respectively, were discovered. The difference between the IR spectra of reddish-gold and dark-brown films is due to both a weaker degree of C-H hybridization of dark films and their disordered carbon network whose ends are connected to CD_2,3 fragments.     

Electron structure investigations of homogeneous hydrocarbon films formed in plasma conditions of T-10 tokamak

Electron structure investigations of smooth hydrocarbon thick films with a high atomic D/C ratio, redeposited from deuterium plasma discharge onto the vacuum vessel regions of the T-10 tokamak, are continued. For the first time, the investigations of both film sides and in a valence band region were performed by X-ray photoemission spectroscopy, combined with “conventional” measurements of survey spectra, C1s, O1s core levels, and by using Auger X-ray electron spectroscopy for sp ²/sp ³ ratio determination. The distinctions of electron structure of both sides of flakes which were noticed earlier using another techniques, were found, differing from the structure of thin films deposited in cleaning discharges of a low-temperature plasma. It is shown how these differences are connected with different processes of film deposition in tokamaks.     

EPR and photoluminescence spectra of smooth CD<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> films from T-10 tokamak: The effect of iron impurity

The electron and spin structure of thick smooth hydrocarbon CD _x films (“flakes”) with a high relative deuterium concentration of x ~ 0.5, redeposited from deuterium plasma discharge onto the walls of the vacuum chamber of the T-10 tokamak and containing ~1 at % of 3d-metal impurities due to erosion of the chamber walls, are studied using electron paramagnetic resonance (EPR) and photoluminescence (PL). The resulting spectra are compared for the first time to the EPR and photoluminescence spectra of polymer (soft) a-C:H(D) films (H(D)/C ~ 0.5), which are considered model analogues of smooth CD _x films. A certain similarity of the CD _x films with a-C:H films was found in the electronic structure of the valence band. At the same time, the differences in the EPR and photoluminescence spectra were observed due to the presence of 3d-metal impurities in the CD _x samples, contributing to the conversion of sp ³ → sp ² in the formation of films in the tokamak and upon heating and thermal desorption. An impurity of, presumably, 3d metals was detected for the first time by EPR in the a-C:H films in an amount of approximately 0.2 ppm, related to the evaporation of graphite.