Regenerative Sooting Research Articles

Amorphous carbon films in direct current magnetron sputtering from regenerative sooting discharge

We present results of carbon coatings on metal substrates in cylindrical hollow cathode (CHC) direct current magnetron sputtering. This is a new technique for making amorphous carbon films by CHC magnetron sputtering from a regenerative sooting discharge. The carbon films are deposited on Cu and Al substrates in a Ne atmosphere and compared with the films of carbon soot on the same materials produced from a conventional 80A arc discharge between graphite electrodes in a He background gas. Raman spectroscopy reveals the existence of graphite and diamond-like structures from the arc discharge while in CHC magnetron sputtering, graphite-like structures are dominant. X-ray diffraction data of samples from the arc discharge show nano-size precipitates of Al 4C 3 of rhombohedral and hexagonal form for the aluminium sample and probable formation of diamond and hexagonal carbon in copper whilst in magnetron sputtering we obtain amorphous carbon films. Scanning electron microscope images of the surface show a collection of loose agglomerates of carbon particles in the arc discharge whereas, for magnetron sputtering, structures are regular with smooth edges and fine grains.

Ion implantation into aluminum and copper by a beam of carbon nanoparticles from regenerative sooting discharges

We present a new technique to generate light carbon nanoparticles from regenerative sooting discharges and its use for ion implantation on aluminum and copper surfaces at an energy of 40 keV. Films formed at fluences up to 3 × 10 15 C +/cm 2 for aluminum and 10 16 C +/cm 2 for copper are studied using Raman spectroscopy, X-ray diffraction and atomic force microscopy. Raman spectroscopy reveals the existence of graphite and diamond like structures in all samples. Precipitates of Al 4C 3 of rhombohedral and hexagonal types were found in the nanometer ranges from the X-ray diffraction pattern for aluminum samples and the probable formation of body-centered cubic diamond and hexagonal carbon in copper samples. The average grain sizes of Al 4C 3 were calculated ∼40 nm for Al and ∼35 nm for Cu. Mass spectra from a graphite hollow cathode duoplasmatron ion source are also presented. Atomic force microscopy images of a Cu sample also support the existence of 46 nm structures. Light carbon nanoparticles are readily available from the ion source in which a special carbonaceous environment creates regenerative soot. Support gas Ar produces more C 3 than Ne.

C3 as the dominant carbon cluster in high pressure discharges in graphite hollow cathodes

Results are presented that have been obtained while operating the graphite hollow cathode duoplasmatron ion source in dual mode under constant discharge current. This dual mode operation enabled us to obtain the mass and emission spectra simultaneously. In mass spectra C3 is the main feature but C4 and C5 are also prominent, whereas in emission spectra C2 is also there and its presence shows that it is in an excited state rather than in an ionic state. These facts provide evidence that C3 is produced due to the regeneration of a soot forming sequence and leave it in ionic state. C3 is a stable molecule and the only dominant species among the carbon clusters that survives in a regenerative sooting environment at high-pressure discharges.

A study of population inversion of He I and Ne I in regenerative sooting discharges

The mechanisms for population inversion among the excited states of He I and Ne I in regenerative sooting discharges have been investigated as a function of the geometry and the physical parameters of the graphite hollow cathode sources. The effect of the state of sooting of the hollow cathode, the gas pressure and the role of the cycling of idis on the population inversion of the excited He I and Ne I levels have been investigated.

The excited states of the neutral and ionized carbon in the regenerative sooting discharges

We report the mechanisms of production and the state of excitation of the neutral and singly charged monatomic carbon in the regenerative soot as a function of the discharge parameters in graphite hollow cathode (HC) sources. Two distinctly different source configurations have been investigated. Comparisons of the level densities of various charged states of C1 have identified the regenerative properties of the C radicals in graphite HC soot.

Regenerative soot as a source of broad band VUV light

A mechanism is proposed for the emission of a broad band VUV light to be emitted from the regenerative sooting discharges on the basis of unusually intense intercombination lines of C+(CII) and C++(CIII) that have been observed. Comparison of these high intensity intercombination lines with the allowed transitions of the highly excited and ionized C constituents of the sooting discharge indicates that one can exploit this mechanism to employ the regenerative soot as a VUV source. The emission of such a broad VUV band from the sooting discharges depends critically on the high energy electrons, metastable gas atoms and C ions trapped by the 3D cusp magnetic field contours.

Role of the kinetic and potential sputtering in the regeneration of the soot

We have used the photoemission spectroscopy of the graphite hollow cathode sooting discharge to identify the roles played by the kinetic and potential sputtering, respectively. Our indicators are the relative densities of the sputtered carbon C, the Ne metastable atoms, and the ionized components (Ne+) of the regenerative sooting plasma. We find that the metastable atoms are the main agents for the regeneration of the soot.

Sputtering and formation of C 1 and C 2 in the regenerative sooting discharge

Photoemission spectroscopy of the regenerative soot in neon's glow discharge plasma reveals the contributions from the sputtered atomic and molecular carbon species. We present the pattern of sputtering and the formation of monoatomic C 1 and diatomic C 2 as a function of the discharge current, the support gas pressure and the number densities of the excited and ionized neon as the active constituents of the carbonaceous plasma.

Carbon cluster formation in regenerative sooting plasmas

Laboratory formation of large carbon clusters C m ( m≤10 4) in carbonaceous plasmas is studied by using a specially designed ion source. Carbon is introduced into the glow discharge plasma by graphite sputtering. Regenerative sooting plasma creates clustering environment. Velocity spectra of the extracted clusters indicates the mechanisms operating in the soot.