As the application of nanotechnology increases continuously, the need for controlled size nanoparticles also increases. Therefore, in this work, we discussed the growth mechanism of carbon nanoparticles generated in Ar+CH4 multi-hollow discharge plasmas. Using the plasmas, we succeeded in continuous generation of hydrogenated amorphous carbon nanoparticles with controlled size (25–220 nm) by the gas flow. Among the nanoparticle growth processes in plasmas, we confirmed the deposition of carbon-related radicals was the dominant process for the method. The size of nanoparticles was proportional to the gas residence time in holes of the discharge electrode. The radical deposition developed the nucleated nanoparticles during their transport in discharges, and the time of flight in discharges controlled the size of nanoparticles.
The chemical structure of diamond-like carbon (DLC) films was analyzed by Raman spectroscopy. The samples were DLC films synthesized by photoemission-assisted Townsend discharge (PATD). Group theory of the fundamental molecular structures suggested that the Raman spectrum consists of five bands with specific vibration modes, and the lineshape was represented by a modified Voigt-type formula. Analysis of the areas and positions of the bands resulted in the chemical structure of the DLC films with the sp2 cluster model. The model comprises conjugated and conductive clusters of sp2 carbons (sp2 clusters) floating in a non-conjugated and dielectric matrix of sp2 carbon, sp3 carbon, and hydrogen. The sp2 clusters were rather aliphatic for DLC films formed in low concentration of methane. The clusters grew to become aromatic with increasing methane concentration. The number of defects or dangling bonds increased similarly but were terminated with hydrogen for the films formed in a high methane concentration. The essential structure of DLC is the result of the development of random conjugation represented by the sp2 cluster model. We consider that DLC is a carbonaceous material in which conjugation increases slowly with time during the deposition process and which exhibits dielectric characteristics.
In this study, a chemometric approach for five-peak separation analysis of the Raman spectra of diamond-like carbon (DLC) films was investigated. DLC films were deposited by high-frequency inclusion high-power impulse magnetron sputtering and alternating current high voltage burst plasma chemical vapor deposition. We used the pseudo-Voigt function as an alternative to the conventional Voigt function and applied the nonlinear least squares method. The results not only facilitate automated analysis but also guarantee highly accurate results regardless of the analyst's level of expertise. This approach is expected to lead to consistent interpretation of Raman spectral analysis of DLC films and further research and understanding of the properties of DLC films.
The influence of a post‐annealing treatment on the chemical structure of a diamondlike carbon (DLC) film was clarified by Raman spectroscopy. The DLC films were synthesized by ionized deposition. The structures were elucidated via Raman analysis in conjunction with the sp 2 cluster model. The as‐prepared DLC film consisted of a dielectric matrix including sp 3 carbon, where sp 2 clusters were floating. When the post‐annealing treatment commenced, especially between 450 and 600°C, carbon─hydrogen bonds were cleaved, and the hydrogen atoms were desorbed from the film, creating defects or dangling bonds. The defects were reactive in growing sp 2 clusters that were strained with numerous defects because of the restricted degrees of freedom in the solid. As the post‐annealing temperature further increased, the clusters became dominant and the strain was gradually dissolved.
