A Linear Microwave Plasma Source And Its Use In CVD Diamond

In this paper, different kinds of linear plasma sources have been summarized and compared. Basing on the review, a novel linearly coaxially coupled microwave plasma source have been designed and used to prepare diamond films.First, according to the geometrical characteristics of the long rod substrate, a new linear coaxial coupled microwave plasma source was designed. In this paper, a traditional widely used quartz tube linearly coaxially coupled microwave plasma device as the basis, through structural redesigned of the cavity and the microwave antenna to move the quartz tube. During the research,a lot of improvements had been made. Now, it can stable produce a 20 cm uniform linear microwave plasma at high pressure. To design the plasma source matched the size and shape features of substrate was the best way for the uniformly deposition diamond films.Deposition the diamond films on the surface of elongate beryllium oxide using linear plasma produced by self-developed linearly coaxially coupled microwave plasma device was investigated. It was found that without preliminary pretreatment beryllium oxide surface had uneven surface defects, results in uneven nucleation. So did not deposit a continuous diamond film on beryllium oxide surface after deposition process. The surface of beryllium oxide was smooth after polished with diamond powder. Smooth surface leaded to lower nucleation density, so failed to form a continuous diamond film after growth process. After grinded using sand paper and diamond powder the beryllium oxide surface defects increased and distributed uniformly. High and uniform nucleation was produced. Continuous diamond film was deposited after deposition process.The characteristic of diamond films deposited on beryllium oxide rod has been analyzed using SEM and Raman. According to the results of the characterization components and growth process of spherical diamond particles were analyzed. Cauliflower spherical diamond film was mainly composed of amorphous carbon and nano-diamond particles. It grown up mainly by means of disorder second nucleating based on the original nucleus as the center. At high methane concentration, the hydrocarbon radicals accumulated on the growth face to formed second nucleating. Second nucleating arising repeatedly suppressed the original nucleus to grow up. So formed spherical diamond particles composed by the small nano-diamond particles. Reduce the methane concentration could effectively inhibit second nucleating. Original nucleation particles grew up gradually and formed a complete grain.