Papers by Keyword: DC Arc Plasma Jet

Abstract: As an emerging brand new type of engineering material for a variety of important high technology applications, the deep understanding of the mechanical behavior of freestanding diamond films has become an emergent task of vital importance. Of the many deposition methods dc arc plasma jet has been regarded as the most promising technique for large area high quality and low cost production of freestanding diamond films. In the present paper, recent progress in mechanical properties of freestanding diamond films mainly by high power dc arc plasma jet with rotating arc root and gas recycling is reviewed. Testing methods for fracture strength and fracture toughness are discussed. Experimental data are presented and compared to that by MWCVD. Dc arcjet diamond films start to oxidize at about 700°C, however, oxidation up to 800°C for 10 min does not affect the fracture strength. Fracture mechanism is discussed. The strange mechanical behavior of freestanding diamond films is explained. It is surprising that CVD diamond film is such a kind of material which is strong, but full of different size of defects. It is hoped that the present paper will be helpful for those who wish to understand and use this brand new type of engineering material.

Abstract: . High quality diamond film wafers with different thickness are prepared by high power DC arc plasma jet CVD (DCPJ CVD) method using a CH4/Ar/H2 gas mixture. The effect of substrate temperature on the quality of diamond film was studied with theoretical analysis and experimental investigation. The results indicate that different structures in diamond film may grow with different substrate temperatures. The temperatures of 800°C, 900°C and 1000°C were tested in the experiments. The quality of diamond film showed the best at the temperature of 900°C. Characterization by X-ray diffraction, Raman spectroscopy and SEM analysis are also carried out.

Abstract: Micro-nanocrystalline diamond (M-NCD) Film may be successfully prepared on Mo substrate with DC arc plasmas jet deposition device. This paper studies the influences of carbon source concentration on the shape of M-NCD Film particles under circumstances of stable electric arc, and characterizes the grain size and quality of samples through SEM, AFM and Raman spectrum. The research result shows that, in the state of stable electric arc, relatively low carbon source concentration (1%) could deposit high-quality microcrystalline diamond film on the substrate, with a growth rate of up to 8.3μm/h and grain size of about 2～4μm; relatively high carbon source concentration (10% or 15%) could deposit high-quality nanocrystalline diamond(NCD) film on the microcrystalline diamond film at high speed, with a growth rate of up to above 12.6μm/h or 19.7μm/h, grain size of about 4～80nm and average grain size of 27.4nm.

Abstract: We investigated the residual stress in diamond films grown on molybdenum substrates as a function of different places in the same large sample. The diamond film wafers of Ф60 mm diameter were deposited at 900°C by high power DC arc plasma jet CVD method using a gas mixture of methane (1.8% vol.) and hydrogen ( 90% vol.). The grain sizes, obtained from the top view scanning electron microscopy (SEM) images, were found to become larger from center to the border in the same sample, and the x-ray diffraction indicated that the intensity of characteristic spectroscopy in same diamond film was changed from (220) to (111) with the increases of (311). Profile curves presented the appreciable difference of surface texture from center to edge. The film had 4.3GPa of residual compressive stress. Examination of the Raman spectra of the film revealed that residual stress in the film of up to approximately 0.70GPa, and the Raman spectroscopy shifts from 1332.99cm-1 at the center to 1331.17cm-1 at the border, which means the stress mode changed from compressive to tensile. These demonstrated a significant inhomogeneity of stress in diamond films. The differences have been attributed partly to high temperature inhomogeneity arc jet during growth and morphological aspects of the film growth. The relationships between stress and methane concentration, and substrate temperature are discussed in detail.