Growth of diamond by DC Arcjet Plasma CVD: From nano-sized poly-crystal films tomillimeter-sized single crystal grain

摘要

A 30 kW-powered DC Arcjet Plasma enhanced chemical-vapor deposition (CVD) system was applied to growdiamonds which included the nano-crystal free-standing film, the nano-/micro-crystal layered free-standingfilm, the gradient micro-crystal free-standing film and the millimeter-sized grain. The free-standing filmquality, such as the roughness, the sp~2 content, the residual stress and the grain morphology, was studied by anatomic force microscope (AFM), Raman spectra, a scanning electron microscope (SEM) and a high resolutionelectron microscope (HREM). In large-sized grain deposition, as-grown deposit was obtained about1 x 1 x 1 mm~3 in size under the condition of 10 μm/h of the substrate moving speed without Nitrogenenhancement. Characterized by Raman spectra and Laue back reflection X-ray diffraction, the deposit wasproven to be single crystal diamond with small grains coving its surfaces. The growth rate was about 30 um/h.Optical emission spectrum (OES) was utilized to characterize gas phases in the plasma for diamond deposition.The mean electron temperature (Te) in the plasma was calculated based on the value of the emission intensityratio ofI_H/I_HTe varied from 0.33 eV to 0.5 eV depending on the concentration of CH_4 in H_2 from 1.0% to 25%.C2 radical was found to be the dominant carbon source compared with CH radical. The influence of the radicalon the morphology of diamond was discussed. It was found that the nano-crystal could be grown when theratio of the emission intensity, WIG', was larger than 8.