Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H-2 into the deposition gas chemistry. Electronically excited species of CN, C-2, Ar, N-2, CH, H-beta, and H-alpha were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T-2g phonon at 1333 cm(-1) peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit "coral" and "cauliflower-like" morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 mu m. (C) 2015 AIP Publishing LLC.