Conical carbon nanofibers (CCNFs) have been synthesized on Si substrates coated with a Fe thin film of a few nanometers in thickness by a DC bias-enhanced microwave plasma chemical vapor deposition (CVD) method using H2 and CH4 as reactant gases under a chamber pressure of about 230 Pa. Without DC bias, only catalytic nanoparticles could be observed by field emission scanning electron microscopy (FE-SEM) on substrate surface after growth. Highly oriented and dense CCNFs could be deposited when a negative DC bias in the range of 150-230 V was applied to the substrate holder during growth. The average density of CCNFs was measured as being of the order of 1010 cm-2, while the average length was of the order of 102 nm, and the conical angle was in the range of 10-15°. The relationships between the density, the root diameter and the length of CCNFs are discussed.
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