Carbon nanoparticles grown in the subsurface-region of porous SiO2

Abstract

Carbon nanoparticles (CNPs) were grown in the subsurface-region of porous SiO2 templates that had been subjected to plasma enhanced chemical vapour deposition. The over-layer multiwall carbon nanotubes (MWCNTs) grown in the surface region of the template were removed by a sonication process. Mechanical scrubbing of the template surface was used to remove the subsurface for investigation. The powder obtained was dispersed in ethanol onto copper-grids for characterization by electron microscopy, electron diffraction and micro-Raman spectroscopy. Elliptical, faceted and grape-shaped CNPs were observed by electron microscopy with electron diffraction patterns showing short range orderings. The Raman spectrum of the CNPs was found to be distinctly different from that of the over-layer MWCNTs in that the D-band ( at similar to 1385 cm(-1)) merged with the G-band (at similar to 1552 cm(-1)). It seems that the CNPs in the subsurface-region grew simultaneously with the over-layer MWCNTs. A possible growth mechanism is proposed. The I - V characteristic of the CNPs, recorded by scanning tunnelling microscopy, was found to be asymmetric and characteristic of degenerately doped p - n junction diodes.