Influence of the gas composition on the synthesis of boron-doped carbon nanotubes by ECR-CVD

Boron-doped carbon nanotubes (CNTs) were synthesized on porous silicon by electron cyclotron resonance chemical vapor deposition (ECR-CVD). CH4, B2H6 and H2 were used as the source gases and Fe3O4 nanoparticles as the catalyst. The effect of gas composition on the boron-doped CNTs growth characteristic was investigated. Scanning electron microscopy , transmission electron microscopy and X-ray photoelectron spectroscopy were used to evaluate the structure and composition. The results show that adding B2H6 influences the growth characteristic of CNTs greatly. CNTs tend to unaligned growth with boron. The increase of the B2H6 ratio leads to changes in the structure of CNTs from straight tubular to bamboo-like and makes the outer diameters bigger, the tube walls thicker, cause a rough surface and a decrease in the growth rate of the CNTs. An increase in the B/C ratio within the samples was detected as the B2H6 ratio in the precursor gas was increased.