Chemical sciences

A simple method for the synthesis of multiwall carbon nanotubes (MWCNTs) in the form of layers deposited on a silicon substrate is described. The method of chemical vapour deposition (CVD) was applied. The substrates were silicon wafers. Ferrocene in its solid form was used as the catalyst precursor. The sublimating ferrocene formed a thin layer of carbon and iron on the surface of the silicon. The source of carbon for the growth of the nanotubes was acetylene.

However already during the ferrocene deposition process on a silicon substrate, without the use of acetylene, the formation of single MWCNTs was observed. In the next stages, with the use of acetylene, reproducibility of the MWCNTs synthesis process with different degrees of coverage of the silicon substrate and different heights of the nanotubes layer was obtained.

The highest efficiency was obtained in the zone located at a distance of 27–30 cm from the catalyst at a temperature of 683–693 °C. The formation of the catalytic layer and the sequent stages of the growth of carbon nanotubes were observed and discussed. The D' band at 1600 cm^-1 was observed in the Raman spectra of the selected samples. This band is attributed to Stone-Wales defects. Those are atomic-scale defects in graphene layers alter the physical and chemical properties of carbon nanostructures. This indicates that the method used causes additional defects in the structure of carbon nanotubes.