Growth of carbon nanotubes on Si/SiO2 wafer etched by hydrofluoric acid under different etching durations

The preparation of SiO2 nanoparticles for the metal-free catalyst growth of carbon nanotubes (CNTs) was investigated. SiO2 nanoparticles were generated by etching Si/SiO2 wafers with 48–50% hydrofluoric acid. Etching duration was varied to study its effects on the generation of the SiO2 nanoparticles. Atomic force microscopy characterization showed that etching at 1 min was the most effective considering the significant numbers of SiO2 nanoparticles obtained under this condition. The wafer etched at 1 min after chemical vapor deposition at 900 °C for 1 h demonstrated a low ID/IG from Raman analysis which establishes that CNTs with highly ordered graphitic structures were grown. Raman analysis also showed a strong radial breathing mode peak in the low-frequency range for the substrate following the 1 min etching process after the reaction.