Catalyst deposition and carbon nanotubes synthesis by laser-assisted chemical vapor deposition

Dispersed nickel sulphate (NiSO₄) micro-clusters on Si substrates were disintegrated by pulsed excimer laser irradiation. At proper fluences, the NiSO₄ clusters were pulverized into nanoparticles. The size ranges and distributions of fragments and/or particles were found to be dependent on excimer laser fluence and laser pulse number. Both CO₂ laser chemical vapor deposition (LCVD) and hot-filament chemical vapor deposition (HFCVD) were used for catalytic growth of carbon nanofibers (CNFs)/carbon nanotubes (CNTs) using excimer laser irradiated NiSO₄ catalysts. For catalysts prepared using excimer laser irradiation at fluences of 100 and 200 mJ/cm², CNFs were dominant products. These CNFs were grown radially out of large NiSO^ clusters, forming dendritic CNFs bunches. For catalysts prepared using excimer laser irradiation at 300 mJ/cm², multi-walled CNTs with highly-uniform diameters were obtained. Catalysts preparation with excimer laser disintegration of dispersed NiSO₄ compound is a simple, ultrafast and in-air process.