On-substrate growth of single-walled carbon nanotube networks by an “all-laser” processing route

We report on the process latitude of an “all-laser” approach for the controlled growth of single-walled-carbon-nanotube (SWCNT) mats at predefined locations on silicon substrates. Unlike the conventional laser ablation methods where the SWCNTs are produced in the soot form, from the concomitant ablation of a graphite target loaded with metal catalyst, the “all-laser” process proceeds in two consecutive and independent steps. Indeed, the same KrF pulsed laser is first used to deposit at room temperature, the Co/Ni catalyst nanoparticles (NPs) onto the substrates – of which size and surface density can be controlled by adjusting the number of laser ablation pulses – and subsequently to grow SWCNTs onto the Co/Ni NPs sites, from the laser ablation of a pure graphite target. The grown SWCNT networks are shown to be fairly controllable by choosing the appropriate ratio of “graphite to Co/Ni-NPs” laser ablation pulses. The Co/Ni NPs and the grown SWCNTs were systematically characterized by atomic force microscopy, scanning/tunnelling electron microscopy, Raman spectroscopy and thermogravimetry analysis, and their potential as an active material in thin film transistor was evaluated. Obtained characterization data have led to identify key growth parameters of this novel approach, and to propose growth mechanism models that best describe our observations.