The nanostructure and electrical properties of SWNT bundle networks grown by an 'all-laser' growth process for nanoelectronic device applications

We report on an 'all-laser' synthesis approach that permits the control of the lateral growth of single wall nanotubes (SWNTs) on SiO2/Si substrates at selected locations where nanoparticles catalysts were first deposited. This novel two-step growth process uses the same UV laser (KrF excimer; lambda = 248 nm) to deposit, in a first step, the CoNi nanoparticle catalysts on patterned SiO2/Si substrates and, in a subsequent step, to grow the SWNTs. Atomic force microscopy and micro-Raman spectroscopy revealed that the 'all-laser' process leads to the formation of horizontal random networks of SWNT bundles, that bridge two adjacent nanoparticle strips. The diameter of the SWNTs was found to be similar to1.1 nm, while that of the bundles is generally in the 10-15 nm range. The current (I)-voltage (V-SD) characteristics of the fabricated SWNT devices confirmed that the random networks of SWNT bundles exhibit a p-type field-effect transistor behaviour. Conductance (G)-gate voltage (V-G) curves not only demonstrated that transport through the bundle networks was dominated by positive carriers (holes) but also that the bundles consist of mixtures of semiconducting and metallic SWNTs. The extremely high efficiency of our 'all-laser' growth process in producing high-quality SWNTs together with its relative simplicity definitely open new prospects for the development and integration of novel architectures of nanodevices based on SWNT networks.