Lateral growth of single-walled carbon nanotubes across electrodes and the electrical property characterization

To realize the commercialization of single-walled carbon nanotube (SWNT)-based nanoelectronic and optoelectronic devices, the development of a fabrication process of catalytic chemical vapour deposition (CCVD) growth of SWNTs across electrodes is required. In this work, we report on the process of the lateral growth of SWNTs across catalytic pads. Using the conventional photolithography technique followed by thin film evaporation and lift off, the catalytic pads were prepared, consisting of nickel (Ni) and silicon dioxide (SiO₂) double layers, on the thermal silicon oxide substrate. The SWNTs were laterally grown across the catalytic pads in a thermal pyrolysis CVD system at 800–900 °C fed with a mixed gas flow of methane (CH₄) and hydrogen (H₂). The SiO₂, as the upper layer on Ni pads, not only plays a role as a barrier to prevent vertical growth but also serves as a porous medium that helps in forming smaller nano-sized Ni particles, so that the use of ultrathin Ni film would not be necessary for growth of SWNTs. Lateral growth across pads of various inter-spacing up to tens of microns was conducted for devices of different applications. The characterization by micro-Raman spectroscopy, atomic force microscopy and electron microscopy revealed the structure and diameters of the SWNTs and most importantly the SWNT density controlled by changing growth temperature. Following SWNTs growth, post-definition of metallic electrodes was conducted and the electrical properties were also measured.