Direct laser writing of carbon nanotubes (Conference Presentation)

Carbon nanotubes (CNTs) have been expected for applications in many future electronic devices. To fabricate CNT structures on substrates, several techniques such as spray coating, spin coating and vacuum filtration have been proposed so far. In this work, we report a very simple and efficient method to deposit CNTs on a glass substrate by only scanning a focused light in CNT dispersion. This fabrication technique can provides a bottom up method for the deposition of CNTs in arbitrary shape on the substrate. We placed the dispersion of single-walled carbon nanotubes (SWCNTs) on a glass substrate. From the back side of the substrate, a laser (λ=975 nm; 100 mW) was focused on the interface between the substrate and the SWCNT dispersion by an oil immersion objective lens (Nikon 100X 1.25NA). Once the focal spot of the light is in focus on the substrate, it began to deposit SWCNTs around the spot (~1 um). Then, the linewidth of the deposition of SWCNTs was approximately 30um, and its electrical conductivity was 12.5 S/cm. We measured the Raman spectrums of the SWCNT dispersion and the deposited SWCNTs. Their G/D ratios were the same value, which indicated that any lattice defects were hardly occurred to SWCNTs in this process. Hence, this method can be useful application for fabrication processes of a variety of CNT devices. We have built the prototype of CNT field-effect transistors. In this presentation, we will show that a collimated light instead of the focused light can be applicable also.