Experimental Investigation of Nanosecond Laser Ablation of Carbon Nanotubes

Carbon nanotubes (CNTs) have been a subject of development and investigation in the last two decades due to their superior physical and chemical properties, such as high electrical conductivity, high thermal conductivity, high mechanical and elastic properties, and relative inexpensiveness. This paper aims to grow CNTs in the lab and then investigate its manufacturability and relevant properties changes using the laser ablation process. The CNTs were grown using Chemical Vapor Deposition (CVD) process. The catalyst used for the growth was Iron on a Silicon substrate. The average size of the substrate samples is 5 mm by 5 mm. Continuum Surelite Class III laser with 1064 nm wavelength of single pulse mode is used to ablate the CNTs to assess property changes in CNTs resulting from laser-matter interaction. The laser beam energy and beam diameter are varied to investigate their influences on properties changes in CNTs. The laser beam energy ranges from 0.063 J to 0.35 J and the beam diameter is adjusted using an optical lens, for which the focal length is 150 mm. Twelve samples have been tested and Scanning Electron Microscopy (SEM) and Raman Spectroscopy have been used to characterize the samples before and after laser ablation. A Raman spectrum was taken 4 to 6 times for each of the samples before the ablation. The density of the population for both SWCNTs and MWCNTs is demonstrated on the spectrum. It is found that when 0.153 J is used with the distance between sample and lens being equal to the focal length of the lens, SEM imaging and Raman Spectrum show a bright burned circumference caused by the laser beam. The CNTs at a distance of 200 micrometers around are found to be broken down as well due to the heat propagation from the laser beam. The application of laser can be used to reduce the electrical conductivity from a CNT network without damaging silicon substrate, which could expand the application of CNTs in the Electronics industry.