Reduction of Short Wavelength Reflectance of Multi-wall Vertically Aligned Carbon Nanotubes Through UV Laser Irradiation
Michelle S. Stephens, Brian J. Simonds, Christopher S. Yung, Davis R. Conklin, David J. Livigni, Alberto R. Oliva, John H. Lehman
Multi-wall carbon nanotube coatings are used as broadband, low-reflectance absorbers for bolometric applications, blackbody radiators, and for stray light control. Irradiation of single wall carbon nanotubes with UV laser light has been shown to remove carbon impurities, but there have been few investigations of the interaction of UV light with the more complex physics of multi-wall carbon nanotubes has not been investigated. We present measurements of reflectance and surface morphology before and after exposure of multi-wall carbon nanotube coatings to 248 nm UV laser light. We show that UV exposure initially reduces the reflectivity at wavelengths below 600 nm. This effect can be used to tune the reflectivity of carbon nanotube absorber coatings used for broadband applications. It also provides a glimpse at the processes associated with environmental aging of these coatings, an aspect that is of importance in space applications. Finally, we find that the change in reflectance depends on the nanotube growth or deposition process.