Decrease in reflectance of vertically-aligned carbon nanotubes after oxygen plasma treatment

Oxygen plasma treatment was used to lower the reflectance of multiwall vertically-aligned carbon nanotubes (VACNT). Specular reflectance measurements at an incident angle of 65° from normal show a decrease in reflectance over the wavelength range of 250-2500 nm, with up to 5 times lower reflectance at long wavelengths. Total hemispherical reflectance measurements show a decrease in reflectance from 300-2400 nm, with up to 8 times lower reflectance at short wavelengths. Etch rate measurements and helium ion microscopy reveal that the oxygen plasma reduces the reflectance of VACNT by modifying the surface morphology, characterized by etching away the top layer and inducing agglomeration of nanotube tips.