Effects of randomness and inclination on the optical properties of multi-walled carbon nanotube arrays

Abstract

The optical properties of multi-walled carbon nanotube arrays are investigated using the finite-difference time-domain method, focusing on the effects of various structural randomness, including random position, diameter, length, and orientation. It is found that the arrays with random position, diameter, length, and small inclination angle have quite small absorption enhancement compared to the ordered arrays. The reflection spectra of the arrays with random position, diameter, and small inclination angles are almost identical to the ordered array, but large reflection suppression is seen in vertical arrays with random length. For oblique arrays, the absorptance increases with inclination angle for S-polarized light, but weakly depends on inclination angle for P-polarized light. By comparing the inclined arrays with different volume fractions, the reflectance is found to be largely determined by the local volume fraction of the top surface of carbon nanotube arrays.