Antireflective Properties of Polystyrene Nanosphere Self-Assembled Films
V. CÂNPEAN, C. FARCĂU, E. VINŢELER, S. AŞTILEAN
Abstract. In this work we examined the antireflective properties, in
the visible and near-infrared (NIR) range, of polystyrene nanospheres
self-assembled films deposited on glass substrate by convective assembly.
For incident light of wavelength larger that the diameter of spheres, the
two-dimensional (2D) colloidal crystal cannot be resolved by the incident
light and the structure acts as a continuous film with graded refractive
index along the z-axis. In this case we found the film exhibits a clear
antireflective ef-fect. For incident light of shorter wavelength this is
not the case and the structure acts as a simple diffraction grating, the
incident light being distributed either into propaga-tive or
waveguided diffracted orders. We simulated the transmission and
reflectivity of such structures by using finite-difference time-domain (FDTD)
method and found good agreement with the measurements.