Biomedical Engineering Reference
In-Depth Information
CHAPTER
12
Biomimetic Antireflection
Surfaces
Blayne M. Phillips and Peng Jiang
Department of Chemical Engineering, University of Florida,
Gainesville, FL 32611, USA
Prospectus
The compound eyes of moths are composed by
hexagonal arrays of non-close-packed nipples that
exhibit low reflectance. The outer surface of the
cornea of a moth consists of periodic arrays of coni-
cal protuberances, termed corneal nipples, typically
of sub-250 nm height and spacing. These arrays of
subwavelength nipples generate a graded transition
of refractive index, leading to minimized reflection
over a broad range of wavelengths and angles of
incidence. In this chapter, the fabrication, charac-
terization, and modeling of moth-eye antireflection
coatings on both transparent substrates (e.g., glass)
and semiconductor wafers (such as crystalline silicon
and GaAs) are discussed.
12.1 INTRODUCTION
Antireflection coatings
(ARCs) are typically optical
films that are used on lenses and optoelectronic
devices to reduce light reflection and mitigate its
detrimental effects. ARCs are extensively utilized
in applications where the transmission of light
through an optical medium needs to be maxi-
mized, such as eliminating the ghost images for
flat-panel displays, increasing the transmittance
of optical lenses, reducing glaring from automo-
bile dashboards, and enhancing the conversion
efficiency of solar cells
[1-3]
.
12.1.1 Traditional Quarter-Wavelength
Antireflection Coatings
ARCs rely on two criteria: material refractive
index and film thickness. Optical reflection
from surfaces is largely governed by the differ-
ence in refractive indices at material interfaces.
The amount of reflection can theoretically be
calculated by using the Fresnel equation
[4]
.
Keywords
Antiglare coating, Antireflection coating, Bioinspi-
ration, Broadband, Close-packed, Colloidal crystal,
Crystalline silicon, GaAs, GaSb, Moth-eye surface,
Nanopillars, Photovoltaics, Rigorous coupled-wave
analysis, Self-assembly, Self-cleaning, Solar cells, Sub-
wavelength, Superhydrophobic coatings, Template,
Thin-film multilayer model
