Biomedical Engineering Reference
In-Depth Information
(a)
(b)
1
µ
m
1
µ
m
(c)
50
Flat Si wafer
360-nm inverted pyramids
40
30
20
10
0
400
500
600
700
800
Wavelength (nm)
FIGURE 12.10
(a) SEM image of a templated chromium nanohole array using spin-coated non-close-packed monolayer
colloidal crystal as deposition mask.
(
b
)
SEM image of a 360-nm-sized inverted pyramidal array templated from 320-nm-
diameter silica spheres. (c) Specular optical reflectivity spectra at normal incidence. Black: bare (1 0 0) silicon wafer. Red: the
sample in (b). Reprinted with permission from
Appl Phys Lett
91
(2007), 231105. Copyright 2007, American Institute of Physics.
(For interpretation of the references to color in this igure legend, the reader is referred to the web version of this topic.)
wavelengths around 400 nm. This antireflection
performance is good but not outstanding. The
optical simulations based on a rigorous coupled-
wave approach (RCWA)
[130, 131]
indicate that
the limited antireflection performance of the
inverted pyramidal arrays is caused by the lim-
ited optical depth of the inverted pyramids. Due
to the characteristic 54.7° sidewalls, the depth of
the V-shaped inverted pyramids created by the
anisotropic wet etch is affected by the size and
separation of the templating spheres. To greatly
improve the antireflection performance of the
templated ARCs, the optical depth of the grat-
ings needs to be increased.
