Biomedical Engineering Reference
In-Depth Information
(a)
(b)
1
µ
m
1
µ
m
7
(c)
Hexagonal array
Square array
6
5
4
3
2
1
0
400
500
600
700
800
Wavelength (nm)
FIGURE 12.13
Comparison of the specular optical reflection at normal incidence between (a) a square silicon array and
(b) a hexagonal silicon array patterned under the same conditions. Reprinted with permission from
J Vac Sci Technol B
27
(2009), 1043-1047. Copyright 2009, American Institute of Physics.
that the nanopillar ARC exhibits excellent broad-
band antireflection property, better than com-
mercial ARC on the crystalline silicon solar cell,
which shows reduced reflection only around
600-800 nm
[6]
.
commercial mc-Si wafers covered with close-
packed silica particles (
Figure 12.8
b)
[111]
.
Figure 12.15
a shows the typical top-view SEM
image of a templated moth-eye grating using
LB-assembled silica spheres as etching mask
during a Cl
2
-RIE process.
Figure 12.15
b com-
pares the specular hemispherical reflectance
obtained from a polished sc-Si wafer, a solar-
grade mc-Si wafer, and the templated mc-Si
grating. The flat sc-Si wafer exhibits 30-50%
12.3.1.3 Dry-Etched Multicrystalline Silicon
Moth-Eye Antireflection Coatings
The same dry-etch approach can also be uti-
lized to create broadband moth-eye ARCs on
