Biomedical Engineering Reference
In-Depth Information
Figure 15.10
(a) Schematic representation of nanocuboid array SERS
device. (b) Panoramic SEM image of 4
×
4 SERS substrate. In the inset, a
zoomed SEM image of 4
×
4 nanocuboid device is also demonstrated.
and acquisition time 20 s) and 150
objective (NA 0.95). The
spectral resolution of the instrument was about 1.1 cm
−
1
.R6G
molecules (1
μ
M) were chemisorbed over the device as a Raman
probe for the SERS enhancement investigations.
Au nanocuboid arrays with various edge sizes from 40 to 70 nm
were fabricated by EBL in step of 5 nm. Normal-incidence SEM
images were acquired on the fabricated samples. Figure 15.10a
shows the schematic representation of the cuboid nanostructures
with edge size, 'L' and interparticle separation 'D'. In particular, SEM
image of 4
×
4 arrays with
L
=
70 nm and
D
=
20 nm is reported
in Fig. 15.10b. Reference Raman measurements were carried out on
Au markers, fabricated on the same substrate.
In order to investigate the electric field distribution for
nanocuboid structures, theoretical calculations were performed. In
particular, the gold nanocuboids were designed to resemble the
fabricated structures and comparative simulations were performed
usingCSTsoftware,keepingallsimulationparametersequalinboth
cases. Electric field distribution on both kinds of structures are
shown in Fig. 15.11. It can be observed that the SPs were focused
at the opposite corners of the nanostructures. In addition, it is also
found that the electric field reaches up to about 26 V/m for sharp
edge cuboidstructure against about 10 V/m for truncated cuboid.
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