Biomedical Engineering Reference
In-Depth Information
in the form of arrays to provide formation of any number of individual nanowires. The
procedure is a single-step deposition process for each nanowire, and multiple-nanowire
arrays of different materials can be deposited on the same wafer sequentially. PPY and
PANI were used as models for demonstration.
Figure 4.5 shows the SEM image of a 100 nm wide and 4
m long electrochemically grown
PANI nanowire. As observed, the nanowire was continuous, well-confined, and nondendrite,
spanning the entire length and making contact between the two electrodes. The ability to make
individually addressable nanowires in high density was evaluated by making two 200 nm
wide by 2.5
m long PPY nanowires separated by 6 µm sequentially as shown in Figure 4.6.
A complementary approach to the one reported above is based on CP nanojunctions
formed by bridging two electrodes separated with a gap of 1-100 nm with polymer and
was reported by Tao's group [41]. The process is started with an array of electrode (Au or
other materials) pairs, 1-100 nm apart, fabricated on an oxidized Si chip using either optical
lithography or electron beam lithography
(
Figure 4.7a
)
. The gap between the Au electrodes is
then reduced down to
1 nm by first electrochemically depositing Au onto the electrodes
(
Figure 4.7b
)
. This causes an increase in the current flowing across the gap, due to quantum
Polyanilne NW
Cathode
(+)
Anode
(
−
)
FIGURE 4.5
SEM image of a 100 nm wide by 4
m long
polyaniline (PANI) nanowires [39]. (From
Ramanathan, K., Banger, M. A., Yun, M., Chen,
W., Mulchandani, A., Myung, N. V. (2004).
Individually addressable conducting polymer
nanowires array.
Nano Lett
. 4:1237-1239. With
permission.)
Acc.V
10.0 kV 3.0 10000x SE 21.4
Spot Magn
Det WD
5
µ
m
Anode
(
−
)
Cathode
(+)
FIGURE 4.6
SEM image of two 200 nm wide by 2.5 µm long
polypyrrole (PPY) nanowires separated by 10
µm deposited one at a time [39]. (From
Ramanathan, K., Banger, M. A., Yun, M., Chen,
W., Mulchandani, A., Myung, N. V. (2004).
Individually addressable conducting polymer
nanowires array.
Nano Lett
. 4:1237-1239. With
permission.)
Anode
(
−
)
Cathode
(+)
PPY Nanowires
