Page 141 - Science at the nanoscale

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June 9, 2009
6.3. Quantum Dots, Quantum Wires
X
∆E
(a)
3
2
1
4
(b)
Energy level diagram of the single electron transistor.
Figure 6.13.
QUANTUM DOTS, QUANTUM WIRES
6.3
In this final section, we describe some common methods of
synthesizing low dimensional nanostructures. In general, the 131 ch06
approaches adopted to fabricate nanostructures can be classi-
fied into top-down and bottom-up methods. In the top-down
approach, the size of bulk materials is gradually reduced to the
nanometre scale by using etching techniques with the help of var-
ious lithography techniques. This method has proven to be a great
success in the highly developed semiconductor industry. On the
other hand, the bottom-up method utilises the self-assembly of
basic building blocks into nanostructures and such a process can
be controlled by the growth dynamics. Depending on the form of
the building blocks, the bottom-up method can be further divided
into solution-based or vapour-based routes.