Biomedical Engineering Reference
In-Depth Information
FIGURE 1.7
Examples of silicon nanowires in junctionless transistors. (Reprinted with permission from
Alagarasi, A. 2011.
Introduction to Nanomaterial
. National Centre for Catalysis Research.)
The field of NM development assists the industry in breaking down these barriers by offering the
manufacturers with nanocrystalline forms of starting materials; ultra-high-purity materials; materi-
als with improved thermal conductivity; and prolonged, durable interconnections in microproces-
sors (Figure 1.7).
As a component of a circuit, a decrease in the size of the transistor can contribute to a decrease
in the overall size. The transistor's design consists of a heavily doped source of electrons, the gate,
and the drain that is
p
-doped with holes that can take up electrons (Alagarasi 2011). Conventional
inversion-mode (IM) transistors suffer from a few drawbacks that limit the reduction in size and the
speed of operation as a function of the material's doping concentration.
The use of nanotechnology in computer engineering has allowed for the design of junctionless
transistors, which are substantially more effective and much smaller in size as compared to the IM
device. In the junctionless transistor, the doping concentration is equal to that on the source and drain.
The gate, controlling the current and acting as a drain, is split from the nanowire by a thin, insulating
layer. If the cross section of the device is small enough, the gate can deplete the heavily doped material
completely, turning the current off (Lee et al. 2009). Also, as the function of the current is controlled
exclusively by the gate, the lifetime, temperature, and efficiency of the device are greatly improved.
1.4.3
e
NvIroNMeNtal
a
pplIcatIoNs
1.4.3.1 Catalysis and Elimination of Pollutants
Owing to their highly reactive surface, NPs make great catalysts (Bell 2003). Aluminum powder
and NPs used as a solid fuel in rocket propulsion are examples (Miller and Herr 2004, Risha et al.
2002). For comparison, bulk aluminum is largely unreactive and is extensively used in utensils. The
differences in reactivities between the two forms of aluminum can be easily explained by the fact
that catalysts supporting or retarding the reaction rates are dependent on surface activity, which can
be very important in manipulating the rate-controlling step (Alagarasi 2011).
This catalytic, chemical activity in NMs can be used in reactions of toxic gases, such as carbon
monoxide and nitrogen oxide, in automobile catalytic converters, and in power generation equip-
ments to decrease the hazards and pollution from combustion products (Alagarasi 2011, Astruc
2008, Haruta 2002).
