nanoscience and society - IAP/TU Wien

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466 Nanoelectronics
'he first is the bottom-up apscenario,
the chemical properties
of the material are utilized to assemble into a useful
structure. Scientists have shown through computational
schemes that self-assembled components can be arranged
into gears and mechanical structures. The energy needed
to move the components is provided through the potential
energy, or electrostatic energy provided at the tips of
the movable components.
The second approach to building NEMS devices is
called the top-down approach, which uses fabrication
techniques utilized in the MEMS and electronic industry,
such as optical and electron beam lithography.
These techniques suffer from the lack of necessary resolution
necessary for NEMS devices. Most known NEMS
devices built using the top-down approach integrate nanoscale
components, such as carbon nanotubes, to make
transistors that can be integrated into miniaturized actuators,
such as motors or pumps, that can perform a
physical work. Conventionally, the output of an electromechanical
device is the movement of a mechanical element.
These motions can be expressed as a deflection in
the mechanical component, linear motion, or rotational
motion of the mechanical components. Vibrational motion,
from a change in the amplitude or the frequency of
the vibration, also constitute an output of the electromechanical
device. Detection of these changes is recorded by
highly sensitive transducers.
Motion of small components can be induced by an
applied electric field and can be observed by optical interference
or angular deflection of laser beam. Both static
displacements and dynamic resonant motion can be
actuated and detected using this technique. A recently
demonstrated technique uses a scanning tunneling microscope
(STM) as an actuator and a scanning electron
microscope (SEM) to detect the motion.
In addition to enhancements in electronic and computational
power as a result of the development of
NEMS, it is anticipated that molecular displacements
and forces will be detected using future NEMS devices.
The possibility of engineering structures that can interact
and probe materials at the molecular levels will open
a new era for scientists to explore material characteristics
at the molecular level. NEMS devices are expected
to advance applications, such as the creation of ultrahigh
density data storage, sensitive and portable chemical
and biological sensors, and high-frequency device
components for wireless communication. Resonators
with frequencies above 10 GHz can now be built using
nanolithography techniques. As a result, the sensitivity
of the NEMS devices is orders of magnitude higher than
bulk and micro devices. Due to their small size, NEMS
devices dissipate very small amounts of energy.
A class ofNEMS devices that integrates the sensing or
actuation in a fluid environment has recently emerged
as a new area of NEMS. In the nanofluidic systems, the
diffusion and particle interaction with the fluidic surface
become dominant. New analytical systems that integrate
the actuation and sensing on a single chip have
recently emerged for biological and chemical evaluation
of markers. It is anticipated that in the near future,
NEMS devices will be made that can rapidly and reliably
detect a single molecule.
See Also: Electronics and Information Technology; Microscopy,
Electron (Including TEM and SEM); Microscopy, Scanning
Tunneling; Nanoelectronics; Nanomaterials; Nanoscale
Science and Engineering.
Further Readings
Cao, Guozhong and C. Jeffrey Brinker, eds. Annual Review
of Nano Research. Singapore: World Scientific Publishing
Company, 2008.
Dupas, Claire, P. Houdy, and M. Lahmani, eds. Nanoscience:
Nanotechnologies and Nanophysics. New York: Springer­
Verlag, 2006.
Hahn, Horst, Anatoli Sidorenko and Ion Tiginyanu, eds.
Nanoscale Phenomena: Fundamentals and Applications
(NanoScience and Technology). New York: Springer, 2009.
Wolf, Edward L. Nanophysics and Nanotechnology: An Introduction
to Modern Concepts in Nanoscience. Hoboken, NJ:
John Wiley & Sons, 2006.
Yousef Haik
Center for Research Excellence in Nanobiosciences
Nanoelectronics
University of North Carolina at Greensboro
The term nanoelectronics refers to electronic devices with
dimensions of functional elements below 100 nanometers
in size. The prefix nanG comes from the Greek word
nanos, meaning "dwarf." The term nanG in more technical
terms means 10- 9 or one-billionth of something. One