Page 91 - Nanotechnology an introduction

Challenges that still need to be overcome include: matching the semiconductor band gap to the solar spectrum; matching the positions of the band
edges to the redox potentials of the desired chemical reactions; finding catalysts to facilitate the desired chemical reactions; preventing
photocorrosion (i.e., reduction or oxidation of the semiconductor by its own charge carriers).
7.10. Summary

A device is fundamentally an information processor or transducer. The types of devices considered in this chapter are mainly logic gates and
sensors. The relay is considered as the paradigmatical component of the logic gate, which is the foundation of digital processing hardware.
Ultraminiature devices based on electron charge as the carrier of information are considered. These include single-electron transistors, which are
scaled-down versions of conventional transistors; molecular electronic devices, in which organic molecules replace the inorganic semiconducting
media of conventional transistors; and quantum dot cellular automata. As these devices become very small, movement of electronic charge
becomes problematical and using electron spin as the information carrier becomes attractive. This includes both hybrid devices in which spin
controls electron current (the main application is for magnetic field sensing), and “all-spin” devices in which spin is also the carrier of information.
Photons may also be used as information carriers, although mostly not in the nanorealm, except for molecular photonics, which is, however,
covered in Chapter 11 because the only current example uses a biomolecule for the central function. Quantum computation, although not
specifically tied to the nanoscale, is briefly described as a completely different approach to increasing computational density, for which photonic
devices are well suited. Nanoscale mechanical devices are considered, both as relays and sensors. A brief survey of fluidic devices in the
nanoscale is given, including biosensors. Finally, nanoparticulate systems for the conversion of solar energy into fuels are considered.

7.11 Further Reading
Chua, L.O., Memristive devices and systems, Proc. IEEE 64 (1976) 209–223.
Ferry, D.K.; Akers, L.A., Scaling theory of modern VLSI, IEEE Circuits Devices Mag. (1997) 41–44.
Hutchby, J.A.; Zhirnov, V.; Cavin, R.; Bourianoff, G., Emerging nanoscale memory and logic devices: a critical assessment, IEEE Comput. Mag.
(2008) 78–82.
Jacak, L., Semiconductor quantum dots—towards a new generation of semiconductor devices, Eur. J. Phys. 21 (2000) 487–497.
Likharev, K.K., Single-electron devices and their applications, Proc. IEEE 87 (1999) 606–632.
Parkin, S.S.P.; Hayashi, M.; Thomas, L., Magnetic domain-wall racetrack memory, Science 320 (2008) 190–194.
Politi, A.; O'Brien, J.L., Quantum computation with photons, Nanotechnol. Percept. 4 (2008) 289–294.
Shibata, T., Computing based on the physics of nanodevices—a beyond-CMOS approach to human-like intelligent systems, Solid State Electron.
53 (2009) 1227–1241.