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Luminescence - Porous Silicon

Science EncyclopediaScience & Philosophy: Linear expansivity to Macrocosm and microcosmLuminescence - Fluorescence And Phosphorescence, Processes That Create Luminescence, Thermoluminescence, Porous Silicon

Porous silicon

In the early 1990s, L. T. Canham at the Royal Signal and Radar Establishment in England reported luminescence from porous silicon. This generated great interest, because if the luminescence could be controlled, then light-emitting devices could be integrated with silicon microelectronics. Although silicon photodetectors had been made, the material had not been known to emit light before. This could lead the way to relatively inexpensive optical computers, signal-processing devices, and optical communications devices.

Debate about what process creates the light is divided: those who believe the light is emitted as part of a quantum confinement effect and those who believe that the light is the product of a chemical reaction between the silicon and oxygen. If the quantum confinement theory proves correct and the effect can be prolonged, then useful light-emitting devices could be made from porous silicon. If the chemical theory is correct, then the luminescent period is probably inherently short-lived and the material would not make good reusable devices. Although no one has published reports that definitely debunk one theory, the chemical theory is most popular at the moment because of the instability of porous silicon devices.


Resources

Books

Barkan, Joanne. Creatures that Glow. New York: Doubleday, 1991.

Gundermann, K.-D., and F. McCapra. Chemiluminescence in Organic Chemistry. New York: Springer-Verlag, 1987.

Hewitt, Paul. Conceptual Physics. New York: Prentice Hall, 2001.

Horowitz, Yigal S., ed. Thermoluminescence andThermoluminescent Dosimetry, Vol I and II. Boca Raton, FL: CRC Press Inc., 1984.

Periodicals

Canham, L. T. Applied Physics Letters. 57(1990) :1046.

Iyer, S.S., and Y.-H. Xie. "Light Emission from Silicon." Science 260 (April, 2 1993): 40-46.


Yvonne Carts-Powell

KEY TERMS

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Cathode ray tube or CRT

—A display device that includes an electron gun to produce a stream of electrons, magnets to direct the electrons to specific spots on the opposite end of the tube, and phosphors on the receiving end that absorb the electrons and glow briefly.

Decay time

—The length of time between when energy is introduced into a molecular system and when the system returns to equilibrium.

Fluorescence

—Luminescence that stops within 10–5 seconds after the energy source is removed.

Incandescence

—Light created by heating. Incandescence is not a luminescent process.

Phosphor

—A material that absorbs energy over some period of time, then gives off light for a longer period. Commonly used in CRTs.

Wavelength

—The distance between two consecutive crests or troughs in a wave.

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