Inductively coupled plasma
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An inductively coupled plasma (ICP) is a type of plasma source in which the energy is supplied by electrical currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields. Image:ICP-small.jpg There are two types of ICP geometries: planar and cylindrical. In planar geometry, the electrode is a coil of flat metal wound like a spiral. In cylindrical geometry, it is like a helical spring.
When a time-varying electric current is passed through the coil, it creates a time varying magnetic field around it, which in turn induces azimuthal electric currents in the rarified gas, leading to break down and formation of a plasma.
ICP discharges are of relatively high electron density, on the order of 1015 cm-3.
As a result, ICP discharges have wide applications where a high density plasma is necessary.
Another benefit of ICP discharges is that they are relatively free of contamination because the electrodes are completely outside the reaction chamber. In a capacitively coupled plasma (CCP), in contrast, the electrodes are placed inside the reactor and are thus exposed to the plasma and subsequent reactive chemical species.
Applications
- ICP-AES, a type of atomic emission spectrometry
- ICP-MS, a type of mass spectrometry.
- ICP-RIE, a type of reactive ion etching.
References
A. Montaser and D. W. Golightly, eds. Inductively Coupled Plasmas in Analytical Atomic Spectrometry, VCH Publishers, Inc., New York, 1992.