Inductively coupled plasma
An inductively coupled plasma (ICP) is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.
In planar geometry, the electrode is a length of flat metal wound like a spiral (or coil). In cylindrical geometry, it is like a helical spring. In half-toroidal geometry, it is toroidal solenoid cut along its main diameter to two equal halves.
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 field in the rarefied gas, leading to the formation of the figure-8 electron trajectories providing a plasma generation (see Hamilton-Jacobi equation in electromagnetic fields). Argon is one example of a commonly used rarefied gas.
Plasma electron temperatures can range between ~6 000 Kº and ~10 000 Kº (~6 eV - ~100 eV), comparable to the surface of the sun. 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 (HDP) is needed.
- ICP-AES, a type of atomic emission spectroscopy.
- ICP-MS, a type of mass spectrometry.
- ICP-RIE, a type of reactive-ion etching.
Another benefit of ICP discharges is that they are relatively free of contamination because the electrodes are completely outside the reaction chamber. By contrast, in a capacitively coupled plasma (CCP), the electrodes are often placed inside the reactor and are thus exposed to the plasma and subsequent reactive chemical species.
- A. Montaser and D. W. Golightly, eds. Inductively Coupled Plasmas in Analytical Atomic Spectrometry, VCH Publishers, Inc., New York, 1992.
- Pascal Chambert and Nicholas Braithwaite. "“Physics of Radio-Frequency Plasmas”". Cambridge University Press, Cambridge (2011). pp. 219–259. ISBN 978-0521-76300-4.
- Shun'ko, Evgeny V.; Stevenson, David E.; Belkin, Veniamin S. (2014). "Inductively Coupling PlasmaReactor With Plasma Electron Energy Controllable in the Range From ~6 to ~100 eV". IEEE Transactions on Plasma Science 42 (3): 774–785. doi:10.1109/TPS.2014.2299954. ISSN 0093-3813.