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.
There are two types of ICP geometries: planar and cylindrical. 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.
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 rarefied gas, leading to the formation of a plasma. Argon is one example of a commonly used rarefied gas.
Plasma temperatures can range between 6 000 K and 10 000 K, 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 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.