Plasma Diagnosis and Modeling

For the understanding of plasma properties and for the control of a plasma reactor, it is important to detect electrons, ions, and other active species present in a plasma and to measure their densities. To this end, various methods have been developed, including measurements of radicals by absorption spectroscopy (Anderson et al, 1999) or optical-emission spectroscopy, measurements of electron densities and electric fields by probes, and measurements of ions by mass spectrometry (Matsuda et al, 1983 Robertson et al, 1983). In particular, neutral and nonemitting radicals (for instance, radicals in the electronic ground state) are expected to be abundantly present in a nonequilibrium plasma and have become measurable recently (Sugai et al., 1995 Cosby, 1993 Mi and Bonham, 1998 Motlagh and Moore, 1998). 

Progress in plasma monitoring with advanced methods of atomic, molecular, and optical physics, as exemplified above, has contributed greatly to plasmaprocessing technology, especially in improving the reproducibility of a treatment procedure. 

Method Object of measurement Limit of detection Spatial resolution Remarks 

Infrared laser absorption Neutral molecules (in the ground I0 -I0 cm- Good High sensitivity 

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