Microwave plasma
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Microwaves, being high frequency electromagnetic radiation in the GHz range, are capable of exciting electrode-less gas discharges.
Microwave-excited plasmas have two appealing properties: If applied in surface-wave-sustained mode, they are especially well suited to generate large-area plasmas of high plasma density. In addition, both in surface-wave and resonator mode, they can exhibit a high degree of spatial localisation. This allows to spatially separate the location of plasma generation from the location of surface processing, see afterglow plasma. Such a separation, together with an appropriate gas flow scheme, may help reduce the negative effect that particles released from a processed substrate may have on the plasma chemistry of the gas phase.