Microwave discharges in liquids: fields of applications

The purpose of this review is to draw attention to the relatively new and poorly studied object of plasma physics, namely to the microwave discharges in liquids. Study of microwave discharges in liquids began only in early 2000-th and now they still remain one of the least studied plasma objects. Nevertheless, they are beginning to find application for solving various applied problems. This brief analytical review describes the results of studies on the use of such discharges in different applied areas: for water decontaminants, for generation of nanoparticles, for deposition of diamond coatings, for etching of photoresists, etc. Discharges can be created at pressure ranged from $0.1$ kPa to atmospheric pressure at microwave powers from tens of watts to several kilowatts. Known data on the use of microwave discharges show their high efficiency in comparison with conventional discharges in the gas phase and in comparison with discharges of other types in liquids. Place of microwave discharges in liquids among other types of discharges is analyzed.