The state of matter changes from solid to liquid and then to gas as the temperature is raised. Further increase in temperature breaks Coulomb bondage between electron and nucleus and matter becomes ionized at temperature higher than about 10,000 K. (Even a candle flame at 1500 K is in the state of weakly ionized plasma as demonstrated by Faraday. Thermal ionization also occurs during reentry of spaceships into the atmosphere.) Fluorescent lamps, lightning, solar wind, magneto and ionospheres around the Earth, electrostatic arcing, and plasma TV are a few examples of plasma phenomena and applications.
The sun and all stars are in plasma state. The high temperature in the sun is maintained by heat released in nuclear fusion reactions whereby hydrogen ions are fused to form heavier nuclei. (Uncontrolled demonstration of fusion power was achieved in the form of hydrogen bomb.) Active research is being carried out worldwide in order to realize fusion reactors which would provide clean, abundant energy source for future generations.
Plasma technology is indispensable in modern manufacturing and electronics industries. Tiny computer chips smaller than 1 micron size can be fabricated on silicon substrate only in plasma reactors through the process of dry etching. Novel materials, such as carbon nanotubes and diamond semiconductors, can be synthesized in plasma reactors in which chemical reactions can be accelerated by non-thermal electrons. Flat plasma display (plasma TV) and plasma headlamp have reached the stage of commercial production after decades of basic research.