Plasma medicine Plasma medicine Plasma medicine is an emerging field that combines plasma physics, life sciences and clinical medicine. It is being studied in disinfection, healing, and cancer. Most of the research is in vitro and in animal models. It uses ionized gas (physical plasma) for medical uses or dental applications . Plasma, often called the fourth state of matter, is an ionized gas containing positive ions and negative ions or electrons, but is approximately charge neutral on the whole. The plasma sources used for plasma medicine are generally low temperature plasmas, and they generate ions, chemically reactive atoms and molecules, and
Depletion region the bulk semiconductor, then a spontaneous depletion region forms if the gate is electrically shorted to the substrate, in much the same manner as described for the p–n junction above. The principle of charge neutrality says the sum of positive charges must equal the sum of negative charges: where "n" and "p" are the number of free electrons and holes, and formula_28 and formula_29 are the number of ionized donors and acceptors "per unit of length", respectively. In this way, both formula_28 and formula_29 can be viewed as doping spacial densities. If we assume full ionization and that formula_32, then: