Ion formation in thermionic-emission-assisted hot magnetron sputtering discharge

Abstract We report an abrupt Nb ion formation in a direct current hot magnetron sputtering discharge as a result of target temperature increase to a certain point (1900 K in our case). The effect is explained by a significant thermionic emission from the target surface, leading to an enhanced electron impact ionization in plasma volume. The phenomenon is especially pronounced for Nb (refractory metal), for which higher target temperatures can be reached. The volume density mapping is undertaken for Nb neutrals and ions (by laser-based spectroscopy), emphasizing the found effects.