When Plasmas Meet Phase Boundaries

Many applications of low temperature plasmas involve interactions with phase boundaries. A phase boundary is a transition from the gas phase to a solid or liquid or, in the most general of interpretations, transitioning into a gas with significantly different transport properties. These phase boundaries extend from hard, smooth solid surfaces to soft polymers and organic tissue, to liquids. The phase boundaries may be internal to the plasma as with particles or droplets being surrounded by the plasma. The boundaries may be passive (perhaps only charging) or active (chemically or physically reactive, as in sputtering). A brief overview of the variety of plasma-phase boundary interactions will first be given – sputtering, adsorption, desorption, etching, deposition, solvation, secondary emission. Synergistic interactions between materials processing plasmas with phase boundaries will then be discussed using results from computational investigations for low pressure systems (microelectronics fabrication), high pressure systems (functionalization of materials) and reactive systems (plasma-liquid).