The development of technologies for plasma modification of surfaces is in large part based on controlling plasma sources to deliver desired fluxes of radicals and ions to surfaces. Doing so ultimately rests on the ability to control the energy and velocity distributions of charged and neutral particles. Controlling electron energy distributions, f(e), ultimately specifies the production rates of radicals and ions. Controlling the velocity distributions, f(v), of ions and neutrals ultimately specifies the activation energy delivered to surfaces. There has been an evolution of techniques to control f(e) and f(v) utilizing type of excitation (e.g., ICP vs CCP), frequency, pulse power and, most recently, multiphase plasmas These techniques are being challenged to provide the specificity required for nano-scale processing, particularly given the synergistic and presently uncontrolled relationship between fluxes into and returning from surfaces. Control of f(e) and f(v) becomes even more challenging in biological applications of plasmas and plasma medicine, typically performed at atmospheric pressure, where timescales for plasma formation are shorter than conventional control techniques can address. In this talk, techniques to control f(e) and f(v) in plasma sources in the context of plasma modification of biological and nano-scale surfaces will be discussed. Examples of control techniques will be taken from using pulsed, multi-frequency and multi-phase plasmas. Applications will be discussed from nano-scale cleaning and sealing of porous dielectrics; and dielectric barrier discharge treatment of wounded skin. Challenges facing researchers in developing plasma sources having the ability to control f(e) and f(v) will be discussed.

* Work supported by the Department of Energy Office of Fusion Energy Sciences, Semiconductor Research Corp., Applied Materials, Tokyo Electron., Agilent, Inc.