Modulated rf discharges as an effective tool for selecting excited species

Modulated NH3-fed rf glow discharges have been investigated; the emissions of the active species NH* and N-2* have been collected during the modulation period (time on+time off). In this study, modulated discharges have been characterized by a constant time on of 7 ms and a tunable time off in the range of 0-1000 ms. It has been found that the power modulation represents an effective tool for selecting excited species: this procedure may be exploited in surface grafting treatments of polymers where high selectivity of chemical groups is requested, e.g., for preferentially grafting -NH2 groups onto polyethylene with respect to all other N-containing functionalities. (C) 1999 American Institute of Physics. [S0003-6951(99)03827-9].