Plasma biased potential

Two basic versions of the process plasma-based ion plating and vacuum-based ion plating. The coating material is vaporized in a manner similar to evaporation. Typically, the plasma is obtained by biasing the substrate to a high negative potential (5 kV) at low pressure. The constant ion bombardment of the substrate sputters off some of the surface atoms which results in improved adhesion and reduced impurities. Surface coverage of discontinuities is also improved. 

Positive ion data were monitored with a cylindrical Langmuir probe similar in design to that used in previous experiments (7). The probe circuitry was similar to that of Hand and Kistiakowsky (8). The probe was biased at voltages from —40 V to +40 V, and the resulting characteristic curve data were reduced following Calcote (9), in which the positive-ion saturation curve is extrapolated to the plasma potential to minimize the uncertainty in the collection area. 

To bombard growing films of electrically insulating materials from a plasma, the surfaces must either attain a high self-bias or must be biased with an rf or pulsed dc potential. 

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