ESTIMATION OF DENSITY OF CHARGE SPECIES IN A TRIODE DISCHARGE SYSTEM

Triode discharges are widely used in plasma assisted physical vapour d eposition techniques to enhance ionisation even under low pressures. I n addition to this, the triode discharges enable independent control o f substrate bias currents irrespective of bias voltage and pressure, c ompared to magnetron discharges. One of the problems associated with t riode discharge is non-uniform distribution of plasma density. The ext ent of non-uniformity depends on the size of the chamber, characterist ics of the thermionic filament, location of the electrodes with respec t to one another, operating potentials at the electrodes, and pressure . Hence it is necessary to carry out the discharge studies to study sp ace charge distribution in the chamber. A Langmuir probe is used in th e present study, to estimate the density of ions and electrons for dif ferent triode discharge currents, substrate bias voltages, pressures a nd at different locations in the plasma in a triode ion plating system . It has been observed that the uniformity of the density of the charg e carriers depends on the operating conditions. (C) 1997 Elsevier Scie nce Ltd. All rights reserved.