Estimation of density of charge species in a triode discharge system

Triode discharges are widely used in plasma assisted physical vapour deposition techniques to enhance ionisation even under low pressures. In addition to this, the triode discharges enable independent control of substrate bias currents irrespective of bias voltage and pressure, compared to magnetron discharges. One of the problems associated with triode discharge is non-uniform distribution of plasma density. The extent of nonuniformity depends on the size of the chamber, characteristics of the thermionic filament, location of the electrodes with respect to one another, operating potentials at the electrodes, and pressure. Hence it is necessary to carry out the discharge studies to study space charge distribution in the chamber. A Langmuir probe is used in the present study, to estimate the density of ions and electrons for different triode discharge currents, substrate bias voltages, pressures and at different locations in the plasma in a triode ion plating system. It has been observed that the uniformity of the density of the charge carriers depends on the operating conditions