Time-resolved characterisation of pulsed magnetron discharges using Langmuir probes

With the increasing popularity of pulsed plasma discharges, a growing interest in time-resolved process characterisation arose. Langmuir single and double probes enable one to determine plasma density and electron temperature as well as (in case of single probes) the plasma potential. Owing to the dimensions of the probe tips (typically 1–10 mm), a certain spatial resolution can be achieved. During the past years, few groups have done time-resolved Langmuir probe investigations of pulsed magnetron discharges. After a short review of this work, our own results of a time-resolved Langmuir double probe technique are presented which was applied to a reactive pulsed magnetron discharge at several hundreds of kilohertz used for MgO deposition. The method of the time-resolved probe technique and magnetron sputter system and power supply are briefly sketched. From the I(U) characteristics, the charge carrier density dependence on the time within the pulse is obtained. These results are discussed in connection with the discharge characteristics as well as time-dependent processes in the plasma which may lead to typical structures being observed.