Time Resolved Langmuir Probe Characterisation of Reactive Pulse Magnetron Sputtering of MgO Thin Films

Abstract

A time resolved Langmuir double probe technique is presented, which is applied to a pulsed magnetron discharge at several hundred kilohertz used for MgO deposition. The probe was positioned on the symmetry axis of the circular magnetron. The time resolved measurement was done by fixing the probe voltage and recording the probe current as a function of time. This was repeated for different voltages. Then, the matrix of the I_U(t) curves was transposed with a computer to yield the usual I(U) characteristic for each time step, from which the plasma density and electron temperature were determined. After proper correction of the measured I_U(t) curves, consistent results are obtained. In particular, a characteristic time dependence of the charge carrier density during the ‘pulse on’ time including a sequence of maximum and minimum values was found. This characteristic temporal evolution of the charge carrier density depends on the pulse frequency and duty cycle. Similar structures in the electron temperature are only observed when the probe is placed near the magnesium target. SE/510