Magnetron sputtering plasmas are widely used for deposition of thin films in many industrial applications. Experiments conducted at Liverpool seek to diagnose the plasmas used in this context, so that the deposition process may be better understood. Though negative ion diagnostics are prevalent in other fields, the study of the significance of negative ions in magnetron sputtering applications has not been extensive. In this work, the laser photodetachment technique was employed to determine the spatial distribution of negative ions within typical reactive magnetron plasmas. Measurements were made in a capacitively-coupled dc discharge, with a source gas mixture of 80% argon and 20% oxygen. The focus of this work is the case of a 12 mTorr discharge with 200 W applied power. The laser used for this diagnostic is a frequency-doubled Nd: YAG (532 nm) with a pulse frequency of 10 Hz, and energy density per pulse of 246 mJ cm~(-2). This work was part-funded by the RCUK Energy Programme under grant EP/I501045 and the European Communities under the contract of Association between EURATOM and CCFE. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
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