Are dominant sputtering products from metal targets really monatomic?

We observed four experimental results which suggest the existence of unidentified species other than metal atoms and metal ions in magnetron sputtering discharges employing metal targets. The most probable species which are compatible with the experimental observations are clusters (mainly dimers and trimers) of metal atoms. According to the experimental results, it is speculated that the amount of clusters is comparable to that of metal atoms. In other words, the present experimental results suggest a possibility that dimers and trimers are major sputtering products from metal targets.