We quantitatively assessed the influence of reactive gases on the formation processes of transition metal clusters in a gas aggregation cluster source. A cluster source based on a 2 in. magnetron is used to study the production rate of titanium and cobalt clusters. Argon served as working gas for the DC magnetron discharge, and a small amount of reactive gas (oxygen and nitrogen) is added to promote reactive cluster formation. We found that the cluster production rate depends strongly on the reactive gas concentration for very small amounts of reactive gas (less than 0.1% of total working gas), and no cluster formation takes place in the absence of reactive species. The influence of discharge power, reactive gas concentration, and working gas pressure are investigated using a quartz micro balance in a time resolved manner. The strong influence of reactive gas is explained by a more efficient formation of nucleation seeds for metal-oxide or nitride than for pure metal.

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A comparison of quadrupole mass spectrometric (QMS) and transmission electron microscopic (TEM) characterization of silver nano-cluster deposition produced by a nano-cluster source consisting of a planar DC magnetron sputter source in a high pressure gas aggregation chamber is presented and discussed. Cluster sizes and size distributions detected by the two different techniques are compared and the differences are discussed. The effects of He to Ar ratio, gas flow and magnetron power on the cluster size distribution are evaluated. The influence of the target erosion and aging effects are mentioned, too.

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