Size-controlled formation of Cu nanoclusters in pulsed magnetron sputtering system

作者：Stranak Vitezslav^*; Block Stephan; Drache Steffen; Hubicka Zdenek; Helm Christiane A; Jastrabik Lubomir; Tichy Milan; Hippler Rainer

来源：Surface and Coatings Technology, 2011, 205(8-9): 2755-2762.

DOI：10.1016/j.surfcoat.2010.10.030

• Cu cluster growth
• Pulsed magnetron sputtering
• Cluster mass- and size- distribution
• AFM

Size-controlled Cu clusters are formed in a system which combines pulsed magnetron sputtering and gas condensation at room temperature. The discharge repetition frequency (0.1-25 kHz) and the duty cycles (20-90%) of the magnetron sputtering are varied systematically, the influence of discharge current (100-800 mA) and the pressure in the condensation tube (25-90 Pa) is also investigated. The cluster mass is determined by a quadrupole mass filter in the aggregation tube, and the cluster size by atomic force microscopy (AFM) imaging of deposited clusters. For all preparation conditions, the cluster mass shows a log-normal distribution. A non-monotonic frequency dependence with a maximum at 1 kHz and 20% of duty cycle is observed (about 10(5) amu, or cluster diameter 8-10 nm). By adjusting discharge frequency and duty cycle, the cluster mass can be decreased by one order of magnitude. We suggest that this effect is caused by energy dissipated into the aggregation tube; and find a critical buffer gas temperature Tg-cr which limits cluster growth. This view is supported by the constant cluster mass flux which does not change on variation of discharge repetition frequency or duty cycle. This feature indicates mass conservation.

• 出版日期2011-1-25