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

• Published in: Surface & coatings technology 2011-01, Vol.205 (8), p.2755-2762
• Main Authors: Straňák, Vítězslav, Block, Stephan, Drache, Steffen, Hubička, Zdeněk, Helm, Christiane A., Jastrabík, Lubomír, Tichý, Milan, Hippler, Rainer
• Format: Article
• Language: English
• Subjects: AFM; AGGLOMERATION; Applied sciences; Cluster mass- and size- distribution; Clusters; Copper; Cross-disciplinary physics: materials science; rheology; Cu cluster growth; DEPOSITION; Discharge; Exact sciences and technology; Magnetron sputtering; Materials science; Metals. Metallurgy; MICROSTRUCTURES; Nanostructure; Physics; Production techniques; Pulsed magnetron sputtering; SPUTTERING; Surface treatment; Surface treatments; TUBE; Tubes
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2010.10.030

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 T g-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. ► Pulsed magnetron sputtering was used for size-controlled deposition of Cu clusters. ► Size of the clusters can be controlled by the frequency and duty cycle of pulses. ► Size of deposited clusters is observed about 10 5 amu and /or 8-10 nm in diameter. ► The cluster mass flux is not dependent on frequency or duty cycle.