Abstract
The synthesis of nanostructured materials was pioneered by the inert gas condensation and compaction technique. Most of these experiments used resistive heating in order to evaporate a material into an inert gas atmosphere (typical pressure ≈ 1 mbar He). We investigate sputtering as an alternative processing route in comparison to thermal evaporation. Sputtering has the advantage that refractory metals as well as compounds, e.g. oxides, can be synthesized, which is impossible or uncontrollable in the case of thermal evaporation. We have studied the conditions under which the sputter process results in the formation of nanostructured particles rather than granular thin films. Cu, Pd and W were sputtered at systematically varied process parameters of Ar-gas pressure, source-substrate distances and source power. The sputtered material was investigated by means of transmission electron microscopy. The morphology was determined from the bright-field images and the particle size distribution was evaluated from the dark-field micrographs. Particle formation was found to correlate with the above-mentioned parameters. The relationship between the size of the particles (typically 4–18 nm) and the process parameters is reported. Small-sized particles ( ⪕ 15 nm) exhibit a log-normal particle size distribution. Finally we discuss the formation mechanism of the sputtered particles.
Published Version
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