High pressure DC-magnetron sputtering on liquids: A new process for the production of metal nanosuspensions

Abstract

Vacuum evaporation on running liquids (VERL) is an established method for the production of metal nanoparticles in low vapor pressure carrier liquids like silicone oils or resins. Such metal suspensions may be useful, e.g. as additives for functional metal/polymer composites or for sintering additives in thick film pastes for microelectronics. In this paper we present a modified VERL-process employing high gas pressure dc magnetron sputtering for the preparation of suspensions of metal nanoparticles in various carrier liquids. By using magnetron sputtering, materials having high melting points can be evaporated without harming the liquid substrate. The method was tested for Ag and Fe-suspensions by varying the carrier liquid and the pressure of the Argon sputtering atmosphere in the range of 1–30 Pa. A narrow particle size distribution is obtained with the mean particle size 〈d〉 ranging from 2 to 20 nm. For Ag 〈d〉 increases with increasing gas pressure following roughly a power law type p ^1/3. The variation of particle size with sputtering gas pressure is consistent with in a model where particle formation takes place in the gas phase exclusively before introduction into the carrier liquid. In the case of Fe agglomeration could be prevented effectively by adding two different surfactants to the carrier liquid before starting the sputtering process.