The nanocluster source is used to deposit size-selected nanoclusters. It is situated within the group’s primary sputtering system, allowing the nanoclusters to be deposited within multilayer thin-film structures.
The nanocluster source uses the gas condensation method. Atoms are generated from a DC magnetron sputter source, and then pass into a gas aggregation region. Within this region, which is filled with a small partial pressure of cooled inert gas, the sputtered products condense into clusters and then pass through a small aperture into the quadrupole filter where the ions are mass selected. Finally, steering plates are used to direct the ions into the deposition chamber and onto the substrate, filtering out any neutral clusters.
The cluster size can be varied by controlling the flow of aggregation gas, the power to the magnetron and the size of the aggregation region, in addition to the quadrupole mass-selection. In Leeds, we use an Oxford Applied Research NC200U-B nanocluster source. The figure below is an AFM image of Co nanoclusters.