= Solution
In <cluster-beam deposition>, evaporated or sputtered cobalt atoms cool in an aggregation gas, nucleate clusters and are carried to a substrate. Source <temperature>, gas pressure, aggregation length and residence time tune the mean size and distribution. A <mass> selector can narrow the delivered size range, at the cost of transmitted flux; an unfiltered beam does not automatically produce monodisperse particles.
Shape control is less direct. Growth kinetics and cluster <temperature> can favour particular structures, while multiple morphologies can coexist at one size. Landing <energy>, substrate interactions and post-deposition annealing can change the delivered shape or cause coalescence. Soft landing helps preserve gas-phase clusters. In solution, <ligands>, selective facet binding, seed-mediated growth and precursor feeding can give stronger chemical control over shape and size, but introduce <ligand>/solvent residues and require purification. \b[Neither method guarantees a unique shape merely by selecting particle size.]
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