Size-selected fabrication of alloy nanoclusters by plasma-gas condensation

This work reports on the production of alloy Ti-Cu nanoclusters by magnetron sputtering and plasma-gas condensation inside an ultra-high compatible system. Inert-gas was introduced inside a source chamber to generate plasma, sputter material from its target, and establish plasma-gas condensation. The nanocluster size and yield were controlled by adjusting the nanocluster source conditions: inert-gas flow rate f_Ar, aggregation length L, and sputtering discharge power P. Nanoclusters were produced by three-body collision that created nanocluster embryo, and grew further by two-body collision. The dependence of nanocluster size on nanocluster source conditions was modeled using a homogeneous nucleation model where a nanocluster grows from embryo by nanocluster-nanocluster collision and vapor condensation. Controlled oxidation of ionized nanocluster was conducted in-situ which was found to affect nanocluster charge but retain its size. The nanoclusters were deposited on SiO₂/Si substrates with pre-formed metal electrodes to produce percolating nanocluster devices. Those devices have useful applications in many fields such as photoelectrochemical diodes for production of hydrogen fuel.