Ni–NiO core-shell nanoclusters with cubic shape by nanocluster beam deposition

Ni nanoclusters with cubic shape and uniform size below 10nm were fabricated by nanocluster beam deposition. Ni–NiO core-shell structure was achieved when the Ni clusters flew through a chamber with constant oxygen feeding (1–3SCCM, SCCM denotes cubic centimeter per minute at STP). The fraction of oxidized Ni was estimated by means of linear combination fitting to the x-ray absorption near-edge structure data. The hysteresis loop of the oxidized sample (1SCCM O2) showed a shift of ∼181Oe with 100Oe field cooling from 400K and a coercivity of 48Oe at room temperature, while the nonoxidized Ni nanoclusters with size of 4–5nm showed superparamagnetic behavior.