The effect of oxidation on the structure of nickel nanoparticles

The structural properties of nickel nanoparticles which are prepared by mea ns of DC sputtering in argon and subsequently oxidized in ambient air are r eported. Ex situ structural and chemical investigations utilizing (high res olution) transmission electron microscopy and electron energy loss spectros copy reveal that the particles consist of a metallic core surrounded by an oxide shell. The lattice constant of the nickel core is found to increase s ignificantly with decreasing particle size. This widening of the nickel lat tice is attributed to an interfacial stress that originates from the lattic e mismatch between nickel and nickel oxide.