Structural study of self-assembled Co nanoparticles

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Abstract
We studied the ordering of colloidal Co nanoparticles on various types of substrates by grazing-incidence small-angle x-ray scattering, transmission electron microscopy, and scanning electron microscopy. Particles of 5–6 nm radius were deposited by spin coating in order to obtain uniform distribution of the particles over a large surface area. Only by the grazing-incidence small angle x-ray scattering technique could the distribution of particles on a large surface area be analyzed in detail. For quantitative analysis of the spectra the distorted-wave Born approximation approach was applied. From simulations of the spectra the particle radius, the spherical shape, the mean spacing between the particles, and the type of ordering were determined. The distribution of the particles on the surface can be described by a hexagonal close-packed structure with local order. This corresponds to the transmission electron microscopy data obtained for the same type of substrate. The parameters that affect the ordering of Co nanoparticles are discussed.