Spontaneous organization of columnar nanoparticles in Fe-BN nanocomposite films

Ion-beam sputtering codeposition assisted with either reactive (nitrogen) or inert gas (neon, argon, and krypton) has been used to fabricate Fe-BN nanocomposite thin films of Fe-rich nanoparticles encapsulated in nanocrystalline boron nitride. A combination of high-resolution and conventional transmission electron microscopy (TEM), grazing incidence small-angle x-ray scattering (GISAXS), electron diffraction, x-ray absorption, and Moessbauer spectroscopy has been used to investigate the structural characteristics of these films, both at nanometric and atomic scales. Crystallized {epsilon}-Fe{sub 3}N nanoparticles (typically 2.5 nm in size) have been obtained in N assisted films, whereas self-organized arrays of amorphous Fe{sub 2}B nanocolumns ({approx}3 nm in diameter and {approx}10 nm in height, with small size dispersion) have been synthesized in inert-gas assisted films. Quantitative analysis of the GISAXS patterns and of the local autocorrelation functions of the TEM images indicate a better spatial ordering in the 50 eV Ar assisted films, i.e., when backscattering and sputtering effects are minimized. Our results shows that low-energy assistance with light ions can be used to control the morphology as well as the spatial ordering and chemical composition of nanoparticles in insulating matrix.