Multilayer route to iron nanoparticle formation in an insulating matrix

Abstract

Well-protected, isolated bcc-iron nanoparticles embedded in silicon dioxide were prepared by e-beam evaporation and postannealing of multilayers in an ultrahigh vacuum system. The spherical shape and isolation of the particles were confirmed by plan-view and cross-sectional transmission electron microscopy. Oxidation was evaluated from the electron energy-loss near edge structure. In this technique, a postedge peak of 40eV above the iron L3 threshold, originating from backscattering of oxygen atoms, provides a clear indication of iron oxide. The white-line ratio (WLR), measuring the 3d-orbital occupancy, is used to estimate the oxidation-layer thickness. In the samples of large iron nanoparticles (with average diameter larger than 10nm), a very thin surface layer appears to be the oxide maghemite, approximately one atomic layer according to the WLR evaluations. The evolution of the coercivity with particle size, as measured by the magneto-optical Kerr effect, shows that the reversal process is dominated by the surface anisotropy and is also affected by the dipole interaction, particularly in samples with large volume-filling factor.

Iron-containing nanomaterials: synthesis, properties, and environmental applications

“…The spherical shape and isolation of the particles were confirmed by plan-view and cross-sectional transmission electron microscopy. 106 Similarly, an approach using a lowenergy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. 107 Large-size 2D nano-TiO 2 and iron-doped nano-TiO 2 thin films were prepared 108 in a low-temperature aqueous system by using a molecular self-assembly method.…”

Synthetic Techniques and Applications of Activated Nanostructurized Metals: Highlights up to 2008

“…Thus, well-protected, isolated bcc-iron nanoparticles embedded in silicon dioxide were prepared by e-beam evaporation and postannealing of multilayers in an ultrahigh vacuum system. The spherical shape and isolation of the particles were confirmed by plan-view and cross-sectional transmission electron microscopy [155]. The formation of nanowires by electron beam writing in films of gold nanoparticles passivated with a specially designed class of ligand molecules (dialkyl sulfides) is presented, together with illustrations of practical nanostructures.…”

Efficient synthesis of iron nanoparticles by self‐agglomeration in a fluidized bed

“…Various physical and chemical methods have been developed to synthesize Fe NPs. Physical methods include high‐energy ball milling, vacuum evaporation, and pulsed plasma, but these methods are limited by the energy consumption required to maintain a high pressure and temperature. Two important routes of chemical synthesis are thermal decomposition and chemical reduction .…”