Abstract
This article reviews the size-dependent structural properties of ion beam synthesized Co nanoparticles (NPs) and the influence of ion irradiation on the size, shape, phase and structure. The evolution of the aforementioned properties were determined using complementary laboratory- and advanced synchrotron-based techniques, including cross-sectional transmission electron microscopy, small-angle X-ray scattering and X-ray absorption spectroscopy. Combining such techniques reveals a rich array of transformations particular to Co NPs. This methodology highlights the effectiveness of ion implantation and ion irradiation procedures as a means of fine tuning NP properties to best suit specific technological applications. Furthermore, our results facilitate a better understanding and aid in identifying the underlying physics particular to this potentially technologically important class of nanomaterials.
Highlights
In recent years the advantageous optical, electrical and magnetic properties of nanoparticle-based materials have made them the focus of an intensive research effort in a range of scientific disciplines.In particular, the drive for further miniaturization of electronic, magnetic and photonic devices has led to numerous experimental and theoretical efforts to understand the physical properties of various metal and semiconductor nanoparticles (NPs) with emphasis on the effects of size, shape and host matrix
We only focus on samples that have been annealed after implantation, since the as-implanted samples have a considerable fraction of Co atoms in an oxidised state
The fraction of oxidised Co atoms were progressively converted to the metallic hexagonal closed packed (HCP) and face-centered cubic (FCC) phases with an increase in temperature
Summary
In recent years the advantageous optical, electrical and magnetic properties of nanoparticle-based materials have made them the focus of an intensive research effort in a range of scientific disciplines.In particular, the drive for further miniaturization of electronic, magnetic and photonic devices has led to numerous experimental and theoretical efforts to understand the physical properties of various metal and semiconductor nanoparticles (NPs) with emphasis on the effects of size, shape and host matrix The size-dependent structural, and vibrational properties of metallic NPs differ considerably compared to those of their bulk counterparts. Such differences stem from a large fraction of surface atoms compared to the NP volume, or large surface-to-bulk ratio (SBR). We discuss the effect of low energy ion irradiation on the size and atomic structure of Co NPs. The amorphisation of small Co NPs was readily apparent with low fluence irradiation. We have performed MD simulations of the atomic structure for bulk amorphous Co for comparison with experimental results and have investigated the vibrational properties of amorphous Co NPs using temperature-dependent XAS measurements. Samples were subsequently irradiated at room temperature with 197 Au ions at 27, 89 or 185 MeV over a wide fluence range of 1012 –1014 /cm at normal incidence
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