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Synthesis of cobalt nanoparticles on Si (100) by swift heavy ion irradiation

Asha Attri1, Ajit Kumar1, Shammi Verma2, Sunil Ojha2, Kandasami Asokan2 and Lekha Nair1*

Author Affiliations

1 Department of Physics, Jamia Millia Islamia, New Delhi 110025, India

2 Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 India

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Nanoscale Research Letters 2013, 8:433  doi:10.1186/1556-276X-8-433

Published: 18 October 2013

Abstract

We report the growth and characterization of uniform-sized nanoparticles of cobalt on n-type silicon (100) substrates by swift heavy ion (SHI) irradiation. The Co thin films of 25-nm thicknesses were grown by e-beam evaporation and irradiated with two different types of ions, 45-MeV Li3+ and 100-MeV O7+ ions with fluences ranging from 1 × 1011 to 1 × 1013 ions/cm2. SHI irradiation, with the beam rastered over the area of the film, resulted in the restructuring of the film into a dense array of Co nanostructures. Surface topography studied by atomic force microscopy revealed narrowed size distributions, with particle sizes ranging from 20 to 50 nm, formed through a self-organized process. Ion fluence-dependent changes in crystallinity of the Co nanostructures were determined by glancing angle X-ray diffraction. Rutherford backscattering spectroscopy analysis showed the absence of beam-induced mixing in this system. Surface restructuring and beam-induced crystallization are the dominant effects, with the nanoparticle size and density being dependent on the ion fluence. Results are analyzed in the context of molecular dynamics calculations of electron-lattice energy transfer.

Keywords:
Cobalt nanostructures; Ion irradiation; Surface restructuring; Atomic force microscopy; Thin films