Structural And Optical Study Of MeV Cobalt Ion Implanted Silicon

¹Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, Odisha India

²Department of Materials Engineering, Indian Institute of Science, Bangalore, India

³Condensed Matter Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India

⁴School of Physical Sciences, National Institute of Education and Research, Bhubaneswar 751005, Odisha, India

Adv. Mater. Lett., 2014, 5 (12), pp 699-705

DOI: 10.5185/amlett.2014.nib503

Publication Date (Web): Dec 02, 2014

Copyright © IAAM-VBRI Press

E-mail: pramitam@iopb.res.in

Abstract

We report the optical tunability through defect states created in silicon by 1 MeV cobalt ion implantation at room temperature in the fluence range of 5 × 10¹³ to 5 × 10¹⁵ ions cm^-2. Atomic force microscopy studies reveal the surface nanostructures with maximum roughness of 0.9 nm at a critical fluence of 5 × 10¹⁵ ions cm-2 which is reduced to 0.148 nm with further increase of fluence. The enhanced native oxide layers after Co ion implantation observed from X-Ray photoelectron spectroscopy studies confirm the presence of surface defects. The combined effect of nanostructures formation and amorphization leads to band gap tailoring. For low fluence, the nanostructures produced on the surface result in an enhanced absorption in the entire UV-Visible region with a simultaneous reduction in band gap of 0.2 eV in comparison to pristine Si whereas high fluence implantation results in interference fringes which signifies the enhancement in refractive index of the top implanted layer ensuing increase in band gap of 0.3 eV. Combined amorphous and crystalline phases of nanostructured surface with tunable optical absorption may have potential applications in solar cell, photovoltaics and optical sensors.

Keywords

Nanostructures, amorphization, Raman spectroscopy, XPS absorbance