Surface and structural studies of fullerene C 70 under ion irradiation

Abstract

Thin films of C₇₀ were grown on double side polished silicon substrate by resistive heating of C₇₀ powder. These films were irradiated with 90 MeV Si⁷⁺ ions at different fluences in the range from 1 × 10¹² to 6 × 10¹³ ions cm⁻². The investigations on structural and surface modifications were made (after irradiation) by Raman spectroscopy and atomic force microscopy (AFM), respectively. Raman spectroscopic studies reveal that C₇₀ is not completely transformed into amorphous carbon at a fluence of 6 × 10¹³ ions cm⁻². Swift heavy ion irradiation generates nanometre size conducting tracks in fullerenes. For 90 MeV Si ions irradiated C₇₀ fullerene, the damage cross-section (σ) and radius of damaged cylindrical zone were estimated from Raman spectra, to be ∼0.32 × 10⁻¹³ cm² and ∼1.01 nm, respectively, using vibrational modes of C₇₀. From AFM study it is clear that the film irradiated at a fluence of 3 × 10¹² ions cm⁻² shows maximum roughness. Contact angle measurements have been performed to know about hydrophilic or hydrophobic nature of fullerene C₇₀ thin films.