Surface and structural studies of fullerene C70under ion irradiation

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.