Role of electron energy loss in modification of C60 thin films by swift heavy ions

Abstract

This paper presents a comparative study of the effects of irradiation by swift heavy ions (SHIs) with Se values ranging from 80 to 1270 eV/Å and fluence ranges varying between 1010 and 1014 ions/cm2 incident on thin films of C60. The control over Se is exercised through the choice of ion species for irradiation (O, Ni, and Au). Structural changes in C60 were investigated quantitatively using Raman spectroscopy. The results indicate that at low fluences polymer formation takes place whereas at high fluences there is complete fragmentation of C60, resulting in amorphous carbon formation. Measured values of band gap and in situ resistivity decrease with fluence. This result is consistent with the structural modifications observed by Raman spectroscopy. The composition of the polymer fraction formed (e.g., the content of two dimensional polymerized network of C60 molecules) as well as that of a-C (e.g., the content of nanographite) also vary with Se of the ion used. A phenomenological model, taking into account the ion track, enables us to explain the trend of polymer formation as well as fragmentation of C60, with increasing fluence of SHI. The cross section for damage (fragmentation of C60 molecules) has two values—one effective at low fluences and the other at high fluences. By arriving at a quantitative formula giving the fraction of polymer/damaged C60 molecules at any given fluence, we are able to predict the fluence and ion species required for a given amount of polymerization/damage or vice versa. Effort has been made to correlate Se and Sn values to the damage cross sections using data from this work along with those from other experiments using keV and MeV ions.

Ubiquitous Organic Molecule-based Free-standing Nanowires with Ultra-high Aspect Ratios

“…Substituting the parameters of C 60 and C 70 into this equation, the G values of C 60 and C 70 are 35.1 and 15.3, respectively, indicating that the reaction e ciency of C 60 is about 2.3 times higher than that of C 70 . Dimerization reactions were reported both in C 60 and C 70 upon photo-exposure and irradiation to ionizing radiation (52)(53)(54). The estimated ~ 3-fold higher e ciency in solid C 60 than in C 70 (55) can well explain our experimental results for high-energy ion irradiation.…”

Modification of molecular transitions in fullerene films under ion impacts

“…It is known that the ion irradiation of fullerene thin films induces an ordering/polymerization at low fluence ͑Ͻ1 ϫ 10 13 ions/ cm 2 ͒ and a fragmentation of the molecules at higher fluence ͑Ͼ1 ϫ 10 13 ions/ cm 2 ͒. 6, [18][19][20] Earlier investigations on irradiated films showed an increase in oxygen content as a function of the ion fluence. 21,22 Therefore, the ion irradiation can be used to create discrete defects, a polymerization or a fragmentation, and oxidation of thin C 60 films by choosing the appropriate ion fluence, for tuning of the optical properties.…”

New Generation Fuel Cell Membrane Using Swift Heavy Ions

“…Similar behavior was observed in carbon nanostructures. The decrease in defects and improved crystallinity has been reported in the fullerene thin films,, CNT's and in graphene, under swift heavy ion irradiation at low fluence. Recently, the formation of nanostructures in the hollow region of surrounding ion track of polymer is demonstrated by Horio et al .…”