Conducting nanowires parallel to each other, embedded in fullerene matrix are synthesized by high energy heavy ion irradiation of thin fullerene film at low fluence (up to 5×1011ions∕cm2). The conductivity of the conducting zone is about seven orders of magnitude higher than that of the fullerene matrix. The conducting nanowires are evidenced by conducting atomic force microscopy. The typical diameter of the conducting tracks is observed to be about 40–100nm. The creation of conducting wires is explained by transformation of fullerene to conducting form of carbon in the ion track, surrounded by the polymerized zone. The polymerization of fullerene is evidenced by Fourier transform infrared spectroscopy.
Thin silica films containing Au nanoparticles were prepared by cosputtering. The kinetics of the growth of nanoparticles under 90 MeV Ni ion irradiation was studied by in situ x-ray diffraction. The growth of nanoparticles from 4 (for pristine) to 9 nm at a fluence of 1×1014 ions/cm2 was observed, in accordance with the observations made by transmission electron microscopy analyses. The present study shows that the ion irradiation is an effective tool for tailoring the size of nanoparticles. The results are discussed in the framework of thermal spike model
Modification induced by 110 MeV Ni ion irradiated thin film samples of C 60 on Si and quartz substrates were studied at various fluences. The pristine and irradiated samples were investigated using Raman spectroscopy, electrical conductivity and optical absorption spectroscopy. The Raman data and band gap measurements indicate that swift ions at low fluences result in formations that involve multiple molecular units like dimer or polymer. High fluence irradiation resulted in sub-molecular formations and amorphous semiconducting carbon, indicating overall damage of the fullerene molecules. These sub-molecular units have been identified with nanocrystalline diamond and nanocrystalline graphite like formations. INTRODUCTIONEver since its synthesization in the laboratory 1 , the fullerene solid has been a subject of significant interest as target for ion-beam irradiation. The interest was stimulated by the potential of fullerene material towards superconductivity by implanting foreign ions in the fullerene cage and other applications like optical limiters, electrical storage devices, C 60 based diodes and transistors etc. Irradiation effects of keV and some MeV energies has been investigated [2][3][4][5][6][7][8][9][10][11][12][13][14] . In general, it has been observed by various research groups that the C 60 materials undergo heavy damage by low energy ion irradiation in the energy range 30 -300 keV of various ions [2][3][4][5][6] . There has also been study on irradiation effects of MeV energies on fullerene films [7][8][9][12][13][14] . Itoh et al 7 have reported fragmentation of C 60 induced by impacts of 2 MeV Si 4+ ions. T.Le.Brun et al 8 have reported ionization and fragmentation in C 60 molecules by impacts of Xe ions in the energy range of 420 -625 MeV. Subsequently 9 , there has been some interest in studying the phase transformations of the C 60 solids using MeV energies. It has been reported that under suitable conditions of temperature and pressure, the C 60 undergoes a dimer or a polymeric phase transformation 10,11 . Ion beam irradiation could provide similar conditions so that the formation of aggregates (of molecules of C 60 ) is favoured. This could further result in the formation of solids of these aggregates. The energy of the ions and their fluence play a key role in the end product of the target.Energetic ions loose energy during their passage in a material. The strength of interaction of the incident ion in a material i.e., with the electrons of the atoms in the target material (including the core electrons of the constituent atoms or molecules) as well as with the nuclei 2 (which happen to be the mass centers) depends on the mass, charge and energy of the incident ion. Therefore, it is of interest to study the interaction of ion beams with fullerene solids using swift ions at various fluences. The interaction of the incident ion with the atomic radii (or molecular mass center) is an elastic collision process and is prominent at low energy (eV to few hundred keV). On the other hand the intera...
Magnetic measurements using a superconducting quantum interference device and magnetic force microscopy were performed on fullerene films irradiated with 250 keV Ar and 92 MeV Si ions, to compare the effects of electronic excitation and collisional cascade on the magnetization. A ferromagnetic behavior increasing with ion fluence is observed. The magnetization is attributed to (i) the formation of an amorphous carbon network and (ii) the incorporation of oxygen in the irradiated films
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