Nano tracks in fullerene film by dense electronic excitations

In the present work, we investigate the formation of nano tracks by cluster and mono-atomic ion beams in the fullerene (C60) thin films by High Resolution Transmission Electron Microscopy (HRTEM). The fullerene films on carbon coated grids were irradiated by 30 MeV C60 cluster beam and 120 MeV Au mono-atomic beams at normal and grazing angle to the incident ion beams. The studies show that the cluster beam creates latent tracks of an average diameter of around 20 nm. The formation of large size nano tracks by cluster beam is attributed to the deposition of large electronic energy density as compared to mono-atomic beams.Comment: Under revision. Applied Surface Science (2014

Shape deformation of embedded metal nanoparticles by swift heavy ion irradiation

an invited paper of SHIM 2008Swift heavy ions (SHI) induce high densities of electronic excitations in narrow cylindrical volumes around their path. These excitations have been used to manipulate the size and shape of noble metal nanoparticles embedded in silica matrix. Films containing noble metal nanoparticles were prepared by magnetron co-sputtering techniques. SHI irradiation of films resulted in the formation of prolate Ag nanoparticles with major axis along the ion beam direction. It has been observed that the nanoparticles smaller than the track size dissolve and other grow at their expense, while the nanoparticles larger than track size show deformation with major axis along the ion beam direction. The aspect ratio of elongated nanoparticles is found to be the function of electronic energy loss and ion fluence. Present report will focus on the role of size and volume fraction on the shape deformation of noble metal nanoparticles by electronic excitation induced by SHI irradiation. The detailed results concerning irradiation effects in silica-metal composites for dissolution, growth and shape deformation will be discussed in the framework of thermal spike model

Dielectric response of makrofol-KG polycarbonate irradiated with 145 MeV Ne6+ and 100 MeV Si8+ ions

The passage of heavy ions in a track detector polymeric material produces lattice deformations. These deformations may be in the form of latent tracks or may vanish by self annealing in time. Heavy ion irradiation produces modifications in polymers in their relevant electrical, chemical and optical properties in the form of rearrangement of bonding, cross-linking, chain scission, formation of carbon rich clusters and changes in dielectric properties etc. Modification depends on the ion, its energy and fluence and the polymeric material. In the present work, a study of the dielectric response of pristine and heavy ion irradiated Makrofol-KG polycarbonate is carried out. 40 μm thick Makrofol-KG polycarbonate films were irradiated to various fluences with Si8+ ions of 100 MeV energy from Pelletron at Inter University Accelerator Centre (IUAC), New Delhi and Ne6+ ions of 145 MeV from Variable Energy Cyclotron Centre, Kolkata. On irradiation with heavy ions dielectric constant ( ) decreases with frequency where increases with fluence for both the ions. Variation of loss factor (tan ) with frequency for pristine and irradiated with Si ions reveals that tan increases as the frequency increases. Tan also increases with fluence. While Ne irradiated samples tan shows slight variation with frequency as well as with fluence. Tan has positive values indicating the dominance of inductive behavior.Author Affiliation: Rajesh Kumar, S Asad Ali, Udayan De, D K Avasthi and Rajendra Prasad 1.Department of Applied Physics, Z H College of Engineering & Technology, Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh, India 2.Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata-700 064, India 3.Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110 067, India E-mail : [email protected] of Applied Physics, Z H College of Engineering & Technology, Aligarh Muslim University, Aligarh-202 002, Uttar Pradesh, India Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata-700 064, India Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi-110 067, Indi

Modification and Characterisation of Materials by Swift Heavy Ions

Swift heavy ions (SHI) available with 15 million Volt Pelletron accelerator at Inter University Accelerator Centre (IUAC) Delhi, formerly known as Nuclear Science Centre, (NSC), provide a unique opportunity to researchers for accelerator based materials science research. The major research areas can be broadly categorised as electronic sputtering, interface modifications, synthesis and modification of nanostructures, phase transitions and ion beam-induced epitaxial crystallisation. In, general, SHI irradiation based-materials may not be economically feasible, still it could be of interest for very specific cases in defence and space research. The paper gives a glimpse of the current research activities in materials science with SHIs, at IUAC.Defence Science Journal, 2009, 59(4), pp.401-412, DOI:http://dx.doi.org/10.14429/dsj.59.154