Epitaxial AlGaN/GaN layers grown by MBE on SiC substrates were irradiated with 150 MeV Ag ions at a fluence of 5×1012 ions/cm2. AlGaN/GaN MQWs were grown on Sapphire substrate by MOCVD and irradiated with 200 MeV Au8+ ions at a fluence of 5×1011 ions/cm2 . These samples were used to study the effects of SHI on optical properties of AlGaN/GaN based nano structures. RBS/Channelling strain measurements were carried out at off normal axis of irradiated and unirradiated samples. In as grown samples, AlGaN layer is partially relaxed with a small compressive strain. After irradiation this compressive strain increases by 0.22% in AlGaN layer. Incident ion energy dependence of dechannelling parameter shows E1/2 dependence, which corresponds to the dislocations. Defect densities were calculated from the E1/2 graph. As a result of irradiation defect density increased on both GaN and AlGaN layer. Optical properties of AlGaN/GaN MQWs before and after irradiation have been analyzed using PL. This study shows that SHI increase the confinement effects in the MQWs and intensity of the active layer of the MQWs luminescence is increased by one order. This may be due to the induced strain in GaN and AlGaN layers. Some unwanted yellow luminescence has also been introduced by the SHI possibly due the point defects or defect luminescence from the induced dislocations in GaN bulk epitaxial layers. In this study, we present some new results concerning high energy irradiation on AlGaN/GaN heterostructures and MQWs characterized by RBS/Channelling and PL.

High fluences of low energy Ge+ ions were implanted into Si matrix. We have also deposited Ge and SiO2 composite films by using the Atom beam sputtering (ABS). The as implanted/as-deposited films were irradiated by Swift Heavy Ions (SHI) with various energies and fluences. These pristine and irradiated samples were subsequently characterized by XRD and Raman to understand the crystallization behavior. Raman studies of the films indicate the formation of Ge crystallites as a result of SHI irradiation. Glancing angle X-ray diffraction results also confirm the presence of Ge crystallites in the irradiated samples. Moreover, the crystalline nature of Ge improves with an increase in fluence. Rutherford back scattering was used to quantify the concentration of Ge in SiO2 matrix and the film thickness. These detailed results have been discussed and compared with the ones available in literature. The basic mechanism for crystallization induced by SHI in these films will be presented.

The conducting carbon nanowires embedded in fullerene matrix are synthesized by high energy heavy ion irradiation of thin fullerene film. We report the control growth of carbon nanowires, their electrical and field emission properties. The typical diameter of the conducting tracks is observed to be about 40 to 100 nm. The conductivity of the conducting zone is about seven orders of magnitude higher than that of the fullerene matrix. Conducting atomic force microscopy evidences the conducting nano wires. All the nanowires are parallel to each other and are perpendicular to the substrate. The density (spacing), growth direction and length of these carbon nanowires simply can be changed by ion fluence, angle of irradiation and the film thickness, respectively. The field emission measurements on these nanowires reveal that the threshold voltage is about ( ~13 V/mm), whereas the as deposited fullerene films shows a break down at ( ~ 51 V/mm). The present approach of making controlled conducting carbon nanowires is quite promising, as it takes few seconds of ion irradiation and no catalyst is required.

Manganese-doped cadmium sulfide nanoparticles are synthesized in a flexible polymer matrix (synthetic rubber) by a chemical route. They are bombarded with 80-MeV oxygen ions having electronic energy loss (S e ) dominant over nuclear energy loss (S n ) and with fluence variation 1011–1013 ions/cm2. Piling up of nanoparticles along certain direction was observed in atomic force microscopy (AFM) images of irradiated samples. Such elongated nanostructures are as a result of nanoparticle growth during ion passage through the samples. Specifically, elongated structures in the form of nanoneedles, nanochannels and nanorods have been observed. The fluence dependent photoluminescence spectra (PL) show significant luminescent peaks at 445 nm and 706 nm, respectively which are tunable with ion fluence. Such a tunability could be promising as lasing materials in nano-luminescent devices and laser diodes. Further, detection of efficient third harmonic generation (THG) in these samples (by using irradiation of a Cr:fosterite laser) could be promising in nanoscopy and nonlinear optics.

Amorphous thin films of Se $_{80-x}$ Te20Pbx (0 < x < 2) have been prepared by thermal evaporation. The effect of 40 MeV 28Si5+ ion irradiation on the electronic conduction of Se $_{80-x}$ Te20Pbx (0 < x < 2) thin films has been investigated. The DC electrical conductivity of the films increases by two to three order of magnitude with increase in irradiation fluence from 1012 to 5×1013 ions/cm2. The DC activation energy of conduction also increases with increase in irradiation fluence. Results have been explained on the basis of structural disorders and defects formed due to heavy ion irradiation.

The present work reports phase transformations of thin films of C60 irradiated with 100 MeV 197Au8+ ions. This work is in continuation with our earlier work using 58Ni10+ and 16O6+ ions, to study the modification in C60 thin films. The study of C60 thin films using 197Au8+ ions, provides us enough additional data to investigate thoroughly the role of Se in causing phase transformations under different ion fluences. The Raman spectra indicate that swift heavy ion (SHI) irradiation results in several transformations of crystalline C60. At low fluences along with the fragmentation of C60 there is dimer/polymer formation. As fluence increases the dimer/polymer content first rises, optimizes, decreases and finally vanishes at very high fluences. At high fluences, all the C60 molecules as well as the polymer C60 break up, possibly resulting in nano-crystalline graphite embedded in amorphous carbon (a-C).