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The topography evolution using the high energy heavy ion irradiation revealed the fact that ion bombardment produces self-affine nanostructures, creating peculiar surface morphologies and regular structures on the surface of the ZnO thin film at certain fluences. The self-affine nanopatterns produced on the surface of ZnO thin film under swift heavy ion irradiation are different types of nanostructures such as nanodimensional grains aligned like a linear array. Scanning probe microscopy is used for investigating the ZnO surfaces and UV-visible spectroscopy for studying the effect of surface modification on optical properties. The two-dimensional power spectral density of the irradiated ZnO thin films have been evaluated for each image to extract the value of growth factor (β) and roughness exponent (α). The exponent n increases from 2.2 to 4.0 up to a critical value of fluence and beyond which it decreases. These values suggest that ion assisted/induced diffusion process plays a crucial role in the evolution of self-affine nanostructures on ZnO surface. [ABSTRACT FROM AUTHOR]

High energy light ions have been used to engineer the electrical properties of semi-insulating InP and GaAs by creation and annihilation of native defects. Due to light mass, high energy ions lose most of their energy during flight inside the material by electronic excitation, which also modifies the charge states of the defect. Imbalance in charge compensation caused by irradiation induced defect engineering results in the modification of resistivity of the semi-insulating samples. The activation energies of the defect levels responsible for the modified resistivity have been estimated from the measurement of thermally activated currents. It is shown that the modified charge compensation is due to annihilation and/or creation of native defects depending on the material (GaAs or InP) and the fluence of irradiated ions. It has also been observed that annealing does not have any effect on modified compensation in InP, but in the case of GaAs, compensation recovers after thermal annealing. [ABSTRACT FROM AUTHOR]

The reactivity of the Zr/Si interface induced by swift heavy ion beams of Au has been investigated in the present work. Zirconium was evaporated on a clean silicon substrate in ultra high vacuum (UHV) at a pressure of 10-8 Torr by the electron beam evaporation technique and the final layer was a thin film of Au to avoid oxidation of zirconium. The Zr/Si system was irradiated by 350 MeV Au26+ ions at liquid nitrogen temperature at different fluences (0.46×1014, 1.85×1014 and 4.62×1014 ions/cm2). Rutherford back scattering (RBS) spectroscopy using 2 MeV He ions was used to monitor the Zr and Si concentration profiles and interdiffusion at the interfaces. The irradiation at the Zr/Si interface showed mixing. X-ray diffraction measurements confirmed the formation of the ZrSi2 phase. Thermal spike formation and melting in the tracks was found to be the dominant process at the interfaces. [ABSTRACT FROM AUTHOR]

Swift heavy ions of Au at 120 MeV are irradiated at the interface of Si/Me/Si (Me=V,Fe,Co) and the behaviour of mixing examined wrt to different ion doses. The fluences were varied from 1x1013 ions/cm² to 1x1014 ions/cm² on the multilayers of Si/Me/Se (Me=V,Fe,Co) and the interface of Si/Me(Me=V,Fe,Co) were characterised using Rutherford backscattering spectroscopy(RBS) and secondary ion mass spectrometry (SIMS). The atomic mixing width was found to be increasing monotonically with ion fluence in all the three cases,. The mixing rate and efficiency calculations were made and the diffusivity values thus obtained suggested a transient melt phase at the interface according to thermal spike model. In case of Me=Co, it was further probed with XRD and Raman spectroscopy to confirm the formation of cobalt silicides even at room temperature. [ABSTRACT FROM AUTHOR]

Polycrystalline CdTe thin films were irradiated with 80 MeV oxygen (O6+) ions for various fluences and its effect on the composition, structure, surface topography and optical properties have been investigated. The as-grown films are found to be slightly Te-rich in composition and there is no significant change in the composition after irradiation. X-ray diffraction analysis shows a high degree of crystallite orientation along the (111) plane of cubic phase CdTe. Upon irradiation a large decrease in intensity of the (111) plane and a small shift in the peak position has been resulted. The shift in the peak position is correlated with the change in the residual stress. The surface roughness of the films get increased after irradiation. A decrease in the grain size was observed after irradiation due to ion-induced recrystallization. The optical band gap energy decreased from 1.53 eV for as-grown film to 1.46 eV upon irradiation. The photoluminescence (PL) spectrum is dominated by the defect band and the effect of irradiation has been discussed and correlated with the observed change in the XRD peak position and optical band gap. [ABSTRACT FROM AUTHOR]

Gold nanoparticles embedded in silica matrix were prepared by co-evaporation. After deposition, the samples were annealed at different temperatures in inert environment for 30 min. No signature of nanoparticle formation was found in case of as-deposited samples, while the annealed samples showed a clear signature of a surface plasmon resonance absorption peak around 520 nm, which indicated the formation of Au nanoparticles. The samples annealed at 900 °C were irradiated with 100 MeV Ag ions at fluences 2.5×1012 and 1×1013 ions/cm2. UV-visible absorption measurements of pristine and irradiated films showed a clear signature of dissolution of Au nanoparticles with ion beam fluence. X-ray diffraction studies of pristine and irradiated samples also supported the dissolution of Au nanoparticles with ion beam fluence. Rutherford backscattering spectrometry was used for quantification of gold. [ABSTRACT FROM AUTHOR]

Abstract: The irradiation effect of 350MeV Au+ ions on Ti/Si multilayers has been studied using Rutherford backscattering spectroscopy, X-ray reflectivity (XRR) and grazing incidence X-ray diffraction (GIXRD). Intermixing effects have been studied as a function of fluences of 0.46×1014, 1.82×1014 and 4.62×1014 cm−2. Rutherford backscattering spectra (RBS) confirm mixing at the interface. X-ray reflectivity patterns show damage at the interfaces with the absence of a continuous fringe pattern at high fluence doses in comparison to the pristine interface. Mixing leads to titanium di-silicide (TiSi2) phase formation as a shown by grazing incidence X-ray diffraction patterns. The observed intermixing is attributed to energy deposited by the incident ions in the electronic system of the target. Swift heavy ion irradiation induced intermixing increases with fluence. [Copyright &y& Elsevier]

Abstract: Formation of Ge crystallites in GeOx matrix as a result of heavy ion irradiation is reported. Micro-Raman spectra of the films show the evolution of Ge crystallite regions in GeOx thin films upon ion irradiation with 100 MeV Au. Transmission electron microscopic studies of the irradiated films revealed the presence of Ge crystallites. Crystallinity of the Ge nanoparticles was confirmed by high-resolution electron microscope images. Atomic force microscopy was employed to study the modifications in surface morphology of GeOx films before and after irradiation. Formation of Ge nanocrystallites has been explained on the basis of phenomenon of ion beam induced phase separation. [Copyright &y& Elsevier]

Isotopically enriched targets of 64,68Zn were prepared for heavy ion fusion and multi-nucleon transfer reactions. In view of the fragility of the targets under the ion current and during characterization, multiple targets of each isotope were required. Thin films of 64,68Zn isotopes were fabricated via vapor deposition in the target laboratory at Inter-University Accelerator Center (IUAC), New Delhi. Multiple targets of 64,68Zn in the thickness range 150 μ g/cm2–300 μ g/cm2, were synthesized on a carbon backing of 10 μ g/cm2 using only 30 mg amount of available enriched material for each isotope. The use of a pin source and carbon foils as substrate allowed the fabrication of Zn targets without employing previously suggested methods of substrate cooling and forced condensation for thin film fabrication of volatile elements. The deposition results have been estimated quantitatively. The thickness measurement of the targets was carried out using the α particle energy loss technique and Rutherford Back Scattering (RBS) method. The elemental composition of the targets was examined using RBS and Dispersive Wavelength X-ray Fluorescence (DWXRF) to investigate the contamination. Morphological analysis of the films was performed using Scanning Electron Microscope (SEM) to study homogeneity and the impact of ion bombardment on the targets. • Thin film fabrication of Zn is difficult due to its low vapor pressure. • Use of a pin source provides needful vapor pressure for condensation of Zn vapors. • Use of carbon foils as substrate provides consistent deposition of Zn vapors. • Effect of ion irradiation on thin film is highlighted. [ABSTRACT FROM AUTHOR]

Importance of substrate heating for fabrication of strong zirconium targets ( 92 Zr) has been discussed. The targets have been prepared using experimental facilities of target laboratory at Inter University Accelerator Centre (IUAC), New Delhi, India. Substrate heating has been tried for the first time for the fabrication of carbon backed zirconium targets. The heating of substrate exhibited improved stability, longevity and a better success rate of production of targets. In addition, a large number of wrinkle-free targets have been obtained using this technique. Elemental analysis has been performed to determine purity of the targets with X-ray fluorescence and Rutherford back-scattering spectrometry methods. These targets have successfully survived against high flux heavy ion bombardment viz. 14 N and 28 Si. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, we have studied the nano/micro-patterning of the surface of NiO thin films on different substrates (SiO2, Si and Al) using 100 MeV Ag ions at LN2 temperature and at an incidence angle of 75° with the beam axis. The surface morphology of the irradiated surface is observed by Atomic force microscopy (AFM). AFM images of ion beam irradiated samples show the restructuring of initially flat and coherent NiO film into an almost periodic NiO lamellae structure. The quite regular lamellae with width, height and average distance of hundreds of nm are oriented perpendicular to the beam direction. Section analysis of the AFM images reveal that the width of the lamellae is less in case of NiO films deposited on SiO2 substrate in comparison to Al substrate. The cracking and the development of lamellae structure is observed at higher fluence in the case of Al substrate in comparison to other substrates. [Copyright &y& Elsevier]

Abstract: Ion beam mixing has emerged as a technique for understanding reactivity and chemistry at metal/Si interface and may find its applications in the field of microelectronics. We have investigated ion beam mixing at Co/Si interface induced by electronic excitation using 120MeV Au+9 ion irradiation at different fluences, varying from 1012 to 1014 ions/cm2. Mixing was investigated by Rutherford Backscattering Spectroscopy (RBS) as a function of ion fluence and its mechanism across the interface is explained by the thermal spike model. [Copyright &y& Elsevier]

Abstract: The effect of 100MeV Ag+7 ion irradiation on the properties of thermally evaporated CdS thin films has been investigated. The structure of the films studied is polycrystalline with a mixture of dominant hexagonal and few traces of cubic phases. A shift in the peak position due to irradiation was observed and is discussed on the basis of change in the residual stress. Annihilation of microcracks due to irradiation induced grain growth has been observed from the SEM micrographs at lower ion fluences. The optical transmittance and absorption spectra revealed a shift in the fundamental absorption edge and hence variations in the optical band gap. The band gap energy has been estimated for as-deposited and irradiated films and is found to decreases upon irradiation. A significant increase of refractive index has been observed after irradiation. [Copyright &y& Elsevier]

Abstract: We have investigated the influence of swift heavy ion (SHI) irradiation as well as thermal annealing on the interface roughness in thermally immiscible Fe/Au and Fe/Ag multilayers. The 5-fold multilayers consisted of 20–25nm Fe-, 10nm Ag- and 7–21nm Au-layers and were partly irradiated at liquid nitrogen temperature with 80–350MeV Ar, Ni, Kr, Xe ions at fluences between 1012 cm−2 and 1015 cm−2. The irradiated as well as the unirradiated parts of the samples were analyzed by means of Rutherford backscattering spectrometry (RBS) using 1MeV He+ ions. In the case of Fe/Ag, no change in the RBS spectra due to the ion irradiation could be detected, while in the case of Fe/Au, a clear increase of the steepness of the high energy edge of the Au signal was observed. A detailed analysis of the RBS Au profiles in comparison with RBS simulations for different shapes of the Au-layers allowed us to conclude that SHI irradiation results in smoothing of the Fe–Au interfaces, which can be understood in terms of a local minimization of the interface energy. In the Fe/Ag case, the symmetry of the RBS profiles of the Ag layers indicated that the interfaces became already smooth during the layer deposition. Heating of the Fe/Au multilayers resulted in broadening of the Au profiles and finally a complete destruction of the multilayer structure was observed. Here the whole sample is at high temperature and therefore interface energy minimization now occurs by the formation of spherical Au particles, which destroys the layered structure. [Copyright &y& Elsevier]

Abstract: Based on the potential need of making nano-dimensional contact materials for successful miniaturization of nanoscale devices, we have attempted to synthesize nano-dimensional alloys on the surface of a material. This method has been termed as nanomixing. In this paper, we report on formation of nano-dimensional Au–Ge alloy islands by ion beam mixing of island thin films of Au and Ge. The nanoislands of Au and Ge were grown by UHV electron beam evaporation technique on Si(100) surface covered with a thin native oxide layer and were irradiated later on by different energetic ions (viz. 1.5MeV Au, 800keV Ar and 800keV Xe) at room temperature over a fluence range of 1×1014–2×1016 ionscm−2. We have carried out high-resolution transmission electron microscopic study to confirm the formation of Au–Ge alloy in the form of nanoislands. [Copyright &y& Elsevier]

Abstract: Tailoring of nanostructures with energetic ion beams has become an active area of research leading to the fundamental understanding of ion–solid interactions at nanoscale regime and with possible applications in the near future. Rutherford backscattering spectrometry (RBS), high resolution transmission electron microscopy (HRTEM) and asymmetric X-ray Bragg-rocking curve experimental methods have been used to characterize ion-induced effects in nanostructures. The possibility of surface and sub-surface/interface alloying at nano-scale regime, ion-beam induced embedding, crater formation, sputtering yield variations for systems with isolated nanoislands, semi-continuous and continuous films of noble metals (Au, Ag) deposited on single crystalline silicon will be reviewed. MeV-ion induced changes in specified Au-nanoislands on silicon substrate are tracked as a function of ion fluence using ex situ TEM. Strain induced in the bulk silicon substrate surface due to 1.5MeV Au2+ and C2+ ion beam irradiation is determined by using HRTEM and asymmetric Bragg X-ray rocking curve methods. Preliminary results on 1.5MeV Au2+ ion-induced effects in nanoislands of Co deposited on silicon substrate will be discussed. [Copyright &y& Elsevier]

In the present work, we report the formation of silicide phases in the Au/Si system by ion beam mixing at room temperature. The samples (58 nm Au on Si) were irradiated by 1 MeV Xe ions. The ion energy was chosen in such a way that it deposits maximum energy at the interface. The Rutherford backscattering spectrometry measurements were done on the pristine and irradiated samples to determine the composition of mixed region. Grazing incidence X-ray diffraction measurements were performed which showed the formation of silicide phase (Au2Si, Au3Si, Au5Si and Au5Si2). Scanning electron microscopy measurements indicated the micron size crystallites in the irradiated samples. [Copyright &y& Elsevier]

An optical study of GaAs 〈1 0 0〉, undoped, irradiated with 50 MeV Li-ion at room temperature with a fluence ranging from 1×1011 to 1×1014 ions/cm2 using Pelletron ion beam facility of Nuclear Science Centre (NSC), New Delhi has been carried out in the spectral regions of the fundamental optical absorption and interband transition. The damage induced by the MeV ion in the surface and deep inside the semiconductor has been monitored by determining the ion fluence dependence of the optical constants: absorption coefficient (α), reflection (R), ion-irradiation induced defect density (Ns) and optical energy gap (Eg) in the spectral range 200–2500 nm. The present study reveals that the ion irradiation does not induce significant changes in the surface of a semiconductor. The fundamental optical absorption spectra are, however, greatly modified by MeV energy ion–solid interaction. [Copyright &y& Elsevier]

Abstract: Formation of regular nanostructures of zinc oxide (ZnO) by bombardment of 15keV Ar+ ions on 400nm thick ZnO film deposited on Si〈100〉 is accomplished. Roughness of the bombarded films was reduced and bigger structures disintegrated into smaller ones. This reduction in roughness and grain size has been attributed to the elastic collisions induced rearrangement of surface atoms along with sputtering from the surface. [Copyright &y& Elsevier]