V. Saikiran; N. Manikanthababu; N. Srinivasa Rao; S. V. S. Nageswara Rao; A. P. Pathak
Abstract
Trilayered HfO2/Ge/HfO2 thin films were grown on Si substrate by RF magnetron sputtering with HfO2 and Ge targets. The subsequent rapid thermal annealing (RTA) of these films at 700 & 800°C results in formation of Ge nanocrystals (NCs) in HfO2 matrix. X-ray diffraction (XRD) and micro-Raman spectroscopy ...
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Trilayered HfO2/Ge/HfO2 thin films were grown on Si substrate by RF magnetron sputtering with HfO2 and Ge targets. The subsequent rapid thermal annealing (RTA) of these films at 700 & 800°C results in formation of Ge nanocrystals (NCs) in HfO2 matrix. X-ray diffraction (XRD) and micro-Raman spectroscopy measurements were performed to confirm the formation of Ge NCs in the annealed samples. XRD results indicate that the as-deposited samples show amorphous behaviour, whereas the annealed samples clearly confirm the crystallinity of the films. The average size of the Ge NCs was found to increase with an increase in annealing temperature. Raman scattering studies confirm that the annealed samples exhibit a shift in peak position corresponding to Ge-Ge optical phonon vibrations, which clearly indicates the formation of Ge NCs. Conversely, as-deposited samples were also irradiated with swift heavy ions of 150 MeV Au and 80 MeV Ni at a fluence of 3×10 13 ions/cm 2 to synthesize Ge NCs. The structural properties of pristine and irradiated samples have been studied by using X-ray diffraction, Raman spectroscopy to substantiate the growth of Ge NCs upon irradiation. The results obtained by RTA are compared with the irradiated ones.
Priyadarshini Dash; Haripriya Rath; Udai B. Singh; Sunil Ojha; Devesh K. Avasthi; Naresh C. Mishra
Abstract
Two sets of gold thin films of thickness of about 20 and 50 nm, grown by thermal evaporation method on (100) silicon wafers were irradiated by 197 MeV Au ions. Grazing incidence X-Ray diffraction (GIXRD) study has been revealed lattice expansion on decreasing the film thickness. 197 MeV Au ion irradiation ...
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Two sets of gold thin films of thickness of about 20 and 50 nm, grown by thermal evaporation method on (100) silicon wafers were irradiated by 197 MeV Au ions. Grazing incidence X-Ray diffraction (GIXRD) study has been revealed lattice expansion on decreasing the film thickness. 197 MeV Au ion irradiation was not affect either the cubic crystal structure of gold or its lattice parameter. Atomic force microscopy (AFM) study indicated that the evolution of the surface morphology with ion fluence crucially depended on the film thickness, the thinner film being more sensitive than the thicker one. Irradiation led to nanoparticles formation on the surface of the films. This observation is in contrast to the generally perceived damaging role of swift heavy ion (SHI) irradiation. Power spectral density analysis of the roughness along both the lateral and vertical directions demonstrated dominance of surface diffusion over volume diffusion induced by SHI irradiation. A comparison of the sputtering yield obtained from Rutherford back scattering (RBS) spectra of the irradiated films and transmission electron microscopy (TEM) of the particles sputtered from the films and collected by a catcher grid during irradiation indicated that more than the surface and volume diffusion processes, it is the irradiation induced sputtering that controls the overall surface morphology of the films. The surface roughness increase with ion fluence and the irradiation induced sputtering yield was found to be larger in thinner films. Film thickness dependence of the evolution of surface morphology and sputtering yield with 197 MeV Au ion irradiation clearly indicates the dominance of the electronic energy loss over the nuclear energy loss of the projectiles ions in the target medium and opens up the ways for examining the applicability of different models of ion-matter interaction in systems with reduced dimensions.
P. Jegadeesan; S. Amirthapandian; Kitheri Joseph; C. David; B.K. Panigrahi; K.V. G Kutty
Abstract
Iron phosphate glass (IPG) is considered as a suitable matrix for the immobilization of nuclear waste containing higher concentration of Cs, rare earth, Mo and Cr. The central issue, while disposing nuclear waste in glass matrices, is the damage in glass matrices due to the ballistic processes caused ...
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Iron phosphate glass (IPG) is considered as a suitable matrix for the immobilization of nuclear waste containing higher concentration of Cs, rare earth, Mo and Cr. The central issue, while disposing nuclear waste in glass matrices, is the damage in glass matrices due to the ballistic processes caused by atomic displacements due to α-particles and the recoiling of heavy nuclei resulting from actinide decay. Ion irradiation produces similar kind of damage, and hence the samples are irradiated with 4 MeV O + (self) ion. The microstructural studies were carried out using transmission electron microscopy (TEM) for as-prepared, annealed and ion irradiated samples. It is observed that ion irradiation in IPG leads to the formation of nanocrystals with different phases containing Fe, P and O. Thermally activated crystallization process is ruled out based on the non-equilibrium experimental conditions. In the present experiments, stress driven crystallization mechanism was invoked. The stress, around the ion track formed during ion irradiation, is larger than the yield strength of the glass and hence, the surrounding matrix undergoes substantial deformation resulting in the formation of shear bands. Nucleation of nanocrystals is driven by the stress in the vicinity of the shear bands.
Jai Prakash; A. Tripathi; G. B. V. S. Lakshmi; V. Rigato; Jalaj Tripathi; D. K. Avasthi
Abstract
Thin metal films of Ag (~10 nm) deposited on spin coated PVC film on quartz substrate, were irradiated with 150 keV Ar ions at fluences varying from 5×10 15 to 5×10 16 ions/cm 2 and characterized with Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron ...
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Thin metal films of Ag (~10 nm) deposited on spin coated PVC film on quartz substrate, were irradiated with 150 keV Ar ions at fluences varying from 5×10 15 to 5×10 16 ions/cm 2 and characterized with Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. RBS spectra show sputtering of the Ag film. As a result of ion irradiation, isolated Ag nanoparticles are formed on the surface. The size and size distribution of Ag nanoparticles are found to be dependent on ion fluence. Contact angle measurements were carried out to study the hydrophilic nature of the surface at varying fluences. Results are explained in the framework of sputtering from the surface due to dense collision cascade resulting from Ar ion and Ag/PVC film interaction.
