Ion beam induced modification and nanostructures formation in thin SiC/Pd films on c-Si substrate

Ion beam induced modification of thin metallic films is an emerging approach to grow metallic nanoparticles controllably. Modification of thin solid films is helpful in fabricating arrays of nanoscale particles for electronic and photonic devices and for the catalyzed synthesis of nanotubes and nanowires. In this work, the modification and nanostructures formation over the surface of SiC/Pd thin films of 15 and 45 nm thicknesses, grown on crystalline Silicon (c-Si) substrate by electron beam deposition, upon ion irradiation, have been investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Rutherford backscattering spectrometry (RBS), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. The SiC/Pd bilayer films were irradiated with 100 keV Ar+ ions at fluences of 1 × 1015 and 5 × 1015 ions/cm2 at room temperature. The surface morphology from SEM analysis showed the formation of nanoparticles that were interconnected after irradiation. The RBS and EDS results confirmed the presence of Pd, C, O and Si. While the Raman spectrum of the pristine sample displayed only a sharp peak at 520 cm−1 characteristic to c-Si substrate, the spectra of the irradiated sample red-shifted to lower wavenumbers indicating the appearance of Si nanocrystals. Hence, ion beam irradiation is a promising method for the fabrication of SiC nanostructures on c-Si substrate

Evaluation of diffusion parameters and phase formation between tungsten films and glassy carbon

Thin films of tungsten (W) were deposited on glassy carbon (C) substrates using a magnetron sputtering system. The as-deposited samples were annealed isothermally under vacuum at temperatures ranging from 673 to 1273 K. The structural changes due to thermal annealing were monitored by Rutherford backscattering spectrometry (RBS) and grazing incidence X-ray diffraction (GIXRD). RUMP software was used to simulate the RBS spectra. The thickness of W thin films deposited, atomic composition of deposited layer and the intermixed layer growth were deduced from the RUMP simulation results. The GIXRD analysis showed that carbide formation was first observed at annealing temperature of 1173 K. The kinetics of the solid-state interaction was found to be diffusion controlled at the interface between W and C. The activation energy for the diffusion of C in W was estimated as 2.23 eV. The XRD results showed that the average crystallite size of the as-deposited W film was 9.77 nm. It increased with annealing temperature up to 18.05 nm at 1173 K. The first carbide phase observed was W2C in the sample annealed at 1173 K, while WC was the dominant carbide phase at 1273 K. The stability of W/C system under heat treatments below 1073 K suggests that this system has a promising application for long-term structural integrity of dry cask storage devices.http://www.journals.elsevier.com/vacuumhj2021Physic

The influence of helium-induced defects on the migration of strontium implanted into SiC above critical amorphization temperature

The presence of radiation-induced defects and the high temperature of implantation are breeding grounds for helium (He) to accumulate and form He-induced defects (bubbles, blisters, craters, and cavities) in silicon carbide (SiC). In this work, the influence of He-induced defects on the migration of strontium (Sr) implanted into SiC was investigated. Sr-ions of 360 keV were implanted into polycrystalline SiC to a fluence of 2 × 1016 Sr-ions/cm2 at 600°C (Sr-SiC). Some of the Sr-SiC samples were then co-implanted with He-ions of 21.5 keV to a fluence of 1 × 1017 He-ions/cm2 at 350°C (Sr + He-SiC). The Sr-SiC and Sr + He-SiC samples were annealed for 5 h at 1,000°C. The as-implanted and annealed samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and Rutherford backscattered spectrometry (RBS). Implantation of Sr retained some defects in SiC, while co-implantation of He resulted in the formation of He-bubbles, blisters, and craters (exfoliated blisters). Blisters close to the critical height and size were the first to exfoliate after annealing. He-bubbles grew larger after annealing owing to the capture of more vacancies. In the co-implanted samples, Sr was located in three regions: the crystalline region (near the surface), the bubble region (where the projected range of Sr was located), and the damage region toward the bulk. Annealing the Sr + He-SiC caused the migration of Sr towards the bulk, while no migration was observed in the Sr-SiC samples. The migration was governed by “vacancy migration driven by strain fileds.

Carbon ion-beam-induced modification in structural and electrical properties of ZnO nanowires

Zinc oxide nanowires (ZnO NWs) have an efficacious place in nanoworld due to their tremendous properties and applications. In the present work, structural and electrical properties of ZnO NWs have been modified by carbon (C) ions- beam irradiation. With ion-beam energy of 0.8MeV, the physical behaviors of NWs have been studied under different doses from 1×1012 to 1×1014 ions/cm2. The microstructural and Raman spectroscopy studies showed that the wurtzite crystal structure of the ZnO NWs has been changed into disordered amorphous one under high C ion doses. Whereas, the XRD results showed that Zn nanoparticles are fabricated at high C ion-beam irradiation on ZnO NWs. Scanning electron microscopy (SEM) depicts the formation of cross junctions and parallel junctions between ZnO NWs after C ion irradiation. DC conductivity measurements have confirmed that the conductivity of NWs decreases with increase in C ion doses. It is concluded that the lattice defects significantly contribute to decrease in the conductivity of ZnO NWs

Investigating the structural modifications in LaAlYbCuO

In this research, we seek a new superconducting candidate LaAlYbCuO based on the need to improve upon the lanthanum cuprates framework. LaAlYbCuO high temperature superconductor was prepared by standard solid-state reaction. The characterization was done by the X-ray powder diffraction technique, Scanning Electron Microscopy (SEM) and Rutherford Backscattering Spectrometry (RBS). The analysis of the images was done using Match, Vesta, SRIM, CERN-Root, OMDAQ and Gwydion software. The XRD refinements show that LAYbCO has orthorhombic structure with unit cell as a = 3.865 Å, b = 3.865 Å, c = 19.887 Å. The specimen had theta correction of 0.19891°. The ratio of electron to phonon production in LAYbCO is approximately 999:1. However, this does not rule-out the possibility of electron-phonon interaction. The elemental composition of LAYbCO is given as La1.35Al3.97 Yb6.80Cu6.80O15 at Q-factor – 0.033, Chi-square – 0.6057 and dMax – 173. The new LAYbCO framework showed high chemical homogeneity. It was discovered that natural inclination of the atomic structure is quite important for structural interpretations. Keywords: Cuprates, Superconductor, Structure, Lanthanum, Structural modulatio

Measurement of L-shell X-ray production cross sections in 89Y, 158Gd and 209Bi due to 0.3 MeV/u – 1.0 MeV/u 12C ions

Please read abstract in the article.The University of Pretoria, Tshwane University of Technology and iThemba LABS (National Research Foundation of South Africa).https://www.elsevier.com/locate/apradiso2023-09-07hj2022Physic

Semi-empirical parameterization of HI/p L-shell X-ray production cross section ratios in Bi for Heavy Ion PIXE

Abstract Quantitative analysis of materials from Heavy Ion PIXE spectra remains impeded by the lack of reliable X-ray production cross section (XPCS) data. Although efforts at experimental Heavy Ion induced XPCS measurements still continue, Multiple Ionisation (MI) effects, which are not fully described by theory, render simulations of heavy ion PIXE data unreliable for large Z1/Z2 collisions, especially at low energies. This is also exacerbated by the random selection of projectile-target combinations for measured and reported experimental data available to validate theory. This study explored heavy ion induced X-ray production cross section deviations from those induced by protons at the same ion velocity. This enabled evaluations of the degree to which cross sections are enhanced through MI effects, with the aim of predicting XPCS due to heavy ion impact. The evaluation was carried out through the scaling of experimental heavy ion to theoretical proton cross section ratios (R), which were then used for the interpolation of XPCS in the same target element for ‘missing’ projectiles within the range of evaluation. Here we present measurements of heavy ion induced total L-shell XPCS in Bi, carried out to determine HI/p MI induced deviations due to C, F, Cl and Ti projectiles at an ion velocity range of (0.2–1.0) MeV/nucleon