Ion accelerators have a fundamental role in atomic and nuclear studies as well as in applied physics, including the modification and characterization of materials. The precise knowledge of the energy ...of accelerated ions is of utmost importance, especially for cross-section measurements or for accurate depth profiling using narrow resonances. The 3 MV Cockcroft–Walton tandem accelerator of IFIN-HH from HVEC was installed in 2012. The machine is mainly dedicated to ion beam analysis, ion implantation, and astrophysics studies at low energy. In this work, we report on the first calibration for alpha particles of the terminal voltage using a technique based on Rutherford backscattering spectrometry measurements. The energies of the α particles from a mixed spectroscopic 239Pu + 241Am α source are compared with the energies of 4He projectiles backscattered into a silicon detector by carbon and gold layers. The position of the 16O(α,α) 16O resonance around 3.038 MeV at backscattering angles of 145° and 165° was remeasured. Our results are compared with recent results reported in the literature.
•Growth of SrTiO3 films by UFPLD using 10ps pulses at 1064nm.•Crystalline nearly stoichiometric films were deposited at 0.2MHz.•A repetition rate threshold concerning crystallinity, stoichiometry and ...particle size was identified.
SrTiO3 particle-composed films were grown on Si substrates via picosecond ultrafast pulsed laser deposition. We have investigated the effect of laser pulse repetition rate (0.2–8.2MHz) and fluence (0.079–1.57Jcm−2) on the morphology, crystallinity and stoichiometry of the films. X-ray diffraction, energy dispersive X-ray spectroscopy and Rutherford backscattering spectroscopy measurements demonstrated that the as-grown films were nearly stoichiometric and composed of large particles when a pulse repetition rate of 0.2MHz was employed. However, at the higher repetition rate of 8.2MHz the particle size decreased and the stoichiometry was altered. Finally, we attribute the formation of micron-size particle-composed films to the slow translation speed in relation to the high pulse repetition rates (kHz–MHz regime).
Investigations of biogenic ferrihydrite nanoparticles produced by bacteria Klebsiella oxytoca by applying small angle X-ray scattering, synchrotron radiation diffraction and ion beam analysis methods ...are reviewed. Different experimental data processing methods are used and analyzed.
Combined PIXE and PIGE analysis was applied at the new Bucharest Tandetron to investigate biomineralization in two calcified tissues, deer antlers and femur bone. By annual loss and fast re-growth, ...antlers are a valuable model for bone as a dynamical system. Samples characterized by optical microscopy and histology were analyzed for P, Ca, F, Na, Mg, S, Cl, K, Zn, Sr by 3MeV proton simultaneous PIXE and PIGE, using a hydroxyapatite standard and other reference materials. Good correlation between methods was found for P, and the concentrations were related to biological data. Antlers showed lower mineralization than femur, with the lowest values in the third antler beam. A power function of mineralization vs. “mineral age” of antlers was found. Thus combined PIXE and PIGE of antlers may bring highly relevant insights in biomineralization research.
Magnetic nanoscale materials exhibiting the L10 tetragonal phase such as FePt or ternary alloys derived from FePt show most promising magnetic properties as a novel class of rare earth free permanent ...magnets with high operating temperature. A granular alloy derived from binary FePt with low Pt content and the addition of Mn with the nominal composition Fe57Mn8Pt35 has been synthesized in the shape of melt-spun ribbons and subsequently annealed at 600 °C and 700 °C for promoting the formation of single phase, L10 tetragonal, hard magnetic phase. Proton-induced X-ray emission spectroscopy PIXE has been utilized for checking the compositional effect of Mn addition. Structural properties were analyzed using X-ray diffraction and diffractograms were analyzed using full profile Rietveld-type analysis with MAUD (Materials Analysis Using Diffraction) software. By using temperature-dependent synchrotron X-ray diffraction, the disorder–order phase transformation and the stability of the hard magnetic L10 phase were monitored over a large temperature range (50–800 °C). A large interval of structural stability of the L10 phase was observed and this stability was interpreted in terms of higher ordering of the L10 phase promoted by the Mn addition. It was moreover found that both crystal growth and unit cell expansion are inhibited, up to the highest temperature investigated (800 °C), proving thus that the Mn addition stabilizes the formed L10 structure further. Magnetic hysteresis loops confirmed structural data, revealing a strong coercive field for a sample wherein single phase, hard, magnetic tetragonal L10 exists. These findings open good perspectives for use as nanocomposite, rare earth free magnets, working in extreme operation conditions.
•By tuning the substrate temperature one can obtain SrCuO2 films that exhibit both stable (orthorhombic) and metastable (tetragonal) phases in pure form as well as films composed of a mixture of ...tetragonal and orthorhombic phases.•SrCuO2 films exhibit a stoichiometry variation across the temperature range of the structural transformation.•The non-equilibrium nature of the growth process is the origin of the stabilization of the tetragonal (hp I) phase in SrCuO2 thin films grown on SrTiO3 substrates at low substrate temperatures.
In this work we have systematically investigated the evolution of structure and stoichiometry in SrCuO2 films grown on TiO2-terminated SrTiO3 substrates as a function of the substrate temperature. Depending on the growth temperature SrCuO2/SrTiO3 films can exhibit either a pure tetragonal high-pressure phase, or a pure orthorhombic low-pressure phase, or a mixed phase. Our results indicate that at low substrate temperatures the non-equilibrium state of the growth process is responsible for the stabilization of the metastable tetragonal high-pressure structure in SrCuO2 thin films grown on (001) SrTiO3 substrates, whose lattice matches the metastable structure. In addition, at higher substrate temperatures thermodynamics become dominant over other factors and the SrCuO2 thin films are stabilized in the thermodynamically stable orthorhombic phase.
In this work we present the deposition of amorphous SiC thin films by radiofrequency dual magnetron sputtering. The dependence of the deposited films properties over the discharges electrical power ...and the effect of hydrogenous species (H2 and/or D2) addition to main discharge gas (Ar) were investigated. Accurate elemental analysis of the samples, including detection of hydrogen and deuterium, was performed by ion beam analysis (IBA) techniques: RBS (Rutherford Backscattering Spectrometry) and ERDA (Elastic Recoil Detection Analysis). SiCx thin films with thicknesses between 1700 and 4500Å and C/Si ratio between 0.2/1 and 1.25/1 were obtained in different deposition conditions. The results prove that thin films of amorphous SiC with well controlled properties can be produced using radiofrequency dual magnetron sputtering.
This study investigates the microstructural modifications induced in cubic zirconia by He implantation at high concentration (∼4
at.%). The effect of post-implantation thermal annealing on the ...crystal stability is particularly addressed. For this purpose, three complementary analysis techniques, namely RBS/C, XRD and TEM, have been used. The structure of as-implanted crystals appears weakly defective, the damage very likely consisting of interstitial-type defects and helium-vacancy clusters. These defects induce a tensile elastic strain gradient with a depth distribution that overlaps the He depth profile. After annealing at 800
°C, a partial strain relaxation is observed, but the crystalline structure is strongly altered due to the formation of helium bubbles and elongated fractures.
Highly textured ZnO thin films were implanted with Co ions at fluences of 1 × 1016 and 1 × 1017 ions cm−2. Although their microstructure observed by analytical high-resolution electron microscopy was ...very different, SQUID magnetometer measurements showed qualitatively similar magnetic properties. In the low-fluence film, only small modifications, such as a slight amorphization, planar defects or very small (<1-1.5 nm) Co clusters, were hardly observable. Implantation at a higher fluence led to important changes in the film structure: heavy amorphization and metallic Co precipitates were identified by electron diffraction, energy dispersive x-ray spectroscopy (EDS), electron energy loss spectroscopy and scanning transmission electron microscopy spectrum imaging. EDS microanalysis additionally revealed the presence of ∼2 at% Co atoms that were likely dissolved in the ZnO lattice at the atomic level. No Co oxides or other secondary oxide phases were detected. For both implanted samples, the dimensions of Co precipitates were below the superparamagnetic limit at room temperature. Thermo-magnetization curves and magnetic hysteresis loops measured in the temperature range from 5 to 300 K indicated two superimposed magnetic regimes, one predominant above 50 K and the other below 50 K. We analysed the possible mechanisms and quantitative contributions to explain the observed magnetic behaviour at low and room temperature.
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