Elastic Backscattering Research Articles

Elastic backscattering measurments for 6,7Li+58Ni, 6,7Li+116,120Sn, 6,7Li+208Pb at near barrier energies

We have performed, elastic backscattering measurements for the weakly bound nuclei 6,7Li on the medium and heavy mass targets 58Ni, 116,120Sn, 208Pb at sub- and near-barrier energies (0.6 to 1.3 EC.b.). Excitation functions of elastic scattering cross sections have been measured at 160O and 170O and the corresponding ratios to Rutherford scattering and relevant barrier distributions have been extracted. These measurements will complement recent work on a 28Si target for probing the potential at sub- and near barrier energies and relevant reaction mechanisms.

Deuterium inventory determination in beryllium and mixed beryllium-carbon layers doped with oxygen

Since the largest area of the JET first wall is composed of beryllium, it is expected that nuclear fuel is largely retained in beryllium-based co-deposits with low amounts of carbon. Co-deposited layers obtained in the laboratory, with similar stoichiometry with the ones found in JET ITER-like wall (ILW) experiments, can provide complementary information regarding the hydrogen isotopes inventory and release behaviour.We report on the analysis of the beryllium-based layers deposited by the direct current magnetron sputtering method on pure tungsten and silicon substrates. The thickness of studied layers with various amounts of deuterium, oxygen, and carbon was between 2 and 7 μm. Samples from the same batch were distributed to different laboratories and characterised by various analytical methods. Scanning electron microscopy was applied to determine the exact thickness, data from elastic backscattering spectrometry and nuclear reaction analysis to profile the depth content of light elemental species as deuterium, and thermal desorption spectroscopy to quantify the amount of deuterium and also to observe release kinetics.The main finding is that a high amount of deuterium, from 8 at.% up to 28 at.%, can be retained in the films. Deuterium release at a heating rate of 0.125 °C/s reached its maximum intensity at peaks of various widths and shape, which appeared at temperatures from 340 °C up to 660 °C, depending on the thickness, the layer stoichiometry and deposition parameters.

Studies of bronze corrosion phenomena by EBS and complementary techniques

Two binary bronze alloys were investigated in order to clarify the development of corrosion products on bronze exposed to chloride corrosive media. Bronzes were prepared by magnetron sputtering deposition on glass to create highly uniform and smooth bronze layers.The main goal was to monitor corrosion phenomena in the first and the most pronounced period of corrosion layer formation in duration of 11 days. For this purpose Ion Beam Analysis (IBA), i.e. Elastic Backscattering Spectrometry (EBS) with 2 MeV protons and 1.5 MeV Li beams were used to monitor the general stoichiometry and thicknesses of the corrosion product layers for different aging parameters. Simultaneously, Proton-Induced X-ray Emission Spectroscopy (PIXE) was used in addition to ATR-FTIR and Raman measurements to find out if, beside copper oxides, other species were present in the corrosion layer as well.

Differential elastic backscattering cross-sections of the 1–2.4 MeV deuterons on sodium

The 23Na(d,d0)23Na elastic scattering differential cross-sections were measured in the energy range Ed,lab = 1060–2400 keV for elastic backscattering spectrometry (EBS) purposes. Thin sodium targets were used, made by evaporating Na2O powder on self-supporting carbon foils, with an ultra-thin Au layer on top for normalization purposes. The measurements were made with deuteron beam energy steps of 20 or 30 keV and for the laboratory scattering angles of 140°, 150°, 160°, and 170°. The determined cross-section datasets were benchmarked using a thick NaCl target at the deuteron energies (1110, 1320, 1500, 1820 keV) and at scattering angles 140°, 150°, 160° and 170°.

Differential elastic scattering cross sections for deuterons on 9Be, at energies and angles suitable for elastic backscattering spectroscopy

The differential cross sections of the 9Be(d,d0) elastic scattering were determined in the present work in the energy range of Ed,lab = 1600–2200 keV in variable steps, mainly 20 keV at five backscattering angles (120°, 140°, 150°, 160° and 170°). The measurements were performed at the 5.5 MV TN11 HV Tandem Accelerator of the N.C.S.R. “Demokritos” implementing a high precision goniometer. The target used was a thin Si3N4 substrate with a beryllium layer on top. The obtained differential cross section values are compared to the ones existing in literature and the observed similarities and discrepancies are discussed.

In-situ composition analysis of photochromic yttrium oxy-hydride thin films under light illumination

In this work, we investigate the chemical composition of a reactively sputtered photochromic YHxOy thin film by non-destructive ion beam-based techniques, i.e., Rutherford Backscattering Spectrometry, Particle-Induced X-Ray Emission, Time-of-Flight/Energy coincidence Elastic Recoil Detection Analysis and Elastic Backscattering Spectrometry. To enhance the accuracy of the analysis, the set of spectra was evaluated in an iterative self-consistent approach. This procedure resulted in high-resolution depth profiles of the chemical composition and revealed a thin oxygen-rich-layer on the surface, which apparently does not act as a self-passivation layer. In the film, the concentration of Y remains practically constant, whereas O replaces H during the oxidation process. In-situ light illumination was performed during the compositional analysis in a high vacuum setup. The results from these measurements demonstrate that, for these samples, the induced reversible photochromism is not linked to any detectable change in the bulk composition of the film and can thus take place even in a vacuum environment.

Electron elastic backscattering probability and inelastic mean free path

We study the angular distribution of electron elastic backscattering probability, using the Oswald–Kasper–Gaukler (OKG) model and Monte Carlo simulation. The present results are consistent with experimental data and other theoretical calculations. We also propose an approach that makes the OKG model applicable to determine electron inelastic mean free paths for compounds. We apply the OKG model with the proposed approach to zinc oxide (ZnO) and cerium dioxide (CeO2).

Accurate high-resolution depth profiling of magnetron sputtered transition metal alloy films containing light species: A multi-method approach

We present an assessment of a multi-method approach based on ion beam analysis to obtain high-resolution depth profiles of the total chemical composition of complex alloy systems. As a model system we employ an alloy based on several transition metals and containing light species. Samples have been investigated by a number of different ion-beam based techniques, i.e., Rutherford Backscattering Spectrometry, Particle-Induced X-ray Emission, Elastic Backscattering Spectrometry and Time-of-Flight/Energy Elastic Recoil Detection Analysis. Sets of spectra obtained from these different techniques were analyzed both independently and following an iterative and self-consistent approach yielding a more accurate depth profile of the sample, including both metallic heavy constituents (Cr, Fe and Ni) as well as the rather reactive light species (C, O) in the alloy. A quantitative comparison in terms of achievable precision and accuracy is made and the limitations of the single method approach are discussed for the different techniques. The multi-method approach is shown to yield significantly improved and accurate information on stoichiometry, depth distribution and thickness of the alloy with the improvements being decisive for a detailed correlation of composition to the material properties such as corrosion strength. The study also shows the increased relative importance of experimental statistics for the achievable accuracy in the multi-method approach.

Elastic backscattering as a method for the measurement of the integral lithium content in thin films on fusion-relevant substrates

Different ion beam analysis techniques for the study of thin lithium-containing layers on top of fusion relevant materials are discussed and compared to each other. Elastic backscattering analysis (EBS) with protons is determined to be one of the most promising techniques and allows measurements of Li layers with thicknesses from ∼100 nm up to ∼600 μm, as shown by SIMNRA simulations. The best sensitivity for thin films (∼100 nm) can be achieved using 4 MeV protons with 170° scattering detection angle for layers on Mo and W substrates, and 2 MeV for C substrates. Experimentally EBS measurements were successfully tested for Li films with thicknesses from ∼50 nm up to ∼400 nm after air exposure. The Li films become strongly inhomogeneous and require averaging over multiple measurements in nearby areas. This necessitates averaging over multiple nearby measurement points, and limits the overall precision of the measurement.

Optical and electrical properties of MoO2 and MoO3 thin films prepared from the chemically driven isothermal close space vapor transport technique

Chemically—driven isothermal close space vapour transport was used to prepare pure MoO2 thin films which were eventually converted to MoO3 by annealing in air. According to temperature-dependent Raman measurements, the MoO2/MoO3 phase transformation was found to occur in the 225 °C–350 °C range while no other phases were detected during the transition. A clear change in composition as well as noticeable modifications of the band gap and the absorption coefficient confirmed the conversion from MoO2 to MoO3. An extensive characterization of these two pure phases was carried out. In particular, a procedure was developed to determine the dispersion relation of the refractive index of MoO2 from the shift of the interference fringes of the used SiO2/Si substrate. The obtained data of the refractive index was corrected taking into account the porosity of the samples calculated from elastic backscattering spectrometry. The Debye temperature and the residual resistivity were extracted from the electrical resistivity temperature dependence using the Bloch–Grüneisen equation. MoO3 converted samples presented a very high resistivity and a typical semiconducting behavior. They also showed intense and broad luminescence spectra composed by several contributions whose temperature behavior was examined. Furthermore, surface photovoltage spectra were taken and their relation with the photoluminescence is discussed.

First results of the differential cross sections of 9Be(d,d0) at energies and angles suitable for Elastic Backscattering Spectroscopy

The differential cross sections of the 9Be(d,d0) elastic scattering were determined in the present work in the energy range of Ed,lab = 740 - 2200 keV in variable steps, mainly 20 keV at five backscattering angles (120o, 140o, 150o, 160o and 170o). The measurements were performed at the 5.5 MV TN11 HV Tandem Accelerator of the N.C.S.R. “Demokritos” implementing a high precision goniometer. The target used was a thin Si3N4 target with a Beryllium layer on top. The obtained differential cross section values are compared to the ones existing in literature and the observed similarities and discrepancies are discussed.

Helical edge transport in the presence of a magnetic impurity: The role of local anisotropy

Helical edge modes of 2D topological insulators are supposed to be protected from time-reversal invariant elastic backscattering. Yet substantial deviations from the perfect conductance are typically observed experimentally down to very low temperatures. To resolve this conundrum we consider the effect of a single magnetic impurity with arbitrary spin on the helical edge transport. We consider the most general structure of the exchange interaction between the impurity and the edge electrons. Moreover, for the first time, we take into the account the local anisotropy for the impurity and show that it strongly affects the backscattering current in a wide range of voltages and temperatures. We show that the sensitivity of the backscattering current to the presence of the local anisotropy is different for half-integer and integer values of the impurity spin. In the latter case the anisotropy can significantly increase the backscattering correction to the current.

Ion beam measurements for the investigation of TiN thin films deposited on different substrates by vacuum arc discharge

Titanium nitride thin films were deposited on different substrates using vacuum arc discharge system. Simultaneous ion beam analysis measurements including elastic backscattering (EBS) and nuclear reaction analysis (NRA); were applied for both composition analysis and thickness measurements of the prepared TiN films. Experimental conditions have been optimized to avoid overlapping of peaks of different nuclear reactions products, especially those related to interaction between ion beam and light elements present in totally different substrates. Independent compliment measurements utilizing time-of-flight elastic recoil detection analysis (TOF-ERDA), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) measurements were also applied to verify the experimental findings obtained by EBS and NRA measurements. The results have shown that all prepared TiN films have N/Ti ratio of around 1, with low levels of contamination elements.

Non Rutherford elastic scattering to measure energy loss of H2 ions in aluminium

In this contribution, the presence of vicinage effects is demonstrated for H2+ ions slowing down in 20 nm thick aluminium target, using the 1.735 MeV resonance of 12C(p, p)12C elastic scattering. The stopping power ratio is deduced from the measured Elastic Backscattering Spectrometry (EBS) energy spectra of H+ and H2+ ions using the simulation code IBA DataFurnace. An enhancement of 30% is found in the energy loss of the H2+ ions as compared to the atomic ones. The influence of the Coulomb explosion on the energy loss straggling was also examined. This is evaluated for 100 nm thick target by adjusting the energy loss and the straggling parameters while processing the experimental data. A theoretical treatment, based on the Lindhard dielectric formalism generalized by N.R. Arista to molecular ions, was used to calculate the stopping power ratio for aluminium for comparison.

Analysis of retained deuterium on Be-based films: Ion implantation vs. in-situ loading

Pure Be, Be-O and Be-O-C thin coatings were deposited using high-power impulse magnetron sputtering (HiPIMS) with and without incorporation of deuterium. The coatings produced without deuterium were implanted afterwards with 15 keV 2H+ ion beams with a fluence limited to 2 × 1017 ion/cm2 in order to mitigate the damage imposed by ion irradiation and prevent a fast gas release. The as-deposited and as-implanted coatings were analysed by IBA techniques, namely by elastic and Rutherford backscattering spectrometries (EBS and RBS, respectively), nuclear reaction analysis (NRA) and by time-of-flight elastic recoil detection analysis (ToF-ERDA). Despite distinct deuterium depth profiles in the implanted samples, the results show that for the present ion implantation and deposition parameters, similar retained amounts are revealed in the films loaded by ion implantation or during the HiPIMS deposition, assuring ion implantation as a competitive and reliable method for fuel incorporation in thin Be-based films for retention studies in controlled conditions.

Analysis of Roman Imperial coins by combined PIXE, HE-PIXE and μ-XRF

Development of non-destructive or micro-invasive scientific diagnostic techniques gained an outmost importance in the field of Cultural Heritage, contributing to assess authenticity, provenience and age of the objects, as well as supplying additional information to art conservators, to accomplish suitable restoring and preservative procedures. However, each diagnostic technique has its own advantages and limitations, thus in many cases the optimal sample characterization requires a synergy between different analytical approaches.In this context, Particle Induced X-ray Emission (PIXE) and high energy (HE) PIXE with 3 MeV and 17 MeV proton beams respectively, Elastic Backscattering Spectrometry (EBS) and micro X-Ray Fluorescence (μ-XRF) techniques were applied in a multi-analytical approach to characterize the composition of the artifacts. The analysed samples were four Roman Imperial coins belonging to different periods between 41 A.D. and 4 B.C.The employed Ion Beam Analysis (IBA) and XRF provided comparable quantitative results relative to the main sample elemental composition. The obtained results vary significantly from one coin to the other, depending on the production date and place, and on the conservation conditions.

Composition dependent microstructure and optical properties of boron carbide (BxC) thin films deposited by radio frequency-plasma enhanced chemical vapour deposition technique

BxC thin films were deposited on silicon (100) and sodalime glass substrates using Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) technique, at different substrate self-bias varying from -100V to -250V. Optical property, structure and stoichiometry of the films were determined by spectrophotometry, X-ray diffraction and proton elastic backscattering spectrometric measurements respectively to investigate the effect of film composition on microstructure and optical properties. Film refractive index at a typical wavelength of 400 nm increased from 1.87 to 1.97 on account of increasing packing density of the films with substrate self- bias. Decrease in direct and indirect optical band gap with increasing substrate self-bias, has been explained on the basis of compositional variation i.e. boron/carbon stoichiometric ratio. Finally, soft X-ray reflectivity in the wavelength range of 40 Å–360 Å has been measured to explore its potential for application as optical material in this region of electromagnetic spectrum.

Micro ion beam analysis for the erosion of beryllium marker tiles in a tokamak limiter

Beryllium limiter marker tiles were exposed to plasma in the Joint European Torus to diagnose the erosion of main chamber wall materials. A limiter marker tile consists of a beryllium coating layer (7–9 μm) on the top of bulk beryllium, with a nickel interlayer (2–3 μm) between them. The thickness variation of the beryllium coating layer, after exposure to plasma, could indicate the erosion measured by ion beam analysis with backscattering spectrometry. However, interpretations from broad beam backscattering spectra were limited by the non-uniform surface structures. Therefore, micro-ion beam analysis (μ-IBA) with 3 MeV proton beam for Elastic backscattering spectrometry (EBS) and PIXE was used to scan samples. The spot size was in the range of 3–10 μm. Scanned areas were analysed with scanning electron microscopy (SEM) as well. Combining results from μ-IBA and SEM, we obtained local spectra from carefully chosen areas on which the surface structures were relatively uniform. Local spectra suggested that the scanned area (≈600 μm × 1200 μm) contained regions with serious erosion with only 2–3 μm coating beryllium left, regions with intact marker tile, and droplets with 90% beryllium. The nonuniform erosion, droplets mainly formed by beryllium, and the possible mixture of beryllium and nickel were the major reasons that confused interpretation from broad beam EBS.

Applications of laser-induced breakdown spectroscopy for cultural heritage: A comparison with X-ray Fluorescence and Particle Induced X-ray Emission techniques

With the aim to establish advantages and limitations of techniques commonly employed for material characterization of Cultural Heritage objects, we performed comparative measurements by LIBS, X-ray Fluorescence (XRF) and Particle Induced X-ray Emission (PIXE) on four typologies of materials. The samples include: 1) egg tempera pigments on gypsum ground; 2) oil paints on gypsum ground with light or dark imprimitura; 3) fragments of decorated glazed ceramic, and 4) ancient Roman coins. The optimal choice of an analytical instrument depends also on the sample type, its dimensions and transportability, and for these reasons our measurements involved two types of instruments per technique. The LIBS probing was done by a table-top instrument (on coins and ceramics) and by a stand-off system at distance of 9.5 m (on pigments). The XRF measurements involved a laboratory micro-XRF system (on coins) and a portable instrument (on pigments and ceramics). The PIXE analyses were obtained by TOP-IMPLART accelerator at ENEA Frascati, using a low energy line that produces the proton beam with adjustable energy between 3 and 7 MeV (used for the pigments and ceramics), and by INFN-LABEC system with proton energy of 3 MeV and complemented by Elastic Backscattering Spectrometry (EBS), for coin samples. Results relevant to quantitative analysis of major sample constituents, identification of trace components, and stratigraphy are reported and discussed for the examined typologies of samples.

Depth profiling of titanium nitride thin films deposited on stainless steel utilizing combined EBS and NRA techniques

Abstract Composition and depth profiling of titanium nitride thin films deposited on stainless steel using vacuum arc discharge device have been determined. A combination of two ion beam analysis techniques has been applied to allow accurate quantification of nitrogen in the prepared titanium nitride thin films. These include elastic backscattering (EBS) spectrometry together with nuclear reaction analysis (NRA) technique utilizing 14N(α,p0)17O nuclear reaction, both performed at resonance energy for incident alpha beam of 4500 keV. They were applied simultaneously, using two independent charged particle detectors, one is dedicated for combined EBS/NRA measurements and the other for pure NRA one. Experimental conditions have been carefully optimized to avoid overlapping of peaks of the two spectra correspond to each reaction. Novel Multi-SIMNRA software has been utilized to enable simultaneous elemental depth profile determination of both data sets. Experimental setup of the in-vacuum system has been carefully characterized. Independent complement measurements utilizing scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) were also applied to verify the experimental findings obtained by combined EBS and NRA techniques. The results have revealed N/Ti ratio of around 1 for the prepared films, with low levels of contamination elements. Finally, X-ray diffraction (XRD) measurements have demonstrated TiN structure with low oxygen contamination.