Search

This document is related to the implementation of Task 4.2 ‘Micro-beam upgrade at RBI Accelerator Facility’. The aim is to upgrade the two existing ion micro-beam stations by providing a precise motorized positioning system with the beam current control and device under control position monitor, as well as to demonstrate the sample cooling option for the ‘old’ micro-beam station. It has been planned that up to M23 ‘new’ ion micro-beam station will be upgraded (MS12) and that the ‘old’ micro-beam station will be upgraded in the same way before the project end.

We report on the metrological characterization of the emission from a germanium-vacancy center in diamond under a microfabricated solid immersion lens in a confocal laser-scanning microscope setup. Ge ions were implanted into a synthetic diamond at 3 MeV, and germanium-vacancy centers were then formed by subsequent annealing. Afterward, solid immersion lenses were fabricated in a focused ion beam scanning electron microscope. The photoluminescence was investigated at room temperature in terms of the spectral distribution, the excited state lifetime, the second-order correlation function, and the saturation behavior, proving simultaneous high single-photon purity and high brightness. Two methods were exploited to minimize the residual multi-photon probability: spectral filtering and temporal filtering. According to these results, we assume that Raman scattered photons and emission from neighboring color centers play an important role in the residual multi-photon emission probability. The system efficiency of the single-photon source was investigated and found to be in accordance with the value calculated from all sources of loss in the setup. The branching ratio of the germanium-vacancy center for the decay into the ground state and into metastable state was calculated. The results enable the usage of the single-photon source in future quantum radiometric experiments.

The differential cross sections of the first two proton groups of the 12 C ( 3 He ,p) 14 N reaction were determined within the 3 He energy range 1.34–2.86 MeV and for backward angles from 107o 107 o to 164 o with 2 o steps using two double sided silicon strip detectors. The results are presented in graphical form and they are also given as tables in the Appendix. Aiming to assist in the enrichment of the reaction database and the improvement of the differential cross section data quality, the determined cross sections were benchmarked with the measurement of thick target reaction yields from a pure glassy carbon target at two 3 He energies, 2.0 and 2.7 MeV. Furthermore, the data were accompanied by R-Matrix theory calculations, allowing for cross section data interpolation with sufficient accuracy.

On the sample of 84 Serbian companies which operate on Kosovo territory (Serbian enclaves) in post-conflict situation we explored which factors are crucial for their survival and success. Also, we want to find out is EU regulatory document for small enterprises helpful for them in this situation. We did not find EU document helpful in this situation. The results have confirmed that the enterprises are aware that expanding the market range is the only real and sustainable method of developing their activities. The key limiting factor in expanding the market range is the unfair competition. Furthermore, we are particularly pleased with the fact that enterprises from the northern part of Kosovo and Metohia are aware of the importance of innovative activities, and they realized that in contemporary business world it is possible to survive and grow in the market only by developing and introducing innovations. There are no universal solutions in a post-conflict situation. Search for ideal solution for developing the entrepreneur activities and it depends on the combination of social/political, institutional, cultural and economic aspects.

The charge collection efficiency (CCE) in electronic grade, single crystal chemical vapor deposition (scCVD) diamond detector was studied using different ions of the MeV energy range from room temperature down to 47 K. The measurements were performed by using the ion beam induced charge (IBIC) technique, with 0.8 MeV H+, 3 MeV He2+, 5.6 MeV Li2+, and 12.8 MeV C4+ ion beams. The total accumulated charge as a function of temperature was extracted from the measured pulse height spectra. A similar decreasing trend of the detector CCE with temperature was observed for all ion species. A plateau was observed from room temperature to 145 K followed by a sharp, step like, decrease in the temperature range of 65 K < T < 145 K. Below 65 K, the CCE reaches another plateau with small variations down to 47 K. The decrease in collected charge was observed in the same temperature window for each ion. However, the level of the CCE decrease varied. For He, Li and C, the CCE decreased to 24.7 ± 0.4 %, 23.6 ± 1.3 %, 25.9 ± 0.8 % respectively while 39.3 ± 0.8 % for H. The reduction of the CCE is in agreement with earlier reported results obtained by alpha particles which was associated with the changes in lifetime of excitons in diamond.

Percolation model with nucleation and object growth is studied by Monte Carlo simulations on a triangular lattice with point-like impurities. Growing objects are needle-like objects and self-avoiding random walk chains. In each run through the system the lattice is initially randomly occupied by point-like impurities at given concentration ρ i m p . Then the seeds for the object growth are randomly distributed at given concentration ρ. The percolation properties and the jamming densities are compared for the two classes of growing objects on the basis of the results obtained for a wide range of densities ρ and ρ i m p up to the percolation threshold for the monomer deposition on a triangular lattice. Values of the percolation thresholds θ p ∗ have lower values for the needle-like objects than for the self-avoiding random walk chains. The difference is largest for the lowest values of ρ and ρ i m p , and ceases near the values of the site percolation threshold for monomers on the triangular lattice, ρ p ∗ ≃ 0.5 . Values of the jamming coverage θ J decrease with ρ i m p for given ρ. This effect is more prominent for the growing random walk chains.

Telescope detectors have long been studied for their capability of discriminating the type of radiation detected. Silicon is the most widely used material for solid-state detectors. However, in many nuclear physics experiments and medical applications, diamond offers significant advantages due to its outstanding features, such as a near tissue equivalence, high radiation hardness and reliable operation in harsh environments. A monolithic ΔE–E diamond-based telescope was fabricated. The thicknesses of the two detection stages were 2.5 μm and 500 μm for the ΔE and E stage, respectively. The device was characterised by means of IBIC (Ion Beam Induced Charge) analysis at the Ruđer Bošković Institute ion microbeam. The detector, irradiated with different low energy ions ranging from helium to oxygen, showed good homogeneity of the response on a well-defined sensitive volume with a charge collection efficiency close to 100%. The ΔE stage showed a very good linear response on a wide range of LET values in diamond (170–3140 keV/μm). Due to its relatively low thickness, it can be successfully used as a microdosimeter. Time coincidence measurements have demonstrated the diamond telescope capability of discriminating and identifying the impinging ions. However, when the ratio between the energy deposited by the particle in the E stage and in the ΔE stage is small, the response of the E stage was observed to be affected by a cross-talk between the two stages of the device. A method to correct the E response for such effect was developed and successfully applied to the acquired data.

The application possibilities of the nuclear microprobe are constantly evolving which places new requirements on the data acquisition and microbeam control systems. MeV SIMS experiments for example, require the ability to pulse a continuous beam and steer it in the X-Y plane. For channeling RBS and STIM experiments, the sample needs to be rotated over two axes. Once it is positioned in the channeling direction, patterned irradiation may be needed. Additionally, with the evolution of digital electronics, it is now possible and sometimes preferred to perform signal processing in the digital domain as oppose to analogue signal chains in NIM modules. In this work we present the most recent upgrades to the data acquisition and control system developed at Rudjer Boskovic Institute. A data acquisition/control system based on a Xilinx Virtex 6 FPGA was developed which can evolve with the microprobe and be reconfigured for various applications. The real time reprogrammable nature of the FPGA coupled with a modular design approach, allow for the ADCs, processing algorithms and communication protocols to be interchanged and upgraded while keeping a constant user interface through the SPECTOR software package.

We experimentally discovered that Al2O3 and MgO exhibit well-pronounced nanometric modifications on the surfaces when irradiated under grazing incidence with 23 MeV I beam, in contrast to normal incidence irradiation with the same ion beam when no damage was found. Moreover, ions in these two materials produce notably different structures: grooves surrounded with nanohillocks on MgO surfaces vs. smoother, roll-like discontinuous structures on the surfaces of Al2O3. To explain these results, detailed numerical simulations were performed. We identified that a presence of the surface inhibits recrystallization process, thereby preventing transient tracks from recovery, and thus forming observable nanopatterns. Furthermore, a difference in the viscosities in molten states in Al2O3 vs. MgO explains the differences in the created nanostructures. Our results thus provide a deeper understanding of the fundamental processes of surface nanostructuring, potentially allowing for controlled production of periodic surface nanopatterns.

Random sequential adsorption of mixtures of objects of various shapes on a three-dimensional (3D) cubic lattice is studied numerically by means of Monte Carlo simulations. Depositing objects are ‘lattice animals’, made of a certain number of nearest neighbor sites on a lattice. We analyzed binary mixtures composed of shapes of equal size, n = 3, 4, 5. We concentrate here on the influence of geometrical properties of the shapes on the jamming coverage θ J and on the temporal evolution of the density θ(t). The approach of the coverage θ(t) to the jamming limit θ J is found to be exponential, θ J − θ(t) ∼ exp(−t/σ), both for the mixtures and their components. The values of the relaxation time σ are determined by the number of different orientations m that lattice animals can take when placed on a cubic lattice. The value of the relaxation time σ for a mixture is approximately twice the relaxation time for the pure component shape with a larger number m of possible orientations. Depending on the local geometry of the objects making the mixture, the jamming coverage of a mixture θ J can be either greater than both single-component jamming coverages or it can be in between these values. The first case is the most common, while in the second case, the jamming density of the mixture is very close to the higher jamming density for the pure component shapes. For a majority of the investigated mixtures, a component with a larger number of orientations m has a larger value of the fractional jamming density.

This paper examines the influence of environmental perturbations on dynamical regimes of model ecosystems. We study a stochastic lattice model describing the dynamics of a group chasing and escaping between predators and prey. The model includes smart pursuit (predators to prey) and evasion (prey from predators). Both species can affect their movement by visual perception within their finite sighting range. Non-conservative processes that change the number of individuals within the population, such as breeding and physiological dying, are implemented in the model. The model contains five parameters that control the breeding and physiological dying of predators and prey: the birth and two death rates of predators and two parameters characterizing the birth and death of prey. We study the response of our model of group chase and escape to sudden perturbations in values of parameters that characterize the non-conservative processes. Temporal dependencies of the number of predators and prey are compared for various perturbation events with different abrupt changes of probabilities affecting the non-conservative processes.

This paper describes both an experimental methodology based on the Ion Beam Induced Charge (IBIC) technique and the relevant interpretative model, which were adopted to characterize the electronic features of power diodes. IBIC spectra were acquired using different proton energies (from 1.2 to 2.0 MeV), angles of incidence, and applied bias voltages. The modulation of the ion probe range, combined with the modulation of the extensions of the depletion layer, allowed the charge collection efficiency scale to be accurately calibrated, the dead layer beneath the thick (6 micrometer) Al electrode and the minority carrier lifetime to be measured. The analysis was performed by using a simplified model extracted from the basic IBIC theory, which proved to be suitable to interpret the behaviour of the IBIC spectra as a function of all the experimental conditions and to characterize the devices, both for what concerns the electrostatics and the recombination processes., Comment: 24 pagese,10 figures

The paper reports the micron-scale investigation1 of an all-carbon detector based on synthetic single crystal2 CVD-diamond having an array of cylindrical graphitic buried-3 contacts, about 20 µm in diameter each, connected at the4 front side by superficial graphitic strips. To induce diamond-5 to-graphite transformation on both detector surface and bulk6 volume, direct-laser-writing technique was used. Laser-treatment7 parameters and cell shape have been chosen to minimize the over-8 lapping of laser-induced stressed volumes. Optical microscopy9 with crossed polarizers highlighted the presence of an optical10 anisotropy of the treated material surrounding the embedded11 graphitized columns, and non-uniform stress in the buried12 zones being confirmed with a confocal Raman spectroscopy13 mapping. Dark current-voltage characterization highlights the14 presence of a field-assisted detrapping transport mainly related15 to highly-stresses regions surrounding buried columns, as well as16 superficial graphitized strips edges, where electric field strength17 is more intense, too. Notwithstanding the strain and electronic-18 active defects, the detector demonstrated a good charge collection19 produced by 3.0 and 4.5 MeV protons impinging the diamond,20 as well as those generated by MeV β-particles emitted by 90Sr21 source. Indeed, the mapping of charge collection efficiency with22 Ion Beam Induced Charge technique displayed that only a few23 micrometers thick radial region surrounding graphitic electrodes24 has a reduced efficiency, while most of the device volume25 preserves good detection properties with a charge collection26 efficiency around 90% at 60 V of biasing. Moreover, a charge27 collection efficiency of 96% was estimated under MeV electrons28 irradiation, indicatingthe good detection activity along theburied29 columns depth

The properties of the random sequential adsorption of objects of various shapes on simple three-dimensional (3D) cubic lattice are studied numerically by means of Monte Carlo simulations. Depositing objects are "lattice animals," made of a certain number of nearest-neighbor sites on a lattice. The aim of this work is to investigate the impact of the geometrical properties of the shapes on the jamming density θ_{J} and on the temporal evolution of the coverage fraction θ(t). We analyzed all lattice animals of size n=1, 2, 3, 4, and 5. A significant number of objects of size n⩾6 were also used to confirm our findings. Approach of the coverage θ(t) to the jamming limit θ_{J} is found to be exponential, θ_{J}-θ(t)∼exp(-t/σ), for all lattice animals. It was shown that the relaxation time σ increases with the number of different orientations m that lattice animals can take when placed on a cubic lattice. Orientations of the lattice animal deposited in two randomly chosen places on the lattice are different if one of them cannot be translated into the other. Our simulations performed for large collections of 3D objects confirmed that σ≅m∈{1,3,4,6,8,12,24}. The presented results suggest that there is no correlation between the number of possible orientations m of the object and the corresponding values of the jamming density θ_{J}. It was found that for sufficiently large objects, changing of the shape has considerably more influence on the jamming density than increasing of the object size.

Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields. In this work we report on the investigation in the formation of photoluminescent (PL) defects upon MeV He implantation in diamond. Such color centers, previously reported only in electroluminescence and cathodoluminescence regime, exhibited two sharp emission lines at 536.5 nm and 560.5 nm, without significant phonon sidebands. A strong correlation between the PL intensities of the above-mentioned emission lines and the He implantation fluence was found in the 10^15-10^17 cm^{-2} fluence range. The PL emission features were not detected in control samples, i.e. samples that were either unirradiated or irradiated with different ion species (H, C). Moreover, the PL emission lines disappeared in samples that were He-implanted above the graphitization threshold. Therefore, the PL features are attributed to optically active defects in the diamond matrix associated with He impurities. The intensity of the 536.5 nm and 560.5 nm emission lines was investigated as a function of the annealing temperature of the diamond substrate. The emission was observed upon annealing at temperatures higher than 500{\deg}C, at the expenses of the concurrently decreasing neutral-vacancy-related GR1 emission intensity. Therefore, our findings indicate that the luminescence originates from the formation of a stable lattice defect. Finally, the emission was investigated under different laser excitations wavelengths (i.e. 532 nm and 405 nm) with the purpose of gaining a preliminary insight about the position of the related levels in the energy gap of diamond.

In this paper, we describe an experiment aimed to measure the physical observables, which can be used for the assessment of the radiation hardness of commercially available silicon photo diodes commonly used as nuclear detectors in particle accelerator laboratories. The experiment adopted the methodology developed during the International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP No. F11016) “Utilization of Ion Accelerators for Studying and Modelling Ion Induced Radiation Defects in Semiconductors and Insulators”. This methodology is based on the selective irradiation of micrometer-sized regions with different fluences of MeV ions using an ion microbeam and on the measurement of the charge collection efficiency (CCE) degradation by Ion Beam Induced Charge (IBIC) microscopy performed in full depletion condition, using different probing ions. The IBIC results are analyzed through a theoretical approach based on the Shockley-Read-Hall model for the free carrier recombination in the presence of ion-induced deep traps. This interpretative model allows the evaluation of the material radiation hardness in terms of recombination parameters for both electrons and holes. The device under study in this experiment was a commercial p-i-n photodiode, which was initially characterized by i) standard electronic characterization techniques to determine its doping and ii) the Angle-Resolved IBIC to evaluate its effective entrance window. Nine regions of (100 × 100) µm2 were irradiated with 11.25 MeV He ions up to a maximum fluence of 3·1012 ions/cm2. The CCE degradation was measured by the IBIC technique using 11.25 MeV He and 1.4 MeV He as probing ions. The model presented here proved to be effective for fitting the experimental data. The fitting parameters correspond to the recombination coefficients, which are the key parameters for the characterization of the effects of radiation damage in semiconductors., This work has been carried out within the IAEA coordinated research project F11016. “Utilization of Ion Accelerators for Studying and Modelling of Radiation Induced Defects in Semiconductors and Insulators”. It has been in part supported by Croatian Science Foundation (Croatia) under the project MIOBICC (No. 8127). EV acknowledges support from the project “Departments of Excellence” (L. 232/2016), funded by the Italian Ministry of Education, University and Research (MIUR) and from the experiment “ASIDI” of the Italian Institute for Nuclear Physics (INFN). The support by Australian government through the NCRIS funding scheme is acknowledged as well.

Differential cross sections for proton induced γ-ray emission from the reactions 23Na(p, p′γ)23Na (Eγ = 441 and 1636 keV) and 23Na(p, α′γ)20Ne (Eγ = 1634 keV) were measured for proton energies from 1.0 to 4.1 MeV in five different ion beam laboratories. Backscattered protons were collected simultaneously for normalization purposes, avoiding the measurement of the absolute values of the collected beam charge. The overall uncertainty was estimated to be around 7–8% for the cross section of the 441 keV γ-ray line from the 23Na(p, pγ1-0)23Na reaction, and of 8–12% for the cross section of the 1634–1636 keV γ-ray lines from the 23Na(p, αγ1-0)20Ne and 23Na(p, pγ2-1)23Na reactions. To check the possible anisotropy of the emitted 441 keV γ-ray, angular distribution measurements were performed at 1292, 1468, 1931, 2083 and 2851 keV proton energy, where sharp and well separated resonances occur in the excitation function ; moreover, in the energy range from 2.5 to 4.1 MeV proton energy, differential cross sections at 0°, 45° and 90° were measured as well.

A downsized wavelength dispersive X-ray spectrometer, employing a flat crystal and a CCD detector for use with focused ion beams has been constructed and employed to study ion beam induced chemical effects in Si K X-ray spectra from silicon and its selected compounds. By using ADP, PET and LiF(110) diffraction crystals, the spectrometer can measure X-rays in the energy range between 1.2 and 8.4 keV, with the energy resolution E/ΔE(FWHM) = 1850 on Al Kα and 1580 on Si Kα achieved with 2 MeV protons. This energy resolution enables the study of secondary effects in the K X-ray spectra of light elements, L-shell spectra of medium Z elements and M-shell spectra from heavy elements. The K X-ray spectra of silicon and selected silicon compounds were measured after excitation with 2 MeV protons and 20 MeV carbon ions focused to micrometer size. The results obtained for peak relative intensities were analyzed to study their dependence on the silicon oxidation states and effective charge on Si. The results were compared with the existing data obtained by proton, electron and photon induced ionization mechanisms, and clear differences between the ionization sources were observed. Si Kα multiple ionization satellites were studied with 20 MeV carbon ions on Si, SiO2 and SiC. The variation of apparent average L vacancy fraction pLx with effective charge on Si was studied. It has been shown that, for ionization by 20 MeV carbon ions, the relative KαL2 intensity is more sensitive to the chemical environment compared to pLx values.

The present work investigates the potential of ion beam analysis (IBA) techniques such as the Rutherford backscattering spectrometry (RBS) and particle induced X-ray emission (PIXE) using helium ions to provide quantitative in-depth elemental analysis of various types of Cu(In,Ga)Se 2 thin films. These films with a thickness of about 2 μm are used as absorber layers in photovoltaic devices with continuously increasing the performance of this technology. The preparation process generally aims to obtain an in-depth gradient of In and Ga concentrations that optimizes the optoelectronic and electrical properties of the solar cell. The measurements were performed at directly accessible single or double layered CIGS absorbers and at buried absorbers in completed thin film solar cells. The IBA data were analyzed simultaneously in order to derive best fitted profiles that match all experimental RBS and PIXE spectra. For some samples elemental profiles deduced form synchrotron based, reference free grazing incidence X-ray fluorescence analysis were compared with the IBA results and an overall good agreement was observed within quoted uncertainties.

Hypo-d–(f)-oxides of transition elements (d ≤ 5) usually feature decisive and highly pronounced effects of spontaneous adsorptive dissociation of water molecules, as the main and initial thermodynamic precondition state for the reversible latent storage and spillover properties of primary oxides (Pt–OH, Au–OH), otherwise indispensable ingredients in electrocatalysis for the oxygen electrode reactions. The higher the altervalent number (or capacity) of the former, and when mostly further advanced for the proper mixed valence hypo-d–(f)-oxide supports, the higher the overall (electro)catalytic yields primarily for cathodic oxygen reduction (ORR) and its anodic evolution (OER). In fact, cyclic voltammetry revealed the interrelated redox properties of the primary (Pt–OH) and surface (Pt═O) oxides between the cathodic hydrogen and anodic oxygen evolving limits, though the former has already been for longer known as the intermediate state from hydrogen oxidation in heterogeneous Doeberriner reaction upon Pt cat...

Electrically-active defects have a significant impact on the performance of electronic devices based on wide band-gap materials such as diamond. This issue is ubiquitous in diamond science and technology, since the presence of charge traps in the active regions of different classes of diamond-based devices (detectors, power diodes, transistors) can significantly affect their performances, due to the formation of space charge, memory effects and the degradation of the electronic response associated with radiation damage. Among the most common defects in diamond, the nitrogen-vacancy (NV) center possesses unique spin properties which enable high-sensitivity field sensing at the nanoscale. Here we demonstrate that NV ensembles can be successfully exploited to perform a direct local mapping of the internal electric field distribution of a graphite-diamond-graphite junction exhibiting electrical properties dominated by trap- and space-charge-related conduction mechanisms. By performing optically-detected magnetic resonance measurements, we performed both punctual readout and spatial mapping of the electric field in the active region at different bias voltages. In this novel "self-diagnostic" approach, defect complexes represent not only the source of detrimental space charge effects, but also a unique tool to directly investigate them, by providing experimental evidences on the conduction mechanisms that in previous studies could only be indirectly inferred on the basis of conventional electrical and optical characterization.

A detailed characterization under 90Sr β-particles and 4.5 MeV protons micro-beam of a single-crystal CVD diamond-based three-dimensional detector with surface and buried graphite electrodes is presented. Pillar contacts, 300 µm long and 30 µm diameter, were fabricated by using a femtosecond laser operating at 1030 nm wavelength and 400 fs pulse duration. Charge collected under 90Sr β-particles was measured in front and back irradiation conditions, pointing out that the pillars contribute to the charge collection. Charge collection efficiency (CCE) was measured to be up to 94% under proton beam irradiation. Results of a comprehensive study, including crossed-polarizers imaging, numerical simulation of the electric field distribution, and proton mapping, show that CCE is not affected from the stress induced by the pillar fabrication, and that the electric field strength is high enough to partially compensate for carrier recombination in the defected regions surrounding the pillars.

We report on the creation and characterization of Pb-related color centers in diamond upon ion implantation and subsequent thermal annealing. Their optical emission in the photoluminescence (PL) regime consists of an articulated spectrum with intense emission peaks at 552.1 and 556.8 nm, accompanied by a set of additional lines in the 535–700 nm range. The attribution of the PL emission to stable Pb-based defects is corroborated by the correlation of its intensity with the implantation fluence of Pb ions. PL measurements performed as a function of sample temperature (in the 143–300 K range) and under different excitation wavelengths (i.e., 532, 514, 405 nm) suggest that the complex spectral features observed in Pb- implanted diamond might be related to a variety of different defects and/or charge states. The emission of the 552.1 and 556.8 nm lines is reported at the single-photon emitter level, demonstrating that they originate from the same individual defect. This work follows from previous reports on optically active centers in diamond based on group-IV impurities, such as Si, Ge, and Sn. In perspective, a comprehensive study of this set of defect complexes could bring significant insight on the common features involved in their formation and opto-physical properties, thus offering a basis for the development of a new generation of quantum-optical devices.

In this work we present differential cross sections for γ-ray emission from the reactions 19F(p,p′γ)19F (Eγ = 110, 197, 1236 and 1349 + 1357 keV), 24Mg(p,p′γ)24Mg (Eγ = 1369 keV) and 25Mg(p,p′γ)25Mg (Eγ = 390, 585 and 975 keV). Differential cross sections were measured for proton energies from 1.95 to 3.05 MeV with a 15 keV step and beam energy resolution of 0.06%. Thin reference standard, 54.1 μg/cm2 of MgF2 deposited on thin Mylar foil with additionally evaporated 4 nm Au layer, was used as a target. The γ-rays were detected by a 20% relative efficiency HPGe detector placed at an angle of 135° with respect to the beam direction, while the backscattered protons were collected using silicon surface barrier detector placed at the scattering angle of 165°. Obtained cross sections were compared with the previously measured data available from the literature.

We report on measurements of the electrical conductivity on a two-dimensional packing of metallic disks when a stable current of ~1 mA flows through the system. At low applied currents, the conductance σ is found to increase by a pattern σ(t) = σ ∞ − Δσ E α [ − (t/τ) α ], where E α denotes the Mittag-Leffler function of order α ∈ (0,1). By changing the inclination angle θ of the granular bed from horizontal, we have studied the impact of the effective gravitational acceleration g eff = gsinθ on the relaxation features of the conductance σ(t). The characteristic timescale τ is found to grow when effective gravity g eff decreases. By changing both the distance between the electrodes and the number of grains in the packing, we have shown that the long term resistance decay observed in the experiment is related to local micro-contacts rearrangements at each disk. By focusing on the electro-mechanical processes that allow both creation and breakdown of micro-contacts between two disks, we present an approach to granular conduction based on subordination of stochastic processes. In order to imitate, in a very simplified way, the conduction dynamics of granular material at low currents, we impose that the micro-contacts at the interface switch stochastically between two possible states, “on” and “off”, characterizing the conductivity of the micro-contact. We assume that the time intervals between the consecutive changes of state are governed by a certain waiting-time distribution. It is demonstrated how the microscopic random dynamics regarding the micro-contacts leads to the macroscopic observation of slow conductance growth, described by an exact fractional kinetic equations.

Surface in and ex situ analysis have shown that in the course of cathodic oxygen reduction (ORR), all along the reversible potential range (the low slope Tafel plots, about 30 mVs/dec), nanostructured Pt electrocatalyst is covered by the interfering primary (Pt–OH) and surface (Pt═O) oxide mixture, while the higher polarization (120 mVs/dec) characterizes electrocatalytic surface deprived from these oxides and, consequently, the reaction mechanism of direct electron exchange on clean electrode surface. The substantial difference between the standard RHE (reversible hydrogen electrode) and ROE (reversible oxygen electrode), is that the former implies spontaneous hydrogen adsorption, fast H-adatoms (Pt–H) effusion and reversible electrode behavior (Pt(H2)/Pt–H/H3O+), while the latter features the strong irreversible Pt═O adsorptive strength, and which is more significant, missing the Pt–OH spillover within the critical potential range between the primary oxide adsorption/desorption peaks position and oxygen...

The aim of this paper was to investigate the possibility of using the copper anodes with high nickel content for electrolytic treatment of waste sulfuric acid copper electrolyte. Nickel content in each anode was about 10 wt. %. Lead, antimony, and tin content was within the limits ranged from 0.1 to 1.4 wt. %. Copper mass content in anodes was in the range from 86 to 90 wt. %, and was mathematical deference to 100 wt. %. Electrolytic processing was done in galvanostatic conditions at the current density of 250 A/m2, electrolyte temperature of 63 ± 2 ° C, duration of each test of 72 h. The mass of each anode was about 7 kg. The waste sulfuric acid electrolyte with concentration of 30 g dm3 Cu2+ ions and 225 g/dm3 SO4 2- ions was used as the working solution. Changing the anode mass, changing the content of copper and nickel ions in the working solution and the mass of obtained cathode deposit were the subject of discussion in this paper. The difference in weight of anode at the beginning and end of the process confirmed that the anodes are dissolved during the process. A significant reduction of Cu2+ ions concentration was achieved as well as an increase in concentration of Ni2+ ions in the working solution. Mass of cathode deposit, obtained during electrolytic refining of anode with the smallest impurity content, was greater than the mass of dissolved correspondent anode for about 2%. Mass of cathode deposit, obtained by refining the anode with the content of Pb + Sn + Sb from 1.5 to 3.5 wt. %, was less than the mass of dissolved correspondent anode by about 2 %.

International audience; Conditions for ion track formation in single crystal SrTiO3 and TiO2 (rutile) after irradiations using swift heavy ion beams with specific energies below 1 MeV/amu were investigated in this work. Rutherford backscattering spectroscopy in channeling was used to measure ion tracks in the bulk, while atomic force microscopy was used for observation of ion tracks on the surfaces. Variations in the ion track sizes and respective thresholds were observed after irradiations under random, channeling and near-channeling conditions close to normal incidence. These variations are attributed to the specifics of the electronic stopping power of swift heavy ions under the investigated conditions. In the case of ion channeling, electronic stopping power is reduced and observed ion tracks are smaller. The opposite was found under the near-channeling conditions when lowering of the ion track formation threshold was observed. We attribute this finding to the oscillating electronic stopping power with large peak values. For both materials, thresholds for bulk and surface ion track formation were found to be surprisingly close, around 10 keV nm−1. Obtained results are compared with predictions of the analytical thermal spike model.

International audience; Charged particle semiconductor detectors have been used in Ion Beam Analysis (IBA) for over four decades without great changes in either design or fabrication. However one area where improvement is desirable would be to increase the detector solid angle so as to improve spectrum statistics for a given incident beam fluence. This would allow the use of very low fluences opening the way, for example, to increase the time resolution in real-time RBS or for analysis of materials that are highly sensitive to beam damage. In order to achieve this goal without incurring the costs of degraded resolution due to kinematic broadening or large detector capacitance, a single-chip segmented detector (SEGDET) was designed and built within the SPIRIT EU infrastructure project. In this work we present the Charge Collection Efficiency (CCE) in the vicinity between two adjacent segments focusing on the interstrip zone. Microbeam Ion Beam Induced Charge (IBIC) measurements with different ion masses and energies were used to perform X-Y mapping of (CCE), as a function of detector operating conditions (bias voltage changes, detector housing possibilities and guard ring configuration). We show the (CCE) in the edge region of the active area and have also mapped the charge from the interstrip region, shared between adjacent segments. The results indicate that the electrical extent of the interstrip region is very close to the physical extent of the interstrip and guard ring structure with interstrip impacts contributing very little to the complete spectrum. The interstrip contributions to the spectra that do occur, can be substantially reduced by an offline anti-coincidence criterion applied to list mode data, which should also be easy to implement directly in the data acquisition software.

The acronym IBIC (Ion Beam Induced Charge) was coined in early 1990's to indicate a scanning microscopy technique which uses MeV ion beams as probes to image the basic electronic properties of semiconductor materials and devices. Since then, IBIC has become a widespread analytical technique to characterize materials for electronics or for radiation detection, as testified by more than 200 papers published so far in peer-reviewed journals. Its success stems from the valuable information IBIC can provide on charge transport phenomena occurring in finished devices, not easily obtainable by other analytical techniques. However, IBIC analysis requires a robust theoretical background to correctly interpret experimental data. In order to illustrate the importance of using a rigorous mathematical formalism, we present in this paper a benchmark IBIC experiment aimed to test the validity of the interpretative model based on the Gunn's theorem and to provide an example of the analytical capability of IBIC to characterize semiconductor devices., 22 pages, 7 figures

In this work we studied the influence of laser radiation on the composition, structure and morphology of WTi thin films deposited on n-type (100) silicon wafers. The films were deposited by d.c. sputtering from a 70:30 at% W-Ti target, using Ar ions, to a thickness of similar to 190 nm. Irradiation was performed with a pulsed Nd:YAG laser operating at 1064 nm, whereas the pulse duration was 150 ps. Laser fluences of 3.2 and 5.9 J/cm(2) were found to be sufficient for modification of the WTi/silicon target system. The results show: (i) ablation of WTi thin film and a Si substrate in the central zone of spots, (ii) appearance of hydrodynamic features like resolidified material, (iii) partial ablation of the WTi thin film at the periphery and (iv) appearance of thin film cracks at the far periphery. On the non-ablated areas, the laser modification induced changes in composition, such as inter-mixing of components at the WTi/Si interface with formation of silicides in both metals. Surface oxidation was the dominant process in the ablated areas, which is demonstrated by the presence of a SiO2 phase.

1 Institute of Chemical Engineering and High Temperature Chemical Processes-Patras, FORTH, 26500 Patras, Greece 2 Institute of Food Technology, Faculty of Agriculture, University of Belgrade, 11080 Belgrade, Serbia 3 Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany 4Department of Material Science and Engineering and Canadian Centre for Electron Microscopy, McMaster University, Hamilton ON, Canada L8S4M1

In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi) thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium ambient. The composition of the WTi/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology was monitored by Atomic Force Microscopy (AFM). In the experiment, typical laser output parameters were: wavelength 1064 nm, pulse duration 150 ps, and laser pulse energy 30 mJ. Surface concentrations of W and Ti, as well as the concentration of gas components nitrogen and oxygen were determinated before and after the action of laser radiation in different ambient conditions. The contents of W and Ti decreased after irradiation due to adsorbed gases from the surrounding atmosphere. After surface irradiation in the inert ambient (He), the concentrations of the components were not significantly changed. In other cases, oxygen was the dominant component at the surface, probably due to the high affinity of thin film components. Also, the morphological changes occurred at the surface of WTi, as an increase in the surface roughness and formation of the granular structures are a result of laser-induced surface oxidation and recrystallization. International Conference on Advanced Laser Technologies (ALT10), Sep 11-16, 2010, Egmond aan Zee, Netherlands

The core subject of the present paper represents the interrelated spillover (effusion) phenomena both of the primary oxide and the H-adatoms, their theory and practice, causes, appearances and consequences, and evidences of existence, their specific properties, and their alterpolar equilibria and kinetic behavior, structural, and resulting catalytic, and double layer charging features. The aim is to introduce electron conductive and d-d interactive individual and composite (mixed valence) hypo-d-oxide compounds, of increased altervalent capacity, or their suboxides (Magnéli phases), as the interactive catalytic supports and therefrom provide (i) the strong metal-support interaction (SMSI) catalytic effect and (ii) dynamic spillover interactive transfer of primary oxides (M-OH) and free effusional H-adatoms for further electrode reactions and thereby advance the overall electrocatalytic activity. Since hypo-d-oxides feature the exchange membrane properties, the higher the altervalent capacity, the higher the spillover effect. In fact, altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and then spontaneously pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3) under cathodic and/or its hydrated state (Pt/W(OH)6), responsible for Pt-OH effusion, under anodic polarization, this way establishing instantaneous reversibly revertible alterpolar bronze features (Pt/H0.35WO3 Pt/W(OH)6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured-type electrocatalysts, even of mixed-valence hypo-d-oxide structures (Pt/H0.35WO3/TiO2/C, Pt/HxNbO3/TiO2/C), have for the first time been synthesized by the sol-gel methods and shown rather high stability, electron conductivity, and nonexchanged initial pure monobronze spillover and catalytic properties. Such a unique electrocatalytic system, as the striking target issue of the present paper, has been shown to be the superior for substantiation of the revertible cell assembly for spontaneous reversible alterpolar interchanges between PEMFC and WE. The main target of the present thorough review study has been to throw some specific insight light on the overall spillover phenomena and their effects in electrocatalysis of oxygen and hydrogen electrode reactions from diverse angles of view and broad contemporary experimental methods and approaches (XPS, FTIR, DRIFT, XRD, potentiodynamic spectra, UHRTEM).

The cross-sections for the elastic scattering of alphas from natural nitrogen were measured at three laboratory scattering angles: 118°, 150° and 165° at non-Rutherford scattering energies from 2.5 to 4.0 MeV. Experimental data obtained in this work, together with all previously published data, were used for the cross-section evaluation. Model calculations with comparison and fitting to the experimental data were used for the evaluation of the cross-section. As a result of the work, the recommended cross-sections for scattering of alphas from nitrogen have been produced in the energy region of 1.6–4.6 MeV.

Thin films based on Cu(In,Ga)Se 2 are used as absorber cells in photovoltaic devices. In and Ga graded depth profiles are designed to optimize the solar cell performance. Simultaneous Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE) with 3 MeV 4 He ions were used in conjunction to determine the depth profile of all the heavy elements in Cu(In,Ga)Se 2 absorbers and complete solar cells. The RBS and PIXE data from one sample were analyzed synergistically, providing reliable depth profiles that satisfy all the data collected. An uncertainty analysis was done, probing the sensitivity of the analysis to different assumptions. The analytical possibilities of the combined RBS/PIXE alpha beam measurements of the CIGSe thin film solar cells, as well as the uncertainties induced in the quantitative methodology are discussed and critically assessed.

The lattice constants of a synthetic BaS04 and fourteen naturalbarite samples from the Kreševo area (Central Bosnia) were determinedby X-ray powder diffraction. The natural samples containedfrom 0.3 - 7.6 mole % SrS04 and negligible concentrations of Ca andPb pure (Ba,Sr)S04 solid solutions.The diffraction lines of most natural samples were broadened inreflection to those of synthetic BaS04. This results from obvious compositionalheterogeneity, e.g. the heterogeneous distribution of strontium,as is clearly observed from Sr variation patterns across a surfaceof the barite obtained by proton microprobe analysis. Nevertheless,the present values of unit-cell parameters are in agreement with thoseof synthetic (Ba,Sr)SO4 solidsolutions documented in the literature.It has been proven that the interplanar spacing d004 may be usedfor determination of thc Sr content of natural barites; the absoluteerror varies from ±O.3 mole % SrS04 (for homogeneous samples havingthe difrraction line 004 clearly resolved in spectral doublet components) up to ±O.5 mole % SrS04 (for the samples with compositionalheterogeneity having a broadened and relative poorly defined diffractionline 004).

New striking prospects both in low and medium temperature polymer electrolyte membrane fuel cell (PEMFC) and in water electrolysis (WE) have been opened by the interactive supported individual (Pt) or prevailing hyper-d-electronic nanostructured metal clusters (WPt3, NbPt3, HfPd3, ZrNi3), grafted upon and within high altervalent capacity hypo-d-oxides (WO3, NbO2, TaO2, TiO2) and their proper mixed valence compounds, to create a novel type of alternating polarity (alterpolar) interchangeable composite electrocatalysts for hydrogen and oxygen electrode reactions. Whereas in aqueous media Pt (Pt/C) features either chemisorbed catalytic surface properties of Pt−H or Pt═O, missing any effusion of other interacting species, a new generation of composite SMSI (strong metal−support interaction) electrocatalysts in condensed wet state primarily characterizes interchangeable extremely fast reversible spillover of either H-adatoms or the primary oxides (Pt−OH, Au−OH) or the invertible bronze type behavior of these s...

Electrocatalytic peaks from potentiodynamic spectra for relevant electrode reactions have been employed to assess decisive and most important diagnostic criterions and parameters in the electrochemical promotion of heterogeneous catalysts (EPOC) and electrocatalysts. More specifically, the anodic oxidation of formaldehyde by the spillover supplied primary oxide of Pt (Pt-OH), both of them proceeding simultaneously as the fast reversible electrode processes of rather high faradaic yields, was investigated to estimate the relevance of catalytic peaks in cyclic voltammetry for the electrochemical promotion. In the same sense, catalytic potentiodynamic peaks have been used to prove and assess the entire spillover (or effusion) effect both of H-adatoms and the primary oxide itself, too, otherwise decisive for some significant electrochemical oxidation processes, such as CO tolerance and kinetics in the cathodic oxygen reduction (ORR), including electrocatalytic features of the latter, as the one of most important electrode reactions in aqueous media. The UPD and OPD spillover double layer charging and discharging properties of the primary oxide (M-OH), interrelated with the interactive self-catalytic effect of dipole-oriented water molecules, has also been pointed out. There has also been inferred that altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3) under cathodic, and/or its hydrated state (Pt/W(OH)6), responsible for Pt-OH effusion under anodic polarization, this way establishing reversibly revertible alterpolar features (Pt/H0.35WO3 ⇔ Pt/W(OH)6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured type electrocatalysts, even of mixed hypo-d-oxide structure (Pt/H0.35WO3/TiO2/C, Pt/HxNbO3/TiO2/C), have for the first time been synthesized by the sol–gel methods and shown rather high stability, distinctly pronounced electron conductivity and non-exchanged initial pure mono-bronze spillover and catalytic properties.