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Fundamentals of surface and thin film analysis
... The surface and subsurface composition of the etched layer on the Pt−Pd−Rh−Ru gauze after its operation in NH3 oxidation was investigated using XPS and energy-dispersive X-ray spectroscopy (EDS). SEM, EDS and XPS, which strongly differ in the effective depth of analysis [23,24], were applied to analyze the chemical composition of a ca. 5 nmthick surface layer and the subsurface region to a depth up to ca. 500 nm on Pt−Pd−Rh−Ru gauzes used in the oxidation of NH3 (see below Materials and Methods). Figure 3а, the XPS spectrum obtained for a 1 × 1 mmregion of the gauze contains XPS peaks of Pt4f, C1s, Rh3d+Pt4d, Pd3d, Rh3p and O1s. ...
... The present work is the first comparative study where the chemical compositions of the fresh Pt−Pd−Rh−Ru gauze and also the back and frontal sides of such gauze after NH3 oxidation at 1133 K were investigated by methods that are highly sensitive to the surface (XPS) and subsurface (EDS) layers. For XPS, the depth of analysis is ca. 5 nm [24], while for EDS this parameter is much higher and equal to ca. 500 nm for the alloy at Е0 = 20 keV [18]. According to the data obtained by the indicated methods ( Figures 5,7), the surface and subsurface layers of the tested Pt−Pd−Rh−Ru gauzes have strongly different concentrations of the detected elements. ...
... SEM, EDS and XPS applied in this work have different effective depths of analysis [23,24] because they are based on recording the radiation generated in subsurface layers of different thicknesses. SEM images were obtained in the secondary electron (SE) mode with emission of electrons from the surface layer with a thickness ≤5 nm [23]. ...
High-temperature oxidation of NH3 on Pt alloy gauzes to NO is widely employed in industry for the production of HNO3, which is used to obtain agricultural fertilizers. Particular attention is paid now to the investigation of the chemical composition of gauzes used in NH3 oxidation. X-ray photoelectron and energy-dispersive X-ray spectroscopies with the depth of analysis ca. 5 nm and ca. 500 nm were applied to investigate the chemical composition of surface and subsurface layers of the new and used in NH3 oxidation with air at T = 1133 K Pt−Pd−Rh−Ru catalytic gauzes (81, 15, 3.5, 0.5 wt.%, respectively). For all the gauzes, adsorption (ОНad, COad), graphitic (Сgr) and oxide (Rh2O3) films were found on the surface of the metallic alloy. Under these films, Cab, Nab and Oab atoms absorbed in the subsurface layers were detected on the gauzes used in NH3 oxidation. The obtained data testify to the penetration of Oab and Nab atoms into deeper layers of the alloy during etching with elevation of the catalyst temperature. Oab atoms were accumulated predominantly on dislocations, etch pits and grain boundaries, whereas Nab atoms intercalated mostly into interstitial sites of the alloy lattice.
... These changes occur at the cost of the energy loss suffered by the charged particle along its trajectory. The various modes of energy loss process are as follows [50,51]: ...
... A simplified classical treatment [50,51] for the evaluation of electronic energy loss rate (dE/dx) Elec. is as follows. ...
... and b max corresponds to the minimum energy transferred to the target atom which can be taken to be equal to the displacement energy (I dis ) required to remove an atom. Accordingly, the values of b max and b min can be obtained [50,51]. ...
The main interest of this chapter is to understand the fundamental energy loss processes through which incident energetic heavy ions lose their energies in the stopping medium. Fundamentals of ion interaction with matter are discussed where various modes of energy loss processes are explained. In the context of non-relativistic heavy ions, the contribution due to two types of energy loss modes, i.e., nuclear energy loss and electronic energy loss, is discussed in detail. Comparison between nuclear energy loss and electronic energy loss as a function of ion’s energy for Cu ion in Si target is shown. The fundamental Bohr energy loss equation is derived and extended by incorporating various correction terms. The most commonly used semi-empirical/empirical type energy loss formulations (Lindhard et al., Northcliffe and Schilling, Ziegler et al., Paul and Schinner, Huber et al., and Diwan et al.) are briefly introduced. Bragg’s rule, which determine the energy loss in polymers/compounds, is discussed. Finally, the importance of energy loss is highlighted.
... Quantitative analysis was performed using the internal standards contained in the spectrometer database. The SEM and EDS methods have different effective penetration depths [21,22] as they are based on the recording of radiation generated in the subsurface layers of different thicknesses. The SEM method was used to record microscopic images in the mode of secondary electrons (SE) emitted from the surface layer with a thickness of less than 5 nm [21]. ...
... The SEM method was used to record microscopic images in the mode of secondary electrons (SE) emitted from the surface layer with a thickness of less than 5 nm [21]. The EDS method was used to record X-ray quanta of characteristic X-radiation with an energy of ≤10 keV generated in subsurface layers with thicknesses of up to 1 μm [21,22]. For the alloy used in this work, the depth of EDS analysis at E 0 = 20 keV was evaluated at 490 nm [18]. ...
The local chemical composition of the most characteristic regions of a rough etched layer on the front side of the Pt–Pd–Rh–Ru gauze with a composition of 81, 15, 3.5, 0.5 wt %, respectively, after the oxidation of NH3 with air at Т = 1133 K and a pressure of 3.6 bar was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The local chemical composition of the grain surface in the low etching region, on porous crystal agglomerates (cauliflowers) in the etched layer, and between cauliflowers at the bottom of pore voids was determined. Pt, Pd, Rh, Ru, C, O, and N were recorded on grains, cauliflowers, and pore bottom, which had different defect concentrations and temperatures. The metal contents on the grains and at the bottom of pore voids coincided with the composition given by the gauze manufacturer, whereas cauliflowers had a higher Rh content (12.6 at %). Reliable quantitative data on the contents of Oab and Nab atoms in the subsurface layers of grains, cauliflowers, and pore bottom were obtained for the first time: 18.6, 7.3, and 10.4 at % for Оab and 17.1, 16.8, and 33.6 at % for Nab, respectively. The maximum content of Oab atoms (18.6 at %) was recorded in defect regions with low temperature (grains in the low etching region), while increased content of Nab atoms (33.6 at %) was found in regions with low defect concentrations but elevated temperature (pore voids). These data on the Oab and Nab contents in regions with different degrees of defectiveness and temperatures made it possible to reveal for the first time the types of defects on which predominantly the O and N atoms penetrate into the catalyst during NH3 oxidation. The Oab and Nab atoms accumulate in the subsurface layers of the Pt–Pd–Rh–Ru metal alloy during intercalation of O atoms on the grain boundaries and in etch pits and penetration of N atoms into the lattice of the alloy. The reported dissolution model of O and N atoms in the subsurface region of the catalyst will provide deeper understanding of the mechanism of NH3 oxidation that forms NO oxide and of the related etching process.
... To avoid this problem we recall the Rutherford backscattering technique of condensed matter physics [18]. We consider the elastic scattering of a particle in the beam with mass m b and a stationary particle of mass m t located in the sample. ...
... The large coupling constant and mass of the monopoles single out this particle with respect to the abundant conventional particles that might surround them. An intelligent use of ion beams in parasitic experiments might lead to the detection of monopoles by eliminating the conventional background by borrowing a technique that condensed matter physicists use to detect impurities [18]. Beam particles, protons or ions, can scatter from monopole-antimonopole pairs or monopolium produced in colliders leading to a well defined scattering pattern which can be detected by small implementations in ongoing experiments. ...
Magnetic monopoles have been a subject of interest since Dirac established the relationship between the existence of monopoles and charge quantization. The Dirac quantization condition bestows the monopole with a huge magnetic charge. The aim of this study was to determine whether this huge magnetic charge allows monopoles to be detected by the scattering of charged ions and protons on matter where they might be bound. We also analyze if this charge favors monopolium (monopole–antimonopole) annihilation into many photons over two photon decays.
... However, an additional complication is that the filling of the K shell leaves another higher shell vacancy, and subsequent cascade of atomic electron transitions results in some being ejected from the atom as Auger electrons (typically within 10 --13 --10 --15 s [66]). The latter have significant momentum which has to be included in the mass reconstruction (Fig 3.5b). ...
Sterile neutrinos in the keV mass range may constitute the galactic dark matter. Various proposed direct detection and laboratory searches are reviewed. The most promising method in the near future is complete energy-momentum reconstruction of individual beta-decay or K-capture events, using atoms suspended in a magneto-optical trap. A survey of suitable isotopes is presented, together with the measurement precision required in a typical experimental configuration. It is concluded that among the most promising are the K-capture isotopes 131Cs, which requires measurement of an X-ray and several Auger electrons in addition to the atomic recoil, and 7Be which has only a single decay product but needs development work to achieve a trapped source. A number of background effects are discussed. It is concluded that sterile neutrinos with masses down to the 5-10 keV region would be detectable, together with relative couplings down to the level 10-10-10-11 in a 1-2 year running time.
... A thickness of only 200 nm is sufficient for decelerating Au and I ions with an energy of 200 keV, compared to B and N ions with the same ion acceleration energy studied in the past report, which require 1200 and 1000 nm of NaCl as sacrificial layers [22]. The difference is explained by the stopping power of the target materials against incident ions [27][28][29][30] The absolute value of the exact number of ions that arrive at the sample in the actual experiment of ion beam irradiation was unknown in a previous study although the number of ions is mandatory information for the discussion to comprehensively investigate the effects of the introduced ions. ...
Graphene is a promising material in its isolated form for applications to next-generation electronic devices; however, a strategy for modifying graphene to tune its carrier transport properties is required to meet the various requirements related to carrier density, electric mobility, and spin-orbit coupling. In this study, we modify graphene by irradiating the Au/I ion beam at 200 keV with doses of 10¹³–10¹⁴ cm⁻² using a NaCl sacrificial layer to introduce ions as guest chemical species into a two-dimensional graphene sheet as a quantitative chemical modification method. Ion-irradiated graphene was evaluated by Raman spectroscopy, electrical conductivity measurement, and Rutherford backscattering spectrometry after removing the sacrificial layer. Both vacancies of carbon atoms, and Au atoms of 2.1 × 10¹³ cm⁻²/I atoms of 1.2 × 10¹³ cm⁻² are introduced into graphene by irradiating an ion beam at a dose of 10¹⁴ cm⁻²; the latter acts as charged impurities, which results in the Raman D’ band and the downshift of the Fermi energy through hole carrier doping. The clarified knowledge of influences on electron transport properties by heavy-ion beam irradiation of graphene will help lead a new class of material development for electronics and spintronics.
... Consequently, we see that the spontaneous K-shell emission rate is proportional to Z 4 107 . It can be shown that for atoms the Meitner-Auger yield W A is almost independent of the effective nuclear charge 108 . A semi-empirical expression for the X-ray yield is introduced in Ref. 109 : ...
We develop a self-consistent Maxwell-Bloch formalism for the interaction of X-rays with two-dimensional crystalline materials by incorporating the Bloch theorem and Coulomb many-body interaction. This formalism is illustrated for graphene, by calculating the polarization-dependent XANES, formulating expressions for the radiative and Meinter-Auger recombination of core-holes, and the discussion of microscopic insights into the spectral oscillations of EXAFS beyond point scattering theory. In particular, the correct inclusion of lattice periodicity in our evaluation allows us to assign so far uninterpreted spectral features in the Fourier transformed EXAFS spectrum.
... When a projectile particle moves through matter at velocities greater than the mean orbital velocity (Bohr velocity) of atomic or molecular electrons in a shell or subshell of a given target atom, the charge state of the projectile particle increases. Eventually, the projectile particle becomes fully ionized [30,31]. In the pores of nanotubes, the interaction of a projectile particle with the target atoms on the wall inside the pores is less frequent compared to the situation when the projectile particle channels through a crystalline solid such as single crystal silicon. ...
Ion channeling refers to the guided movement of high energy ions through axial/inter-planar regions in single crystals and ordered nanostructures under the influence of the Coulomb scattering process. The process...
... EDS measurements (data not shown) were also made at several different locations including one at different electron beam energy and no Xe was detectable. In addition to electron beam generated Bremsstrahlung radiation backgrounds that set a lower bound in detection sensitivity, the detection of Xe in the sample with a higher-Z element Hf could be further limited by matrix dependent effects, such as attenuation of Xe x-rays in hafnia and pulse pileups of strong matrix signals [37]. The ∼1.8% of entrapped Xe estimated from RBS may be an upper bound and the actual Xe concentration in the film could be lower, as will be discussed later when EELS results are presented. ...
Laser damage-prone precursors in high index materials such as hafnia are believed to be the primary limiter in the performance of dielectric multilayer films to advance ultra-high power and energy laser applications. Removing or suppressing these precursors is the key to fabricating laser damage resistant thin films for the enabling technologies. Early work has revealed that nanobubbles formed by entrapped argon (Ar) working gas in ion beam sputtering (IBS) produced hafnia films are primarily responsible for the onset of laser damage upon exposure to UV, ns-laser pulses. In this study, we demonstrate that the UV ns-laser damage onset of IBS produced hafnia films can be improved to 3.1 +/- 0.2 J/cm² by substituting the conventional Ar working gas with xenon (Xe), a nearly 1 J/cm² increase from that of the Ar produced hafnia films. In addition to the suppression of the overall point-defect density of the hafnia films, the reduction of the Xe entrapment eliminates the nanobubbles and the generation of plasmas that initiates the laser damage. The defect suppression and its correlation to the increase in laser damage threshold is revealed by the combined analysis of Rutherford backscattering spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, and laser damage testing. Monte Carlo simulations suggest a much smaller entrapment of Xe gas by comparison to Ar, which is attributed to the significant difference in the energy of the reflected neutrals (3X) which are likely to be implanted. These results provide an effective process route with a fundamental understanding for producing high laser damage resistant dielectric films for high power and high energy laser applications.
... target like gold [89], keeping the whole scattering chamber electrically isolated for using it as a Faraday cup [90], using two Faraday cups one in front of the target and another behind the target [91]. Target thickness, as well as target contamination, can be correctly measured with Rutherford back-scattering technique [92]. ...
Experimentally, x-ray production cross-sections are measured, but ionization cross-sections are calculated theoretically. The uncertainty of the measured L x-ray production cross-section is mainly statistics and detector-efficiency driven. But the experimental ionization cross-section involves many other factors because the relationship between the production and ionization cross section involves various atomic parameters and thus its uncertainty equation is complex. Consequently, determining the measurement uncertainty in L subshell ionization cross-section is always difficult. We have studied this issue in the simplest way, where the rule of weighted propagation of relative uncertainty is utilised. We notice that larger uncertainties are involved in atomic parameters relevant to L1 (2s1/2) subshell than those associated with the other two L2 (2p1/2) and L3 (2p3/2) subshells. Hence, comparison between theory and experiment would give higher emphasis on L2 and L3 subshell ionization cross sections. We believe this work makes us aware that the appropriate uncertainty evaluation is extremely important for providing the right judgment on the data.
... Micrographs of the surface of the layers were taken on an MII-4 microscope [7]. ...
... Micrographs of the surface of the layers were taken on an MII-4 microscope [7]. ...
... Rutherford backscattering spectrometry (RBS) is known to be one of the techniques ideal for analysis of thin films (Chu et al. 1978;Feldman and Mayer 1986;Tesmer et al. 1995;Bird and Williams 1989;). Very similar to Rutherford's gold foil experiment, RBS sample analysis is typically achieved by exposing samples to high energy helium ions ( 4 He + ) from a particle accelerator and measuring the elastically backscattered ions with an energy sensitive detector. ...
This manuscript outlines current research activities based on ion beam science at GNS Science in New Zealand. Ion beam analysis methods include Rutherford backscattering and nuclear reaction analysis which trace back to Rutherford's famous ‘gold foil’ and ‘splitting the atom’ experiments. These ion beam-based methods generally offer the ability to analyse materials for every element of the periodic table, to ppm concentrations, and with depth profiles ranging from a few nm to several microns. Ion beam methods are now also used to modify and create new materials precisely. Rutherford’s early research now has a legacy at GNS Science’s Materials team to discover, design, and develop materials for energy efficient modern applications for a low carbon future. These include magnetic sensors for security products, nanostructured magnetic materials for energy conversion, thermoelectric devices for energy harvesting, and catalytic development for clean energy carriers and energy efficient communication devices.
... The preparation of sample is an important part of microscopy and there are many techniques (and variations) that can be used. The most generally used methods for final thinning includes ion milling, reactive ion technique, chemical polishing, electro polishing, etc. [8]. Materials which have dimensions short enough to become electron transparent like as powders that can be quickly produced through the dilute sample deposition containing the specimen upon support film or grids. ...
The most abundant organisms in our biosphere are bacteria as Escherichia coli. Slight climate changes can potentially be disastrous to the life processes of bacteria; this can result in the prolific advantage for the production of nanoparticles. On the other hand synthesis of metal nanoparticles by eukaryotic cells such as fungi Aspergillus niger is reported. A. niger have the advantage of producing very high yields of secreted proteins, which may increase nanoparticle synthesis rate. Mycelia provide a much higher surface area than bacteria and this area could be used to support the interaction of metal ions and fungal reducing agent thus enhancing the reduction of metal nanoparticles. The bio reduction of NPs was monitored by ultraviolet-visible spectroscopy, and the nanoparticles obtained were characterized by electron microscopy. In bacterial culture ZnO and Pb(NO3)2 NPs have sharp absorbance with the highest peak at 300nm and 250nm respectively. On the other hand, in fungal culture ZnO and Pb(NO3)2 NPs have highest absorbance peak at 230nm and 240nm respectively. The synthesized NPs (fungal biomass) were almost spherical in shape and some of them were aggregated ranging in size from 30-70nm and 10-50nm stabilized in the solution. Furthermore, the antimicrobial potential of zinc and lead nanoparticles was systematically evaluated. The synthesized nanoparticles could efficiently inhibit various pathogenic organisms, P. aeruginosa and S. aureus. The bactericidal effect of zinc and lead nanoparticles were compared based on diameter of inhibition zone in agar diffusion assay, disc method tests and minimum inhibitory concentration (MIC).
... Of course, the energy spectrum of an electron gas formed by high-energy electron irradiation can differ significantly from the one formed during the dielectric breakdown, but this is a second-order effect. The characteristic hot electron thermal relaxation length in a solid is about 3 nm [15]. This means that the heat generation region is actually determined by an electron beam diameter. ...
The phase transformations of stoichiometric HfO2 and non-stoichiometric HfOx oxides grown by ion-beam sputtering-deposition during their electron beam crystallization were investigated. It was found that the sequences of crystalline phase formations in stoichiometric and non-stoichiometric oxides are significantly different. An amorphous HfO2 film crystallizes first to form monoclinic α-HfO2 phase nanocrystals and then tetragonal β-HfO2 phase nanocrystals. In non-stoichiometric HfOx oxides (x = 1.82), in contrast to HfO2 oxides, hexagonal α-Hf phase metal clusters were initially present. During the crystallization process, the metallic α-Hf phase growth was observed first with the simultaneous appearance of the monoclinic α-HfO2 phase. Then the orthorhombic-I γ-HfO2 phase appeared, while the α-Hf phase growth ceased. The composition of the investigated non-stoichiometric HfOx oxides was chosen to be the same as in the dielectric layer of resistive memory cells (ReRAM). The crystallization of oxides was carried out in a local region, the sizes of which are comparable with the size of the ReRAM filament. This made it possible to partially project the crystallization results onto the forming and switching processes in ReRAM cells.
... X-rays can have higher absorption due to the photoelectric effect, Compton and pair production, which cross-section depends on the effective atomic number Z eff raised to Z eff 4−5 , Z eff , and Z eff 2 , respectively (29). Electronic and ionic stopping powers increase with the Z eff by the presence of the heavy Au-NPs (30). The gold was taken in consideration with respect to other heavy elements for its high biocompatibility, stability, low reactivity, and simple elimination (31). ...
2.0 MeV proton beam accelerated at Tandetron is extracted in air through a thin film and allowed to scatter to irradiate the cell culture attached to the polymeric base of a biological flask. The irradiated cells were human medulloblastoma cell line Daoy treated with and without 5 nm sized spherical gold nanoparticles. Proton doses from 0.5 to 1.5 Gy have been employed to irradiate the cultures and to investigate the role of the radiotherapy performed with and without the use of the gold nanoparticles. Results indicated that cell survival is significantly reduced to about 50% when the nanoparticles at a concentration of about 6 × 10¹³ particles/ml are employed.
... Notably, the molecular stoichiometry is not retained in the RBS data because elements of low atomic weight are likely to escape due to the high-energy ion irradiation 60 . In our film ruthenium is the heaviest element and, because momentum transfer from incident He + is inefficient, we take the ruthenium count as a reliable measure of the deposited molecular density (each molecule contains one ruthenium atom, so the ruthenium count represents the molecular density). ...
Electronic symmetry breaking by charge disproportionation results in multifaceted changes in the electronic, magnetic and optical properties of a material, triggering ferroelectricity, metal/insulator transition and colossal magnetoresistance. Yet, charge disproportionation lacks technological relevance because it occurs only under specific physical conditions of high or low temperature or high pressure. Here we demonstrate a voltage-triggered charge disproportionation in thin molecular films of a metal–organic complex occurring in ambient conditions. This provides a technologically relevant molecular route for simultaneous realization of a ternary memristor and a binary memcapacitor, scalable down to a device area of 60 nm². Supported by mathematical modelling, our results establish that multiple memristive states can be functionally non-volatile, yet discrete—a combination perceived as theoretically prohibited. Our device could be used as a binary or ternary memristor, a binary memcapacitor or both concomitantly, and unlike the existing ‘continuous state’ memristors, its discrete states are optimal for high-density, ultra-low-energy digital computing.
... Following the Auger cascade, the atoms remain strongly positively charged. They may capture electrons from surrounding water molecules and induce strong perturbation in the close environment [Feldman and Mayer, 1986]. ...
About 50% of the cancer patients who are treated benefit from radiation therapy. Conventional radiotherapy consists of high energy X-rays traveling through the tissues, so that deeply sited tumors are treated in a non-invasive way. Unfortunately, X-rays are not tumor selective and healthy tissues may be damaged. This lack of selectivity is responsible for severe side effects and/or secondary cancers. Hence, improving the differential of radiation effects between the tumor and surrounding tissues remains a major challenge. Particle therapy (treatment by protons or carbon ion beams) is considered as one of the most promising technique because, by opposition to X-rays, the energy deposition of ions is maximum at the end of their tracks. When the beam is tuned so that the maximum reaches the tumor, there is no damage induced in tissues siting after the tumor. Another important added value is that heavy ions are more efficient to treat radioresistant tumors. The use of this modality is however restricted by the low but significant damage that is induced to normal tissues located at the entrance of the track prior to reaching the tumor. To improve the performance of particle therapy, a new strategy based on the combination of high-Z nanoparticles with ion beam radiation has been developed by the group at ISMO. This approach aims at using nano-agents not only to increase radiation effects in the tumor but also to improve medical imaging with the same agent (theranostic). Nanoparticles present a remarkable surface chemistry, which allows functionalization with ligands able to improve biocompatibility, stability as well as blood circulation and accumulation in tumors. The group already demonstrated the efficiency of small (≈ 3 nm) gold and platinum nanoparticles to amplify the effects of medical carbon ions in normoxic conditions (in the presence of oxygen). However, radioresistant tumors may host hypoxic regions. It is thus urgent to quantify and characterize the influence of oxygen on the radio-enhancement effect. The goal of my thesis was to study the influence of oxygen on medical ion radiation effects in the presence of gold and platinum nanoparticles. This was performed using two radioresistant human cancer cell lines: HeLa (uterine cervix) and BxPC-3 (pancreas). Different radiation modalities were used: carbon and helium ion beams delivered by a passive scattering delivery system and carbon ion beams delivered by a pencil beam scanning system. The major results of this work are the following. In oxic conditions (O₂ concentration = 20%), an enhancement of ion radiation effects was observed for the two nanoparticles (at the same concentration in metal). This effect decreased with the oxygen concentration but remained significant for a concentration of 0.5%. No significant difference was found between the cell lines. Interestingly, the oxygen-dependence varied with the type of radiation. An attempt to explain the effect of oxygen by molecular processes is proposed. Perspectives of further developments are suggested.
... The methods of SEM and EDX have different effective depth of analysis [24,25], because they are based on the detection of radiation emitted from nearsurface layers of different thicknesses. SEM creates images generated by secondary electron (SE) and backscattered electrons (BSE). ...
Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to study microstructure, morphology and chemical composition of the surface and near-surface layers of polycrystalline wire of commercial platinoid gauzes containing Pt (81 wt %), Pd (15 wt %), Rh (3.5 wt %), and Ru (0.5 wt %) after ammonia oxidation (10 vol % NH3) by air at 1133 K for 50 h in the presence of these gauzes. Upon the completion of the catalytic reaction of ammonia oxidation, reconstruction (catalytic etching) of the surface layer on the backside of gauze wire (in the direction of the gas flow) was observed, in which the regions with different degrees of etching were identified. The analysis of these regions showed that the catalytic etching of the platinoid wire is initiated by etching the surface layer in the region of grain boundaries and dislocations in the course of highly exothermic catalytic reaction of ammonia oxidation by oxygen penetrated in the regions of defects. The regions with minimal etching contain smooth grains with crystalline terraces, 50 nm high, and with etching pits with size of ~72 nm in a concentration of 4.2 × 10⁸ cm–2. The region with medium etching includes rough grains with etching pits with size of ~85 nm in a concentration of 2.5 × 10⁸ cm–2. The regions with maximal etching consist of recrystallized grains with large pores with sizes of 350–400 nm in concentration of 8.9 × 10⁶ cm–2. These grains are separated by voids with a width of 1–5 μm and a depth of 10 μm, which increases the specific surface area in the surface layer of wire. The growth of the specific surface area of the platinoid wire is accompanied by an increase in the volume rate of ammonia oxidation and, as a result, local overheating due to the high exothermicity of the reaction. With increasing temperature, the rate of diffusion of metal atoms increases, which, in turn, accelerates etching in this region. These processes lead to increasing the region of etching along the wire, which points to the autocatalytic regime of etching of platinoid gauzes in ammonia oxidation by oxygen.
... The Auger effect especially concerns low-Z atoms [99] and therefore would not be a major contributor to 5. Influence of nanoparticles design on the radiosensitization the dose deposited in the presence of high-Z NPs. Indeed, it is dominant for Z < 15 but almost equal to 0 for Z > 60 [100]. ...
Les travaux présentés dans le cadre de cette thèse sont divisés en trois grandes parties qui concernent l'utilisation des nanoparticules métalliques pour augmenter les effets de la radiothérapie. Cette utilisation très particulière des nanoparticules n'a fait l'objet, jusqu'à présent, que d'études précliniques sauf un nano-objet qui fait actuellement l'objet de phases cliniques I et II à l'Institut Gustave Roussy de Villejuif, France. La première partie est une recherche bibliographique qui s'est concrétisée par la parution d'un état de l'art dans une revue internationale. Ce dernier identifie les paramètres jouant un rôle clef dans l'augmentation de la radiothérapie par les nanoparticules. Suite à cette étude de la littérature, le constat a été fait que la recherche préclinique en nanomédecine est plus longue et plus onéreuse que celle qui s'intéresse aux objets (macro-molécules) de taille standard. C'est pour améliorer cette prise en charge préclinique qu'une plate-forme informatique de simulation Monte-Carlo des interactions nanoparticules à rayons X a été développée. Cette dernière ayant pour objectif de réaliser un classement in silico rapide et fiable des nanoparticules radio-sensibilisantes permettant d'identifier de façon efficiente les nanostructures présentant les propriétés les plus prometteuses. La seconde partie de cette thèse consiste en une analyse de robustesse de ce simulateur, visant à identifier les paramètres de variabilité intrinsèques au simulateur et à quantifier leur influence sur la variation des résultats. Trois paramètres ont été identifiés comme paramètres critiques de simulation et doivent être maintenus constants entre les différentes études. Enfin, une troisième partie traite de l'application de cet outil de simulation au screening virtuel de nanoparticules radiosensibilisantes. Dans cette partie sont réalisées une analyse de prédiction in silico / in vitro et une analyse de prédiction in silico / in cellulo. Les résultats très encourageants (correspondance acceptable entre les prédictions du simulateur et les résultats in cellulo) obtenus durant cette dernière phase ont également fait l'objet d'une soumission à publication dans une revue internationale.
... (a) Schematic of an RBS experiment, (b) an illustration of the backscattering process, and (c) an illustration of the electronic stopping process, which takes place both during the inward path of the He + ion.Figure (a)and (b) are adapted from[143]. ...
The unparalleled technological maturity of silicon (Si) can be exploited to develop CMOS-compatible optoelectronics such as photodetectors and imaging arrays. However, the low-attenuation wavelengths commonly used in fibre-optics (up to 1650 nm) fall below the 1.12 eV band gap of Si (efficient absorption only occurs at wavelengths less than 1100 nm), thus requiring the realisation of sub-band gap photoresponse. A promising method to achieve this is to add an intermediate band within the band gap by incorporating appropriate impurities into the Si lattice at high concentrations (often beyond the thermodynamic solubility limit), or hyperdoping. Indeed, Au-hyperdoped Si made by ion implantation and pulsed laser melting (PLM) has been shown to exhibit strong sub-band gap optical absorption in the near-infrared and has led to the demonstration of a Si-based near-IR photodetector. The Au sub-band gap absorption has been shown to increase with the Au dose, and significant room for further improvement of the device performance has been predicted. While these results illustrate the potential of hyperdoped Si for photodetection in the near-infrared, the material properties of Au- and other transition-metal-hyperdoped Si remain elusive. With this as a premise, this PhD work has focused on characterising and understanding the properties of Au-hyperdoped Si. In this thesis, detailed Rutherford backscattering spectrometry and channeling measurements are undertaken to examine the lattice position of the Au atoms. It is shown that the Au occupies mostly substitutional lattice positions within the hyperdoped Si lattice. In addition, by varying the iplant energy and the implanted Au dose, thicker layers of Au-hyperdoped Si with higher Au concentrations are demonstrated. However, although the Au atoms remain significantly substitutional (more than 50% substitutional in most cases) at high Au concentrations, the Au distribution is found to be non-uniform. Further structural characterisation by transmission electron microscopy and energy dispersive spectroscopy reveals a new observation where filaments of single crystalline, Au-rich Si regions emerge after PLM. The local concentration within such filaments is estimated to be at least 3 at. %, and the proximate Si lattice is found to be slightly skewed. These features suggest a novel segregation regime in Au-hyperdoped Si that is distinctly different to conventional 'cellular breakdown' in hyperdoped Si, in which impurity precipitation might be observed at cell-walls. In spite of the inhomogeneous behaviour of Au-hyperdoped Si at high Au concentrations, the sub-band gap optical absorption is found to continue to increase with increasing substitutional Au dose. This is consistent with density functional theory calculations in which the isolated substitutional Au configuration is found to give rise to significant sub-band gap optical absorption. This enhancement in sub-band gap optical absorption is found to deactivate after subsequent thermal annealing. We show that this behaviour can be correlated with a loss of Au substitutionality. Furthermore, the detailed atomistic mechanism for the thermal relaxation of Au-hyperdoped Si is investigated by correlating the experimental observations with density functional theory results. We show that the thermal relaxation of Au-hyperdoped Si is a multi-step process which involves (1) the exchange of substitutional Au with interstitial Au, (2) the trapping of Au to local sinks, (3) the formation of Au dimers, and (4) the clustering and nucleation of Au precipitates. Furthermore, the activation energy associated with loss of Au substitutionality is found to be 1.6 eV, a similar value to the diffusion of Au in defective Si. In the final chapter of this work, experimental evidence for a vacancy trapping model is presented. We propose that vacancies are introduced during the resolidification process to minimise local strain around Au-rich regions. Furthermore, the trapped vacancies are shown to be decorated with Au after subsequent thermal annealing. We show that such a behaviour is not limited to Au-hyperdoped Si and may be a universal phenomenon that occurs during the incorporation of large size impurities into Si as the Si is rapidly resolidified from a laser-induced melt.
... detection angle, at the CEDAD Laboratory of Brindisi (Italy) [9]. ...
... detection angle, at the CEDAD Laboratory of Brindisi (Italy) [9]. ...
Energy loss, dispersion (energy loss straggling) and asymmetry (skewness and kurtosis) of energy loss distribution curves of Li, C and O ions in varying thicknesses of terbium foils were measured. The measurements were performed, through transmission technique, by utilizing 15UD Pelletron accelerator at Inter-University Accelerator Centre (IUAC), New Delhi, India. These measured energy loss and straggling values were compared with the corresponding computed values adopting the most commonly used theoretical/semiempirical formulations. The purpose of this comparison was to identify the best theoretical formulation for the considered combinations. Benton and Henke formulation-based computed values showed better agreement with the measured energy loss values. Concerning energy loss straggling, Titeica theory’s predicted values were found to be better. Asymmetric parameters (skewness and kurtosis) reveal that the shape of energy loss distributions of considered ions in terbium foils was mesokurtic-type Gaussian. The precise knowledge of these parameters is crucial for understanding energy loss distribution for considered ion-matter combinations. Further, these could be used as input in various computer codes (SIMNRA, RUMP and NDF) to simulate spectra obtained through different ion beam-based techniques.
In order to promote the application of TiO2 in surface modification technologies, a detailed understanding of its structure and properties is necessary. For this reason, the reactivity and corresponding surface chemistry of stoichiometric and non-stoichiometric single crystals of titanium dioxide have been widely studied. In Part II of this review, special attention is paid to the role of individual surface sites and the effect of available charge on the adsorption processes on stoichiometric and reduced single crystal rutile and anatase surfaces. In addition, the most appropriate surface science methods used to study the surface chemistry of these surfaces are also highlighted. An understanding of the interaction of H2O and O2 with oxide surfaces is extremely important because these adsorbates form a de facto part of the environment in all technological applications. Moreover, they play an extraordinarily important role in the processes taking place in high-performance devices in the fields of energy, environment, and health. Consequently, special consideration is given to the adsorption and dissociation processes of the most technologically important inorganic adsorbates, such as H2O and O2, on model low Miller index single crystal surfaces of titania. In addition, light-induced reactivity of TiO2 and its application is also considered. Furthermore, the engineering of TiO2 nanocrystals with well-defined facets, their unusual photocatalytic properties, and applications are also briefly considered.
This chapter gives a brief overview of methods used to analyze functionalized surfaces with a comparison among different working principles and performances. The schematic, yet nonexhaustive summary, can guide a nonexpert reader in evaluating potential and limitations of some of the most used analytical tools. Most significant methods such as electron and X‐ray spectroscopy, secondary ion mass spectrometry, and vibrational spectroscopy (Raman and Infrared) are in focus. These techniques will be described in general terms, to provide a concise overview of their working principles, capabilities, and applications. The second part of this chapter will present exciting examples in which ceramic nanostructures are exploited to enhance the chemical sensitivity in optical sensing, vibrational spectroscopy (IR and Raman), and mass spectrometry and enable novel surface analytical tools based on their versatile properties.
Carbon is one of the unique elements that ever exist, which can be in a variety of forms. The so‐called carbon allotropes exhibit widely different properties. Novel carbon nanostructures (CNS), such as carbon nanotubes and graphene, are becoming at the forefront of material research as a major nanotechnology component. This chapter briefly discusses the recent development of carbon allotropes and their typical fabrication and characterization methods. Chemical vapor deposition (CVD) has been established as a very popular method for CNS fabrication. In this prospect, the CNS nucleation and growth mechanism on a catalyst or substrate, as well as experimental parameters, play a fundamental role in controlling the forms of nanostructures, carbon hybridization, and growth of yield. On the other hand, the ion irradiation technique has been proven as an effective method for surface modification to produce CNS, such as ripple and nanofibers, with good control of growth without any catalysts at ambient temperature. Raman spectroscopy and electron microscopy offer a fast evaluation of the quality of CNS growth. Furthermore, their structure and properties evolution can be visualized in detail through in situ transmission electron microscopy techniques. The overview will focus on the most representative carbon allotropes, i.e. graphene and carbon nanotubes, but other carbon family members are also remarked on.
TiO2 is an important material for reasons that are related to fundamental research, as well as to existing and potential technological applications. There is no aspect of the chemistry and physics of TiO2, which is not decisively affected by the presence of defects. An increase in the present state of understanding of the science of TiO2-based material interfaces is essential for progress in this area; such progress is possible thanks to high purity TiO2 single crystals which are ideal for basic investigation of and on titanium dioxide surfaces under carefully controlled laboratory conditions. Surface functionalization through precise control of the nature of the defects, their concentration and arrangement, allows the modification and optimization of the material, or even the generation of completely new targeted properties of the surfaces independent from the bulk. A new generation of TiO2 surfaces with enhanced functionality and performance limits has been successfully created by the use of surface engineering. In Part I of this review, a brief description of the results is given of the experimental and theoretical investigations on the influence of the defect states on the correlation between crystallographic, electronic and atomic geometrical structures of the most technically important single low Miller index titania surfaces and their physical properties. In addition, the formation and detection techniques for surface oxygen vacancies are also considered. Special attention in this area is given to the behaviour of the electrons remaining in the system upon vacancy formation and the ability of current quantum-mechanical modelling methods to provide a precise description of the electronic structure of non-stoichiometric TiO2. These fundamental studies allow scientists to create real functional TiO2 surfaces, such as the targeted nanostructured thin films with predefined structure and properties required for the development of high-performance devices in the fields of energy, environment and health.
Interactions between elementary excitations such as plasmon-exciton and plasmon-phonon are of great interest from a fundamental point of view and for novel applications. While plasmon-exciton have been extensively studied both experimentally and theoretically, the interaction mechanisms between acoustic vibrations (phonons) and localized surface plasmons (LSPs) remain quite unexplored. Here we present a theoretical investigation of the interactions between confined acoustic vibrations and LSPs involved in resonant acoustic phonon Raman scattering. We express the Raman scattering process in the framework of the Fermi's golden rule and introduce for the first time the concept of Raman energy density (RED). Similarly to the Raman-Brillouin electronic density (RBED) introduced for semiconductors, this new physical quantity is used as a theoretical tool for the interpretation of resonant Raman scattering mediated by LSPs in metallic nanoparticles. The RED represents the electromagnetic energy density excited by the Raman probe and modulated by the acoustic vibrations of the nanoparticle. We show that, similarly to the local density of optical states (LDOS) and the RBED, the RED can be mapped in the near-field region, which provides a clear picture of the interaction between LSPs and acoustic vibrations giving rise to inelastic scattering measurable in the far-field. Here, we use the newly introduced RED concept to investigate elastic (an)isotropy effects and calculate the Raman selection rules of spherical nanoparticles embedded in a dielectric environment.
The effect of lithium on the structural-phase state of aerospace aluminum alloy 1421 of the Al–Mg–Li system prepared by rapid solidification is studied. Analysis of the composition of the surface layers of alloy samples carried out by means of nuclear reaction analysis establishes that lithium diffuses to the surface at elevated treatment temperatures and its concentration in a thin surface layer (0.1 μm) reaches 38 at %, which is 4.8 times higher than the calculated Li content in the alloy. By measuring the microhardness, strengthening of the samples is determined upon isothermal annealing at a temperature of 400°C, which is caused by the precipitation of metastable lithium-containing phases. The results of X-ray diffraction analysis indicate an increase in the fraction of Li2O2 peroxide on the foil surface upon annealing.
This article reports experimental data on a double-step technology for processing a model organic contaminant (m-cresol) adsorbed in the pores of an iron-containing carbon adsorbent (specific surface area 616 m²/g) under microwave irradiation. The first step comprised the decomposition of cresol into a hydrogen-containing gas and a carbon residue under plasma-catalytic conditions assisted by microwave irradiation at an induced temperature of 600°C. Cresol was completely converted after 25 min of the MW irradiation. The second step consisted of adsorbent regeneration (by CO2 treatment under MW irradiation to remove the carbon residue) followed by thermal shock treatment (by decomposition of a pre-adsorbed ammonium hydroxide). After the regeneration, the specific surface area was 500 m²/g. The regenerated adsorbent exhibited almost the same cresol adsorption capacity as the starting material.
Many studies have already been performed on the thermal annealing of fresh and aged swift heavy ion-irradiated polymers in a vacuum. In this paper we examine the influence of different environments on annealing behaviour. The basic tool for this study is current/voltage spectroscopy with the alternating voltage applied across the etched tracks. In previous work of this series it was shown for etching of previously annealed aged swift heavy ion-irradiated polyethylene terephthalate foils in dry air that at ∼ 50°C, a dip overlapped the expected Arrhenius correlation in the Arrhenius plot of the etchant breakthrough times. We had attributed that dip tentatively to the etching of the swift heavy ion track core material, as the latter had been subjected to extremely high radiation-damage and thus differs strongly in its composition from pristine bulk material. Repetition of this experiment under different annealing environments enables us to draw conclusions about the competition between the different polymeric disintegration and healing mechanisms in swift heavy ion tracks. These results should be useful for better estimation of the polymeric durability in different environments. First tests with polyimide reveals that a similar dip structure also shows up here, indicating that this finding may be a general effect for annealing of ion-irradiated polymers.
The monograph describes the scientific foundations of nuclear-physical diagnostics of energy input by Intense Pulsed Ion Beams as applied to their main technological applications. The diagnostics is mostly based on instantaneous products of interaction of ions with materials, including ablation of surface layers, Rutherford Backscattering of ions, characteristic X-ray, gamma and neutron radiation, while delayed measurement of induced radioactivity, ion analysis methods for depth and surface, analysis of tracks and color changes of irradiated near-surface layers are used for calibration of the prompt techniques. The considered techniques have been tested for accelerators using ion diodes of different types, with special emphasis on the collective acceleration of ions in the Luce diode. The monograph is intended for specialists in the field of high-current electronics, generation of pulsed beams of charged particles and experimental nuclear physics and can be used as a textbook for students and postgraduates of physical specialties.
The effect of helical rolling at 1000°C of the Ti-6Al-4V alloy on the change in the spectra of elastically and discretely scattered electrons is investigated. The differences in the spectra of elastically and discretely scattered electrons are revealed in comparison with the initial state of the Ti-6Al-4V alloy. For the first time, the dependences of the changes in the energy and intensities of the spectra of elastically and discretely scattered electrons on the emission angle from the alloy surface were recorded. The changes in the energy and shape of the spectra are the result of changes in the crystal structure of the alloy associated with the deformation. The deformation leads to a change in the parameters of the crystal lattice, a rearrangement of the position of atoms and a change in the energy structure of the upper electron shells of atoms. This, in turn, changes the magnitude of the energy loss of primary electrons to excite plasmons.
X‐rays and forward ion emission from laser‐generated plasma in the Target Normal Sheath Acceleration regime of different targets with 10‐μm thickness, irradiated at Prague Asterix Laser System (PALS) laboratory at about 1016 W/cm2 intensity, employing a 1,315 nm‐wavelength laser with a 300‐ps pulse duration, are investigated. The photon and ion emissions were mainly measured using Silicon Carbide (SiC) detectors in time‐of‐flight configuration and X‐ray streak camera imaging. The results show that the maximum proton acceleration value and the X‐ray emission yield growth are proportional to the atomic number of the irradiated targets. The X‐ray emission is not isotropic, with energies increasing from 1 keV for light atomic targets to about 2.5 keV for heavy atomic targets. The laser focal position significantly influences the X‐ray emission from light and heavy irradiated targets, indicating the possible induction of self‐focusing effects when the laser beam is focalized in front of the light target surface and of electron density enhancement for focalization inside the target.
Low‐energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well‐defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF2 as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF2 is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF2 can be used as reference, its atomic surface concentrations have to be determined. Here, 3‐keV He+ scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. High‐purity CaF2 is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF2 (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu.
Electron probe microanalyser measurements of trace elements with high accuracy are challenging. Accurate Al measurements in olivine are required to calibrate SIMS implant reference materials for measurement of Al in the solar wind. We adopt a combined EPMA/SIMS approach that is useful for producing SIMS reference materials as well as for EPMA at the ~100 µg g‐1 level. Even for mounts not polished with alumina photoelectron spectroscopy shows high levels of Al surface contamination. In order to minimise electron beam current density, a rastered 50 × 100 µm electron beam was adequate and minimised sensitivity to small Al‐rich contaminants. Reproducible analyses of eleven SIMS cleaned spots on San Carlos olivine agreed at 69.3 ± 1.0 µg g‐1. The known Al mass fraction was used to calibrate an Al implant into San Carlos. Accurate measurements of Al were made for olivines in the pallasites: Imilac, Eagle Station and Springwater. Our focus was on Al in olivine; but our technique could be refined to give accurate electron probe measurements for other contamination‐sensitive trace elements. For solar wind it is projected that the Al/Mg abundance ratio can be determined to 6%, a factor of 2 more precise than the solar spectroscopic ratio.
Simplified expressions for calculating nucléon momentum distributions are derived in the context of the harmonic oscillator shell model and in its modification in which fractional occupation probabilities of the surface orbits are used. The method is applied to study the proton momentum distribution of the spherical nucleus 40Ca. The values of the partial occupation probabilities used had been previously determined by fitting to the experimental elastic form factor data.
Ionic liquids provide a unique opportunity to study the surface structure of liquids using a variety of surface analysis techniques. This chapter reviews the results of high‐resolution Rutherford backscattering spectroscopy (HR‐RBS) studies on the surface structures of typical ionic liquids, i.e. imidazolium‐based ionic liquids, and their binary mixtures. The results obtained by other techniques are briefly compared with the HR‐RBS results. The agreement with the HR‐RBS profiles is improved dramatically, demonstrating that the molecular dynamics simulation is a reliable method to study the surface structures of ionic liquids. The HR‐RBS measurements show moderate surface enrichment of larger ionic liquids for the mixtures studied. There are apparent discrepancies in the observed surface enrichment between HR‐RBS and some other surface analysis techniques, namely time‐of‐flight secondary ion mass spectrometry, low‐energy ion scattering, and X‐ray photoelectron spectroscopy.
We review, summarize and augment our recent studies on the problem of using Secondary Neutral Mass Spectrometry method for analyzing PbTe, SnTe and GeTe binary tellurides specimens. The experimental results are discussed with reference to the chemical diversity of the studied compounds, preferential sputtering of their constituents manifesting itself differently in the different tellurium compounds; the large differences in atomic masses of the telluride components; and the morphology of the sputtered surfaces, which has been characterized by means of scanning electron microscopy.
A thesis submitted by Munthala Dhanunjaya in the partial fulfilment of the requirement for the award of the degree of Doctor of Philosophy in Physics Under the supervision of Prof. S. V. S Nageswara Rao and Prof. A. P Pathak
The method of Rutherford backscattering (RBS) of ⁴He ions is used to detect impurities in the surface region of natural diamond crystals. In order to decrease the influence of luminescence from the surface of diamond, the recording of scattered ions is performed by an annular detector, which decreases the statistical error and improves the measurement accuracy. The limit of impurity detection is 10¹⁴ at/cm² for light impurities and 10¹² at/cm² for heavy impurities.
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