To be Updated with new approved abstracts

Background. The relevance of x-ray production cross sections (XRPCS) and the related ionization cross sections (ISC) in many research as has been described at length and analyzed in detail [Miranda and Lapicki 2014]. X-ray emission cross sections by ion impact are a relevant input in many areas such as e.g., as for studies of track structure in DNA [Lekadir et al. 2009] or in water [Backstrom et al. 2013]. Particle Induced X-ray Emission (PIXE) strongly requires trustworthy databases for XRPCS and/or reliable predictions of inner-shell ionization theories as periodically evaluated in Monte Carlo Geant4 simulations [Pia et al. 2010 Incerti et al. 2015].
Purpose. To present 1) a review of the PIXE technique and its applications, and 2) universal experimental and theoretical [ECUSAR theory of Lapicki 2001] fits to existing databases for K- and L-shell XRPCS.
Goals. To check if the theory is accurate across the periodic table of elements and a large range of projectile energies, equally comprehensive databases are essential and a universal fit for them is desired. Those fits should be in terms of a variable by which XRPCS are scaled with a minimum of adjustable parameters.
Conclusions. The versatility of the PIXE technique and its application will be demonstrated. It will be shown how universal experimental and theoretical fits to XRPCS serve to set reliable predictions across projectile energies and a wide range of target elements for accurate analysis of elements in materials.

Assessing ferroelectricity in thin films or single crystals is of crucial importance whenever these materials are to be integrated in electronic devices for applications to e.g. memories, low consumption transistors or sensors. For all these applications, it has become mandatory to measure ferroelectricity at the nanoscale. One of the most popular tools to do so is Piezoresponse Force Microscopy (PFM) which is derived from Atomic force Microscopy (AFM), and allows to map ferroelectric domains, to obtain hysteresis loops at the nanoscale as well as to write domains by the application of voltages between the tip and the sample. We describe in this communication the capabilities of such a technique. But since several years, PFM has lead to severe misinterpretations because some non-ferroelectric layers have lead to perfect PFM images and loops. We will explain the origins of these misinterpretatations and propose an alternative method based on current measurements (nano-PUND), which seems to be more powerful and less sensitive to artefacts than PFM when ferroelectricity has to be assessed.

Chalcogenide semiconductors, in particular CdTe and Cu(In,Ga)Se2 (CIGS), have achieved great progress in performance of photovoltaic materials recently. However, they present a challenge to understand, as they perform better as polycrystalline materials than as single crystals. Therefore, it is necessary to understand how the films grow and in particular how grain boundaries affect the devices. This talk presents an overview of two scanning probe methods, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) applied to this question. In particular, two modifications to AFM are applied, conductive AFM and scanning microwave impedance microscopy (SMIM) to understand local variations in carrier density and conduction. The results show how band edge fluctuations at the atomic scale can prevent atomic resolution imaging and how grain boundary properties differ from the bulk behaviors. CIGS shows large variations in both band edges on the atomic scale. Thus, choosing one tip bias results in large changes in current driven by the fluctuations and hence to changes in tip height not resulting from atomic features but rather from electronic behaviors. AgInSe2 shows smaller variations in the valence band edge and produces excellent atomic-resolution images when tunneling out of the surface but not when tunneling into the conduction band. It is shown that CdTe grain boundaries exhibit depleted majority hole concentrations relative to the grain bulk. This will induce collection of electrons to the boundaries. The resulting separation of the electrons from the holes reduces recombination. Conductive AFM shows that the boundaries are pathways for collection of current by the device. Remarkably, current injected directly into the boundary travels in the boundary rather than crossing into the grains while current injected in the grains stays in the grains. By contrast CIGS does not show this behavior and grain boundaries are very similar in overall behavior to grains. Implications of these results for the devices are described.

Grain boundaries (GBs) are important elements of photovoltaic devices. Usually, they act as effective recombination sinks and limit the conversion efficiency of low cost silicon solar cells, but in devices employing compound semiconductors the role of GBs is not that obvious as their presence is also considered to be beneficial. Since, in either case, the knowledge of electronic properties of GBs is crucial for further improvements, we first discuss experimental techniques allowing for characterization of the electronic activity of GBs as well as analytical approaches relating the properties of GBs to the carrier transport mechanisms. However, due to the complexity of the system, the application of such simple models for the interpretation of real data is very often not straightforward. Therefore, we further focus on more advanced topics, such as metastable defects, taking as an example Cu(In,Ga)Se2- based solar cells.

Cu(In,Ga)Se2 thin film solar cell technology has recently achieved the outstanding power conversion efficiency of 22.6 %. Such level of performance is surprising because these devices are based on polycrystalline layers and hetero-junctions; hence implying numerous homo- and hetero-interfaces.
Nevertheless, the recent efficiency breakthrough was made possible thanks to specific post- deposition treatments of the Cu(In,Ga)Se2 absorber, which imply both surface and grain boundary modifications. So far, the best solar cells were prepared from absorbers which were treated by heavy alkali fluoride, namely KF or RbF.
The present contribution aims at presenting and discussing the various models proposed up to date to explain grains and grain boundary modifications and their influence on the related solar cell performance.

Crystalline films of small conjugated molecules offer attractive potential for fabricating organic solar cells, organic light emitting diodes (LED), and organic field effect transistors (OFETs) on flexible substrates. Here, the novel two-dimensional (2D) van der Waals materials like conducting graphene (Gr) or insulating ultrathin hexagonal boron nitride (hBN) come into play. Gr, for instance, offers potential application as a transparent conductive electrode in organic solar cells and LEDs replacing indium tin oxide, whereas hBN can be used as a ultrathin flexible dielectric in OFETs.
We report on the self-assembly of crystalline needles composed of rod-like molecules on exfoliated, wrinkle-free Gr and hBN, both transferred onto SiO2. The needles are several 10 nm wide and a few nm high, they can extend to several 10 µm in length. The discrete needle directions with respect to armchair and zigzag directions of the substrates were determined by atomic-force microscopy (AFM).
Through in-situ measurements during molecule deposition on Gr in field-effect transistor device geometries, the charge transfer at the interface was directly probed. The amount of charge transferred per adsorbed molecule is only about one thousandth of an electron transferred per molecule. Further, electrostatic force microscopy (EFM) based charging and charge spreading experiments demonstrate the optoelectronic properties of the organic nanoneedles.

WO3, MoO3, and V2O5 are famous “hydrogenphilics” capable of accommodating of great quantities of hydrogen atoms, which yields dramatic changing of the optical parameters. Photoinjection of atomic hydrogen was carried out into the oxide films; hydrogen being split off from adsorbed hydrogen-containing molecules (hydrogen donors) previously adsorbed on the oxide surface via a photochemical reaction. Being an excellent reducing agent, often a latent agent, and playing the role of a dopant or a catalyst, sometimes, combining both functions, atomic hydrogen triggers various processes on the solid surface. The adsorption mechanism for specially selected organic molecules (hydrogen donors) has been described. The great catalytic effect for the photochemical reaction of abstraction of hydrogen atoms from the adsorbed organic molecules has been achieved due to formation of donor-acceptor and hydrogen bonds, which perturbs both electronic and ionic systems of the molecules. The experiments, carried out in the wide temperature range, made it possible to consider the reaction mechanism as the proton-coupled electron transfer (PCET) between the adsorbed molecule and the oxide surface. A non-zero low temperature reaction rate limit was discovered, which is a reliable evidence for a tunneling mechanism reaction. The changes in the oxide optical properties in the wide spectral range upon insertion of hydrogen atoms have been considered. Special attention has been paid to formation of different color centers: bulk and surface (paramagnetic and diamagnetic). The nature of the giant shift of the fundamental absorption edge in the V2O5 nanocrystalline has been discussed. The function of the photochemical hydrogen as a catalyst for surface chemical reaction, yielding formation of other nanostructures, has been investigated. Several examples of hydrogen photosensitization carried out simultaneous to illumination in silver and cuprous halides are presented. The performances of the nano-heterostructures employing hydrogen photo-initiated spillover are discussed. The function of the photochemical hydrogen as a catalyst for secondary surface photochemical reactions has been shown. Several examples of hydrogen photosensitization carried out simultaneous to illumination in silver and cuprous halides have been observed in the double-layer structures: AgCl-WO3, AgI-WO3, RbAg4I5-WO3, and CuCl-WO3. First, the direct PIH into the WO3 films has been carried out, and then the detached hydrogen atoms migrating into the halide layer provided formation of sensitization centers, which enhanced the photolysis of the halides. The currently proceeding investigations have been showed the perceptiveness of the multifunctional materials on the base of the transition metal oxides either for fundamental or applied research.

Friction is known to be a multi-scale phenomenon which starts at the atomic or molecular scale, and emerges at the macro-scale by means of the so-called real contact area. This multi-scale process generally involves some self-organization processes within this real contact area, which generally occurs with the reduction of the number of degrees of freedom. Hence, macro-scale properties of physical systems – such as the coefficient of friction, the Young modulus, the yield strength, or the fracture toughness – cannot be deduced directly from the molecular scale properties because these properties are defined by meso-scale objects such as defects, grains, and asperities – especially, roughness for tribological purpose. Thus, (i) tribological properties – including friction and wear processes – need to be studied by considering a multi-scale approach, in order to understand how these phenomena emerge from atomic to macroscopic scale; (ii) specific emerging tribological behaviors can be tailored or adjusted by means of self-assembled monolayers or hierarchical surfaces or materials.
In this paper, this approach will be illustrated by considering various tribological studies, which have been investigated at various scales in our respective teams.

To ensure the general breakthrough of electrical vehicles in our modern society it is highly desirable to improve performance, safety and lifetime of current batteries, fuel cells and hydrogen storage systems. It is commonly thought that such improvements are found within the so-called all-solid-state energy devices. To accomplish a paradigm shift within this field a new generation of energy materials needs to be developed. Further, a better understanding of how surface and interface effects are potentially affecting intrinsic material properties is clearly needed. Muon spin rotation and relaxation (mu+SR) is a hidden gem among the available experimental techniques. Its extreme sensitivity to static and dynamic electronic as well as nuclear fields makes it ideal to study especially ion dynamics in solid energy materials. It is also one of the very few techniques that is able to acquire non-destructive depth profiling of ion diffusion across an interface. In this presentation I will briefly outline the working principle of this unique method and show its capabilities through our recent results from studies of batteries as well as hydrogen storage materials.

Intermetallic compounds are known as highly selective, effective and long-lasting new generation catalysts in processes of green hydrogen production via methanol steam reforming and carbon dioxide reduction to methanol and production of plastics on the way of semi-hydrogenation of acetylene. Adsorption properties of surfaces play a key role and are determined predominantly by electronic effects, while geometrical and vibrational properties of the adsorbate-substrate complex provide 'fine-tuning' of the adsorption behavior. Numerous studies investigating the hydrogenation of acetylene and ethylene have lead to the development of the active site isolation concept. For this weakly adsorbed acetylene where the Ï€-bonds are interacting with the surface (Ï€-adsorbed acetylene) will be transformed to ethylene (the desired chemical reaction), while stronger di-σ adsorbed acetylene will undergo undesired full hydrogenation or form carbonaceous deposits that will deactivate the catalyst. Basic idea of the active-site-isolation concept is to surround the catalytically active atoms by atoms of another inactive chemical element, so that the active atoms are isolated by spatial separation. The isolated active sites show preference for the Ï€-adsorbed acetylene, resulting in high selectivity for the semiehydrogenation of acetylene to ethylene, while in the absence of spatial separation (i.e., when many active atoms are close neighbors) the catalyst material is less selective. Intermetallic compounds GaPd, GaPd₂ and Ga₇Pd₃ were demonstrated to show superior catalytic selectivity and stability over the commercial Pd-based catalysts in the semi-hydrogenation of acetylene in a large excess of ethylene, which is an important step in the purification of the ethylene feed for the production of polyethylene. The selectivity of these compounds to ethylene was reported to be between 65 and 75%, which is much higher than that of a commercial Pd/Al₂O₃ supported catalyst, where a selectivity of 15-20% was reported for the 5% Pd/Al₂O₃. High selectivity is considered to result from specific crystalline structures of these compounds, while good stability under the reaction conditions originates from strong covalent chemical bonding in the structure. The metallic character of the Ga-Pd compounds also allows for a substantial electronic density of states (DOS) near the Fermi level, which is a prerequisite for facile activation of di-hydrogen H2 as a reactant. The difference in selectivity between these compounds was found small, with the GaPd₂ selectivity being the highest and that of Ga₇Pd₃ the lowest. I shall present electronic, thermal and magnetic properties of the Ga-Pd phases along orthogonal directions of the structures. By using ⁶⁹Ga and ⁷¹Ga NMR spectroscopy, the electric-fieldgradient (EFG) tensor at the Ga site in the unit cell and the Knight shift, which yields the electronic DOS at the Fermi energy ε_F were determined. Since the catalyst material in a chemical reaction should exhibit as large surface as possible, the nanoparticle morphology of the material is preferred under realistic conditions, but the physical properties of the nanoparticles may differ substantially from those of the bulk. To see the change of electronic properties of the GaPd₂ phase on going from the bulk material to the nanoparticles morphology, the GaPd₂/SiO₂ supported nanoparticles were synthesized and determined their electronic DOS at ε_F from the ⁷¹Ga NMR spin-lattice relaxation rate, which was then compared to the DOS of the bulk. This work complements recent studies of physical properties of the GaPd and InPd intermetallic catalysts.

There is the widespread opinion within the research community of hydrogen storage materials, that their nanocrystalline structure is a precondition for enhancement of the kinetics of hydrogen absorbtion/desorption, by means of enhanced diffusion of H2 along the grain boundaries. Examples for this behavior are presented, including ball milled, filed and/or SPD processed Mg, Mg- and Fe-alloys. SPD (Severe Plastic Deformation) represents a new method processing method to achieve bulk nanocrystalline materials. Considering more than one storage cycles in pure Mg, the kinetics and even the storage capacity is drastically decreased. One may find the reason in the strongly increased grain size because of the comparably high absorption/desorption temperature of 350°C. However, in the SPD processed Mg-alloys like ZK60, the kinetics and the storage capacity do not decrease with repeated absorption/desorption cycles, although the average grain size significantly increases. Thus it is concluded that the grain size effect beneficial to storage kinetics during the first cycles must have a reason other than hydrogen grain boundary diffusion. Recent DFT calculations within a research project of the authors suggest that the dissocation of H2 to H - which is a precondition of successful absorption of hydrogen by the host material - occurs more easily at the surface and especially in the wake of crystal defects being present at the surface. Experiments by the authors done in Mg-alloys and Fe-Ti having various initial ball milling particle sizes and/or grain sizes confirm this conclusion. Furthermore, recent experiments both from literature and from the authors showed that application of SPD can save the pulverization and/or filing of the H2 storage materials, by providing not only high densities of grain boundaries but also those of microcracks at the surface.

This paper presents the results of the investigation of stresses relaxation by strain, by means of EPR spectra, SEM, and samples deflection. It has been shown that stresses relaxation mechanism depends on the oxidation condition: temperature, cooling rate, oxide thickness. In the Si-SiO2-Si3N4 system, the stresses relaxation occurs due to the opposite sign of the thermal expansion coefficient of SiO2 and Si3N4 on Si. With an appropriate oxidation condition choice, compressive stresses in SiO2 and tensile stresses in Si are nearly equal and disappear on the interface.

Nanostructure materials have been the subject of widespread research over the past couple of decades. Recent experiments on nanostructure materials have revealed a host of novel physical and chemical properties, which are significantly different from that of the conventional materials. Many workers are devoted to developing new synthesis methods to fabricate materials with novel nanostructures. ZnS, as a vital wide-gap semiconductor, has been extensively investigated due to its outstanding photoelectric effect, high catalytic activity and wide applications. Recently, ZnS nanomaterials with various geometrical shapes such as 1D wire, rod, or 2D sheet, belt and so on, have been prepared using variety of physical or chemical methods [1-2]. Dandelion-like ZnS materials assembled by 2D nanosheets or 1D nanowires are of great interest as they provide extremely large specific surface areas and unique porous microstructure [3]. However, research into the 3D nanostructure ZnS assembled by 1D ZnS nanowires is still less dealt with. What¡¯s more, majority researchers were devoted to photoluminescence and photocatalytic, few of them pay enough attention to the antibacterial activity of ZnS.
Microbial contamination has become increasing difficult to control owing to the resistance offered by microbes against conventional antimicrobial agents. It is well-know that inorganic nanomaterials, such as TiO2, AgPO3, ZnO, reveal high antibacterial activities [4-5]. To date, only scant information about antibacterial ability of the ZnS has been recorded. In this work, dandelion-like ZnS has been prepared via the method of facile one-pot hydrothermal synthesis. The dandelion-like ZnS was characterized by transmission electron microscope, scanning electron microscope, energy dispersive spectrometer and X-ray diffraction. The results reveal that the surface topographies of the 3D dandelion-like ZnS particles are actually assembled by plenty of interlaced 1D ZnS nanowires. The influence of reaction time, reaction temperature, Zn/S mole ratio and different zinc and sulfur sources to the dandelion-like structure were investigated. The dandelion-like ZnS exhibits superior ability in inhibiting the growth of Escherichia coli, which makes it promising candidate for biological materials. The large specific surface area, porous surface morphology and the releasing of the Zn2+ ions are considered probable causes for the high antibiotic activity of the dandelion-like ZnS.

Permanent magnets based on Nd-Fe-B are the highest energy magnets for more than 30 years and are vital components in the rapidly-developing renewable energy sector, where the motors for electric vehicles and the generators in wind turbines require strong magnets with the ability to operate at temperatures well over 100�C. In 2014 EU published a new list of critical raw materials (CRM). Regarding supply risk, the rare earth was considered to be by far the most problematic and especially the heavy rare earth (HRE) are far above all light rare earth. Since HRE such as dysprosium or terbium is required to assure the high-temperature performance of the magnets, our research has focused on drastic decrease the amount of this elements and to achieve the same quality in sintered magnets as well as in the basic powers used for bonded magnets.
Our research was focused on HRE free Nd-Fe-B melt spun ribbons doped with small amounts of DyF3 to improve the coercivity and to minimize the need for HRE. We will report on the correlation between magnetic properties, the amount of the additive, and the processing parameters. The explanation of the HRE influence on the improved properties will be based on microstructural analysis using high-resolution electron microscopy and chemical analyses. We will show that the addition of DyF3 up to 2.2 wt.% to the melt-spun powder showed a positive effect on the Hci of the heat-treated samples. The maximum coercivity (Hci) achieved represents a 25 % increase over the untreated samples.
The interphase between the grains was thoroughly studied. The EEL results, which confirmed EDX investigations showed in the case of annealed sample the (Dy, Nd)-Fe-B phase formation at the shell around the pure Nd-Fe-B core grains. The high increase in Hci is strongly linked with the heat-treatment process where Dy diffused along grain boundaries into the outer parts of Nd-Fe-B grains and partial substitute Nd by Dy forming core-shell-like grains. We will document that fluorine does not penetrate into the grains but it accumulates in the grain boundary regions. Furthermore, the thermal gravimetric reaction coupled with mass spectroscopy revealed that none of the toxic fluorine-based compounds evaporate or form during heat-treatment to 1200 �C. Therefore, we can conclude that our technique for boosting the Nd-Fe-B magnets with small amount of DyF3 is one of the most efficient and environment safe processes.

A solar cell is a device that converts a solar energy into an electric current. Studying the properties of the absorber layer is a key point to optimize its conversion efficiency. In this study, we focus on polycrystalline CuIn1-xGaxSe2 (CIGSe), which is one of the most promising absorber layers for solarcells. So far, best labscale energy conversion efficiencies are achieved for x = [Ga]/([Ga]+[In]) ¡O0.3, while the theoretical x-dependent cell efficiency curve predicts better performances for x ¡O0.75. One possible explanation is that Grain Boundaries (GBs) play a specific role as a function of x. We suggest 2 possible phenomena that can occur at the CIGSe GBs: first, The interface and the grain interior compositions differ, and the nature of the predominant species at the interface varies with x. This is consistent with i) recent results obtained by APT (Atom Probe Tomography), and ii) our simple theoretical-based model of segregation driving forces that combine ab initio and statistical thermodynamics. Secondly, a detrimental solid solution can accumulate within the GBs. Our XRD, RAMAN and EDS analyses demonstrate a different behavior of a Cu-rich compound at low and high Ga-ratio. The nature of the accumulated species or compound at the interface can be detrimental or beneficial for the solar cell efficiency. Hence, in this contribution we discuss both experimentally and theoretically these two scenarios.