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In order to effectively utilize the photovoltaic properties of gallium arsenide, its surface/interface needs to be properly prepared. In the experiments described here we examined eight different paths of GaAs surface treatment (cleaning, etching, passivation) which resulted in different external quantum efficiency (EQE) values of the tested photovoltaic (PV) cells. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examinations were conducted to obtain structural details of the devices. X-ray photoelectron spectroscopy (XPS) with depth profiling was used to examine interface structure and changes in the elemental content and chemical bonds. The photoluminescence (PL) properties and bandgap measurements of the deposited layers were also reported. The highest EQE value was obtained for the samples initially etched with a citric acid-based etchant and, in the last preparation step, either passivated with ammonium sulfide aqueous solution or treated with ammonium hydroxide solution with no final passivation. Subsequent I–V measurements, however, confirmed that from these samples, only the sulfur-passivated ones provided the highest current density. The tested devices were fabricated by using the ALD method.

Aleksandra Seweryn,1 Ariadna Pielok,2 Krystyna Lawniczak-Jablonska,1 Rafal Pietruszka,1 Klaudia Marcinkowska,2 Mateusz Sikora,2 Bartlomiej S Witkowski,1 Marek Godlewski,1 Krzysztof Marycz,2,3 Agnieszka Smieszek2 1Institute of Physics, Polish Academy of Sciences, Warsaw PL-02668, Poland; 2Wroclaw University of Environmental and Life Sciences, Department of Experimental Biology, Wroclaw PL-50375, Poland; 3Cardinal Stefan Wyszynski University, Collegium Medicum, Warsaw PL-01938, PolandCorrespondence: Aleksandra SewerynPolish Academy of Sciences, Aleja Lotnikow 32/46, Warsaw PL-02668, PolandTel +48 22 116 33 99Fax +48 22 843 09 26Email aseweryn@ifpan.edu.plAgnieszka SmieszekWroclaw University of Environmental and Life Sciences, Norwida St. 27 B, Wroclaw PL-50-375, PolandTel +48 71 320 5229Fax +48 22 843 09 26Email agnieszka.smieszek@upwr.edu.plIntroduction: The development of the field of biomaterials engineering is rapid. Various bioactive coatings are created to improve the biocompatibility of substrates used for bone regeneration, which includes formulation of thin zirconia coatings with pro-osteogenic properties. The aim of this study was to assess the biological properties of ZrO2 thin films grown by Atomic Layer Deposition (ALD) technology (ZrO2ALD).Methodology: The cytocompatibility of the obtained layers was analysed using the mice pre-osteoblastic cell line (MC3T3) characterized by decreased expression of microRNA 21-5p (miR-21-5p) in order to evaluate the potential pro-osteogenic properties of the coatings. The in vitro experiments were designed to determine the effect of ZrO2ALD coatings on cell morphology (confocal microscope), proliferative activity (cell cycle analysis) and metabolism, reflected by mitochondrial membrane potential (cytometric-based measurement). Additionally, the influence of layers on the expression of genes associated with cell survival and osteogenesis was studied using RT-qPCR. The following genes were investigated: B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), p53 and p21, as well as osteogenic markers, i.e. collagen type 1 (Coll-1), osteopontin (Opn), osteocalcin (Ocl) and runt-related transcription factor 2 (Runx-2). The levels of microRNA (miRNA/miR) involved in the regulation of osteogenic genes were determined, including miR-7, miR-21, miR-124 and miR-223.Results: The analysis revealed that the obtained coatings are cytocompatible and may increase the metabolism of pre-osteoblast, which was correlated with increased mitochondrial membrane potential and extensive development of the mitochondrial network. The obtained coatings affected the viability and proliferative status of cells, reducing the population of actively dividing cells. However, in cultures propagated on ZrO2ALD coatings, the up-regulation of genes essential for bone metabolism was noted.Discussion: The data obtained indicate that ZrO2 coatings created using the ALD method may have pro-osteogenic properties and may improve the metabolism of bone precursor cells. Given the above, further development of ZrO2ALD layers is essential in terms of their potential clinical application in bone regenerative medicine.Keywords: ALD, zirconia-based coatings, pro-osteogenic properties, cytocompatibility, osteoblasts precursors

Numerous efforts have already been made to optimize nitridation of crystalline sapphire (c-Al2O3) substrates whereas very little attention has been paid to nitridation of amorphous aluminum oxide layers (a-AlOx). An extensive analysis of the reaction of amorphous aluminum oxide films with nitrogen species is thus needed to clarify the mechanisms of nitrogen incorporation into such layers and to control their properties. In this work X-ray photoelectron spectroscopy was used to determine the chemical state of nitrogen formed by nitrogen plasma treatment of c-Al2O3 and 15 nm thick a-AlOx layers grown by atomic layer deposition on Si and sapphire substrates. The results show that the nitridation proceeds significantly different for c-Al2O3 and a-AlOx samples, which we correlate with the initial stoichiometry of both materials. At the surface of sapphire O vacancies were found, which are necessary for the formation of AlN-type bonding via diffusion limited replacement of oxygen by nitrogen. This process was slow and involved formation of oxinitride AlN–O. After 80 min of nitridation only ∼3.4 at% of N was incorporated. In contrast, in a-AlOx layers Al vacancies were present before nitridation. This opened a new, more effective path for nitrogen incorporation via accumulation of N in the cation-deficient lattice and creation of the Al(NOy)x phase, followed by AlN and AlN–O formation. This scenario predicts more effective nitrogen incorporation into a-AlOx than c-Al2O3, as indeed observed. It also explains our finding that more N was incorporated into a-AlOx on Si than on sapphire due to supply of oxygen from the sapphire substrate.

The continuous development of ALD thin films demands ongoing improvements and changes toward fabricating materials with tailored properties that are suitable for different practical applications. Ozone has been recently established as a precursor, with distinct advantages over the alternative oxidizing precursors in the ALDs of advanced dielectric films. This study reports alumina (Al2O3) and hafnia (HfO2) formation using an O3 source and compares the obtained structural and electrical properties. The performed structural examinations of ozone-based materials proved homogenous high-k films with less vacancy levels compared to water-based films. The enhanced structural properties also result in the problematic incorporation of different dopants through the bulk layer. Furthermore, analysis of electrical characteristics of the MIS structures with ALD gate dielectrics demonstrated the improved quality and good insulating properties of ozone-based films. However, further optimization of the ALD technique with ozone is needed as a relatively low relative permittivity characterizes the ultra-thin films.

The experimental and theoretical studies of the local atomic order and chemical binding in tantalum oxide amorphous films are presented. The experimental studies were performed on thin films deposited at the temperature of 100 °C by atomic layer deposition on silicon (100) and glass substrates. Thin films of amorphous tantalum oxide are known to exhibit an extremely large extent of oxygen nonstoichiometry. Performed X-ray absorption and photoelectron studies indicated the oxygen over-stoichiometric composition in the considered films. Surplus oxygen atoms have 1s electron level with binding energy about 1 eV higher than these in reference Ta2O5 oxide. The density functional theory was applied to find the possible location of additional oxygen atoms. Performed calculation indicated that additional atoms may form the dumbbell defects, which accumulate the dangling oxygen bonds in orthorhombic structure and lead to increase of oxygen 1s level binding energy. The presence of this kind of oxygen–oxygen bonding may be responsible for increase of amorphous film chemical resistivity which is very important in many applications.

In order to effectively utilize the photovoltaic properties of gallium arsenide, its surface/interface needs to be properly prepared. In the experiments described here we examined eight different paths of GaAs surface treatment (cleaning, etching, passivation) which resulted in different external quantum efficiency (EQE) values of the tested photovoltaic (PV) cells. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) examinations were conducted to obtain structural details of the devices. X-ray photoelectron spectroscopy (XPS) with depth profiling was used to examine interface structure and changes in the elemental content and chemical bonds. The photoluminescence (PL) properties and bandgap measurements of the deposited layers were also reported. The highest EQE value was obtained for the samples initially etched with a citric acid-based etchant and, in the last preparation step, either passivated with ammonium sulfide aqueous solution or treated with ammonium hydroxide solution with no final passivation. Subsequent I–V measurements, however, confirmed that from these samples, only the sulfur-passivated ones provided the highest current density. The tested devices were fabricated by using the ALD method.

Atomic layer deposition (ALD) technology has started to attract attention as an efficient method for obtaining bioactive, ultrathin oxide coatings. In this study, using ALD, we have created titanium dioxide (TiO2) layers. The coatings were characterised in terms of physicochemical and biological properties. The chemical composition of coatings, as well as thickness, roughness, wettability, was determined using XPS, XRD, XRR. Cytocompatibillity of ALD TiO2 coatings was accessed applying model of mouse pre-osteoblast cell line MC3T3-E1. The accumulation of transcripts essential for bone metabolism (both mRNA and miRNA) was determined using RT-qPCR. Obtained ALD TiO2 coatings were characterised as amorphous and homogeneous. Cytocompatibility of the layers was expressed by proper morphology and growth pattern of the osteoblasts, as well as their increased viability, proliferative and metabolic activity. Simultaneously, we observed decreased activity of osteoclasts. Obtained coatings promoted expression of Opn, Coll-1, miR-17 and miR-21 in MC3T3-E1 cells. The results are promising in terms of the potential application of TiO2 coatings obtained by ALD in the field of orthopaedics, especially in terms of metabolic- and age-related bone diseases, including osteoporosis.

Background Due to increasing aging of population prevalence of age-related disorders including osteoporosis is rapidly growing. Due to health and economic impact of the disease, there is an urgent need to develop techniques supporting bone metabolism and bone regeneration after fracture. Due to imbalance between bone forming and bone resorbing cells, the healing process of osteoporotic bone is problematic and prolonged. Thus searching for agents able to restore the homeostasis between these cells is strongly desirable. Results In the present study, using ALD technology, we obtained homogeneous, amorphous layer of hafnium (IV) oxide (HfO2). Considering the specific growth rate (1.9Å/cycle) for the selected process at the temperature of 90 °C, we performed the 100 nm deposition process, which was confirmed by measuring film thickness using reflectometry. Then biological properties of the layer were investigated with pre-osteoblast (MC3T3), pre-osteoclasts (4B12) and macrophages (RAW 264.7) using immunofluorescence and RT-qPCR. We have shown, that HfO2 (i) enhance osteogenesis, (ii) reduce osteoclastogenesis (iii) do not elicit immune response and (iv) exert anti-inflammatory effects. Conclusion HfO2 layer can be applied to cover the surface of metallic biomaterials in order to enhance the healing process of osteoporotic bone fracture.

SnS and SnS

Two new Ba(II) and Pb(II) citrate coordinate polymers have been synthesized and structurally characterized. The crystalline complexes have been obtained using the gel method. The high purity of synthesized compounds has been confirmed by the X-ray photoelectron study. The deprotonation of citric acid and metal-carboxylate ligand binding has been observed in the XPS as well as IR spectra. The crystal structure of both complexes has been determined by X-ray crystallography, thus being the first crystal structure of Ba(II) citrate and only the second one of Pb(II) citrate reported in literature. Both hydrated complexes: {[5Ba(C6H5O7)2(C6H6O7)2·6H2O]·2H2O}n and {[5.5Pb(C6H5O7)3(C6H6O7)·5H2O]·4.5H2O}n are three-dimensional polymers with four crystallographically distinct citrate groups, which differ in charges and chelating modes. The O-atoms from organic and aqua ligands are nearly symmetrically distributed around the Ba(II) anions, whereas the Pb(II) cations display hemidirected coordination geometries. These metal-citrate moieties as well as the very complex hydrogen-bonding scheme, which arises from the superabundance of donors and acceptors, lead to the stable structures of both complexes. Additional insight into the electronic structure of the studied compounds, and in particular the properties of stereochemically active lone electron pair on Pb(II) ion, has been gained from the periodic density functional theory calculations.

Novel optical sensors the most often require thin films or surface structures with strictly controlled properties, playing a critical role in them by initiating or modifying their sensorial responses. Selected results of research on atomic layer deposited (ALD) metallic oxides will be shown, regarding their applicability for thin functional coatings in lossy mode resonance (LMR) and long period grating (LPG) optical fiber sensors. Basically amorphous films of tantalum oxide (TaxOy), zirconium oxide (ZrxOy) and hafnium oxide (HfxOy) below 200 nm were deposited at relatively low temperature (LT) of 100°C. The optical, structural, topographical, tribological, hydrophilic and chemical stability properties of the films and their technological controllability were analysed. The TaxOy was selected and successfully applied as an oxide coating in LPG sensor. As chemically robust in alkali environment (pH over 9) it allowed to gain a potential for fabrication of regenerable/reusable biosensor. Additionally, ALD technique was tested as a tool for tailoring sensorial properties of LMR sensors. The double-layer coatings composed of two different materials were experimentally tested for the first time; the coatings were composed of plasma-enhanced chemical vapour deposited (PECVD) silicon nitride (SixNy) followed by much thinner ALD TaxOy. That approach yielded operating devices, ensuring fast overlay fabrication and easy tuning of the resonant wavelength at the same time. The LT ALD TaxOy films turned out to be slightly overstoichiometric (y/x approx. 2.75). Therefore, the issue of TaxOy chemical composition was studied by secondary ion mass spectroscopy, Rutherford backscattering spectrometry and x-ray photoelectron spectrometry.

Recently, extreme ultraviolet (EUV) radiation has been increasingly used to modify polymers. Properties such as the extremely short absorption lengths in polymers and the very strong interaction of EUV photons with materials may play a key role in achieving new biomaterials. The purpose of the study was to examine the impact of EUV radiation on cell adhesion to the surface of modified polymers that are widely used in medicine: poly(tetrafluoroethylene) (PTFE), poly (vinylidene fluoride) (PVDF), and poly-L-(lactic acid) (PLLA). After EUV surface modification, which has been performed using a home-made laboratory system, changes in surface wettability, morphology, chemical composition and cell adhesion polymers were analyzed. For each of the three polymers, the EUV radiation differently effects the process of endothelial cell adhesion, dependent of the parameters applied in the modification process. In the case of PVDF and PTFE, higher cell number and cellular coverage were obtained after EUV radiation with oxygen. In the case of PLLA, better results were obtained for EUV modification with nitrogen. For all three polymers tested, significant improvements in endothelial cell adhesion after EUV modification have been demonstrated.

SnS and SnS2 powders were synthesized with the use of ultrasound. The indirect sonication was applied with ultrasound frequency 40 kHz and acoustic power 38 W/L. Products of syntheses were examined with PXRD, TEM, EDX, XPS, and UV–Vis (the Tauc method) investigations. The resulting microparticles were used for tip coating of copper cathodes. These electrodes were used in the degradation of model azo-dye Metanil Yellow by the electro-Fenton process. The efficiencies of degradation using copper, SnS-coated copper, and SnS2-coated copper cathodes are compared. Kinetics of degradation of Metanil Yellow in the electro-Fenton process with the application of three different cathodes is also investigated. It was found that the degradation follows pseudo-first-order and that SnS-coated copper cathode improves the efficiency of degradation, while SnS2-coated copper cathode decreases the efficiency of degradation.

Relationship between variation of Bi and O valence states in perovskite bismuthates Ba1-xKxBiO3 (BKBO), grown in modified synthesis conditions, and their superconducting state properties is presented. Chemical composition, crystal structure and phase purity of BKBO was determined via micro X-ray fluorescence ( μ XRF), energy-dispersive X-ray spectroscopy (EDS) and X-ray powder diffraction technique (XRD). X-ray photoemission spectroscopy (XPS) and SQUID magnetometry showed variations of electronic structure and superconducting state properties, i.e., lower and upper critical fields, and transition temperature for the samples synthesized at various conditions. We report that, multiple valencies of bismuth, observed already in BKBO systems and assigned to disproportionation of bismuth valence states, lead in fact to deterioration of superconducting state properties.

Double metal cyanide (DMC) catalysts are commonly applied at industrial ring-opening polymerization of the epoxides, being the initial stage of the polyurethanes manufacturing route. This group of catalysts is frequently used in industry, but the knowledge on the molecular nature of their high activity and selectivity is limited to some phenomenological hypotheses based on overall chemical premises. To shine some light on the relation between structural and chemical properties of DMC catalysts and their activity, the complementary X-ray powder diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and X-ray absorption spectroscopy studies were performed. The comprehensive characterization of DMC catalyst synthesized from ZnCl2 and potassium hexacyanocobaltate(III) solution, in presence of the organic ligand (tBuOH), confirmed that a significant part of the catalyst material reveals the features of the non-crystalline structure. Extended X-ray absorption fine structure (EXAFS) analysis established that only Zn atoms are the active metallic centers in the DMC catalyst. The coordination around Zn was changed from octahedral in reference material to tetrahedral in catalysts, and Cl atoms were detected near some of the Zn atoms, but no significant amount of oxygen atoms was detected, which agrees with XPS chemical analysis. The performed experimental studies give direct experimental evidence for the model deduced by Zhang et al., and for the calculation performed by Wojdel et al. Moreover, the generally accepted formula Zn3[Co(CN)6]2•xZnCl2•ytBuOH•zH2O describing this catalyst is not valid, because none of the compounds were detected by XRD or EXAFS techniques. Regarding the relation between structural and chemical activity of catalyst, we conclude that for the chemical activity of DMC catalyst not only is the content of Cl very important, but also the fraction of non-crystalline phase, the formation of which is stimulated by ligand. The non-crystalline fraction of catalyst may offer the easier access to the active center with Cl. Copyright © 2015 John Wiley & Sons, Ltd.

Advanced electronic devices based on III-N semiconductors, particularly these operated at the high power and high frequency or corrosive atmosphere, need elaboration of new technology for contacts metallization which are thermally and chemically stable. Performed studies aimed at the development of materials for applications in the improved metallization. Due to the unique combination of the metallic electro-thermal conductivity and ceramic resistance to oxidation and thermal stability, the MAX phases were chosen as the materials potentially applicable to this task. Particular interest lies in the MAX phases based on the Ti, Si and C or N atoms, especially on the Ti 3 SiC 2 phase. The paper focuses on a comprehensive characterization of films grown by means of high-temperature magnetron Ti, Si and C co-sputtering. The complementary characterization by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) is presented. XRD studies pointed out the presence of several phases in the investigated samples, therefore XAS as an atomic sensitive probe was applied to examine the average atomic order around Ti atoms as a function of the technological parameters and to point towards proper procedures to achieve the appropriate stoichiometry around Ti atoms and finally the Ti 3 SiC 2 phase.

Ilmenite is a valuable source of titanium and is applied as the main raw material in the technology of titanium white pigment production. Ilmenite is found in many places in the earth, and its elemental as well as phase compositions very strongly depend on the place of origin. Deposits located in Australia, China, India, and Norway in Europe are well known places where ilmenites are exploited industrially. Main phases that were identified in these ilmenites are ilmenite FeTiO3, hematite Fe2O3, geikielite MgTiO3 and pseudorutile Fe2Ti3O9. Enstatite MgSiO3, MnTiO3, and kleberite (determined also as hydroxylian pseudorutile with approximate formula FeTi3O6(OH)3) are minor phases present in ilmenites. Calorimetric investigations of reactions of these ilmenites with sulphuric acid in standard conditions demonstrated significant differences in the shape of temperature and thermal power curves. On the basis of these investigations, it can be concluded that the shape of the thermal power curve is different for each of ilmenite and can be treated as a fingerprint of their phase composite.

The implantation of Mn ions into two Si substrates with different doping (P or B), resistivity and oxygen content was performed at low and high substrate temperatures. Different post-implantation p ...

The electronic structure of InGaN epitaxial layers grown on sapphire substrates was studied using X-ray absorption at the In L3 and N K edges, as well as N Kα X-ray emission. Knowing that the InGaN crystallizes in an anisotropic wurtzite structure, the linear polarization of synchrotron radiation was exploited to estimate the influence of the crystal structure anisotropy on the distribution of the local density of states at the site of In and N. The calculated partial density of states describes the observed anisotropy in the measured spectra. Influence of the core–hole effect on the analyzed absorption spectra was verified and reveal that a core hole potential is effectively screened by the surface mobile electrons for the sample with maximum indium content. The bandgap values were provided for the investigated InGaN alloys and were found to vary preudo-lineary with indium content.

We present X-ray absorption spectroscopy (XAS) and resonance inelastic X-ray scattering (RIXS) measurements of CdO thin film. The observed differences between bulk and surface XAS signals suggest the presence of a surface electron accumulation layer in CdO film. The native defects (oxygen vacancies) strongly influence on the electronic structure of CdO resulting in the absorption threshold position/onset and spectral profile changes. To interpret the obtained data ab initio theoretical calculations, using the FEFF code, were performed and compared to the experimental results. The calculated angular-momentum-projected local density of states (PDOS) describes well the experimental data. The direct and indirect gaps of CdO were estimated to be ∼2.4 eV and ∼0.9 eV, respectively, by overlapping the XAS spectrum with RIXS. These results are consistent with our optical absorption measurements as well as theoretical and experimental band gap values of CdO reported in the literature.

The local atomic structure around the central iron of the synthetic soluble analog of malarial pigment in acetic acid solution and with addition of chloroquine as found by X-ray absorption spectroscopy is reported. The special interest was drawn to the axial linkage between the central iron atom of the ferriprotoporphyrin IX (FePPIX) coordinated axially to the propionate group of the adjacent FePPIX. This kind of bonding is typical for hematin anhydride. Detailed analysis revealed differences in oxygen coordination sphere (part of dimer linkage bond) between synthetic equivalent of hemozoin in the powder state and dissolved in acetic acid and water at different concentrations mimicking the physiological condition of the parasite's food vacuole. The results of performed studies suggest that the molecular structure of synthetic analogue of hemozoin is no longer dimer-like in acidic solution. Further changes in atomic order around Fe are seen after addition of the antimalarial drug chloroquine.

The chemical bonding of Mn atoms in (Na1-xBix)(Nb1-yMny)O3 ceramics were analysed using the X-ray Absorption Near Edge Structure (XANES) measurement at the Mn L3,2–edge. In all the compounds coexistence of the covalent bonding MnCV state and ionic Mn+k states was found. The increase in the Bi and Mn content caused the marked dispersion and increased the values of electric conductivity and dielectric permittivity of the ceramics.

Chitosans represent a class of functional natural polymers. Their unique attribute is the capability to bind metal ions into their structure. This property can be exploited in many biomedical applications, but before that, some questions about metal binding mechanism must be answered. O-carboxymethyl chitosans with accumulated Fe atoms were studied by X-ray absorption spectroscopy. It was shown that iron bonding depends on the technological processes used in chitosan production. The applied technology allows for the selective introduction of either oxygen alone or of nitrogen and oxygen into the nearest neighbourhood of Fe. Therefore, it is possible to control the surroundings of a metal atom depending on requirements.

X-ray absorption spectroscopy is used to determine the local atomic structure around the iron atom from a soluble synthetic analogue of malaria pigment (hemozoin), cf. ferrimesoporphyrin IX of mesohematin anhydride, in the absence or presence of chloroquine (CQ) in dimethyl sulfoxide (DMSO). Of particular note are the CQ-induced changes in the structure of mesohematin anhydride, which might confirm the formation of CQ-ferrimesoporphyrin IX complex. Examination of solutions of mesohematin anhydride dissolved in DMSO reveals preservation of the dimerlike structure with the central iron atoms of the ferric porphyrin IX reciprocally linked by propionate side chains, which is typical for hematin anhydride (β-hematin). In the presence of CQ, additional light atoms, such as nitrogen, carbon, and oxygen, were detected surrounding the iron in a distance ranging from 2.48 to 3.77 Å. The changes introduced by CQ in DMSO are different from that observed in the acetic acid solution.

Natural ilmenites are used all over the world as raw materials in white pigment (TiO 2 ) production. Besides the FeTiO 3 in the raw material many other compounds are present. The chemical compounds based on the minority elements influence quality of the final product and are difficult to identify. The knowledge about chemical bonding of the minor elements enables to properly adjust chemical reactions during production processes and to improve quality of the final product. In this paper the X-ray absorption spectroscopy (XAS) identification of the chemical compounds formed by Mg, Mn and Cr in natural ilmenites originating from different places is presented.

The local atomic structure around iron atoms of two synthetic analogues of malarial pigment product is characterized by iron K-edge X-ray absorption fine structure spectroscopy (XAFS). Malarial pigment, also termed hemozoin, is a condensed phase of ferriprotoporphyrin-IX dimers, and is structurally identical to the synthetic material hematin anhydride, which is also termed IS-hematin. Synthetic hemozoin analogues might serve as surrogates or models of malaria pigment for a range of fundamental laboratory methods, for example the design of new antimalarials. Two new iron(III)(protoporphyrin-IX) analogues, based on meso- and deuteroporphyrin are considered. Both new condensed phases are slightly soluble in many organic solvents. In the present work, the detailed examination of X-ray absorption spectra of monomer- and dimer-ferriprotoporphyrin-IX-based compounds is discussed. Parameters obtained by quantitative spectra analysis allow us to classify the new synthetic equivalents of the parasite product as dimer materials. X-ray absorption technique was able to distinguish dimer from monomer structures based on the structural disorder parameters of oxygen ligand bonding. (C) 2010 Elsevier B.V. All rights reserved.

Although Ta2O5 is thermodynamically the most stable form of TaxOy, the chemical composition/stoichiometry of TaxOy films may generally be complex. On the other hand, to be robust in harsh chemical environments, the film material is required to be amorphous rather than crystalline. The amorphousness of atomic layer deposited (ALD) films is promoted by low process temperature generally. This paper presents the study on TaxOy films deposited by ALD at low temperature (100 °C) using TaCl5 and H2O as chemical precursors, bringing the compositional, structural, and optical properties of the films together. The films with the thickness in the range of 32–202.5 nm were deposited mostly on Si (100) wafers. For their characterization, secondary ion mass spectroscopy, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, x-ray diffractometry, and spectroscopic ellipsometry were performed. The films were overstoichiometric in relation to Ta2O5, with the O/Ta ratio in the range of 2.7–2.8. Addition...

The interesting chemical and physical properties of Mn-oxide-based nanomaterials offer a variety of technological applications. The novel Mn-oxide properties reached through synthetic design have the potential to be of tremendous contribution to modern, environmental friendly chemistry. A problem of Mn oxide crystal chemistry is that, even within a single mineral, Mn atoms can exhibit multiple valence states. An average oxidation state for Mn atoms can be easily and quite reasonably measured, however, determining the individual proportions/(“weights”) of Mn(IV), Mn(III), and Mn(II) in a non-destructive way is considerably more difficult. We applied X-ray absorption near edge spectroscopy (XANES) to investigate the Mn environment and to improve fundamental understanding of the structural chemistry and morphology of nanostructured Mn-oxides to produce desirable chemical and physical properties.

A Si (1 0 0) crystal implanted with Mn + ions, exhibiting ferromagnetic properties, was studied with XAS and TEM to examine the local atomic order around Mn atoms. The advantage of the XAS technique was its elemental selectivity, which allowed extracting information on the atomic surroundings of Mn atoms even at very low concentrations of this element, incapable of producing a signal in X-ray diffraction. It is very important to find out what is responsible for the ferromagnetism of this new class of materials. The knowledge of the location of Mn atoms in the Si crystal lattice is crucial in developing models of ferromagnetic interactions. The performed studies have proven beyond doubt that Mn atoms are not located randomly in the Si crystalline matrix but form Mn–Si clusters immersed in a strained Si matrix. Assuming the atomic order and dimensions of the cluster found through EXAFS and HRTEM, we have reproduced the electronic structure of Mn atoms by modeling the XANES spectrum in agreement with the experimental one.

X-ray absorption near edge structure (XANES) spectra of Ti, Si, B and N K-edges were investigated to determine the phase composition of multicompounds cubic boron nitride (cBN) based composites formed by reaction of cBN with Ti 3 SiC 2 ceramics. Knowing that the shape of XANES spectra is a fingerprint of chemical bonding of the element in compound, a linear combination of XANES spectra of reference compounds (phases) was fitted to the spectra of the composites. This procedure permitted to determine the fraction of the componential phases in studied materials. X-ray Diffraction (XRD) analysis confirmed the presence of compounds detected by XANES analysis. The similarities and differences between XANES and XRD results are discussed. The combination of XANES and XRD techniques allowed to estimate the quantity of presented compounds within the limits of sensitivity of each method.

X-ray absorption methods have been successfully used to obtain quantitative information about local atomic composition of two different materials. X-ray Absorption Near Edge Structure analysis and X-Ray Photoelectron Spectroscopy allowed us to determine seven chemical compounds and their concentrations in c-BN composite. Use of Extended X-ray Absorption Fine Structure in combination with Transmission Electron Microscopy enabled us to determine the composition and size of buried Ge quantum dots. It was found that the quantum dots consisted out of pure Ge core covered by 1-2 monolayers of a layer rich in Si.

The X-ray absorption spectroscopy was applied for analyzing the positions of atoms in hemozoin and reference sample of β-hematin. The XANES and EXAFS of iron K-edges were measured for the malarial pigment, hemozoin (a product of the intraerythrocytic phase of Plasmodium parasite causing malaria disease) and its synthetic homologue, β-hematin. The results were analyzed and discussed in relation to the crystallographic model of β-hematin.

Analysis of Ge K-edge extended X-ray absorption fine structure (EXAFS) of strained and relaxed germanium quantum dots (QDs) in “sandwich” Si/Ge/Si structures, is reported. The QDs were formed in germanium monolayers (ML) grown with different thickness at the very low temperature (210 °C). The presence of Si cap on the Ge ML induces additional stresses and modifies the shape and composition of formed structures. Formation of monocrystal Ge core inside the QDs is suggested on the basis of the results of fitting and from the estimation of contribution of Si atoms from the QDs surface. The reduction of Ge layer growth temperature to 210 °C limits the Si interdiffusion inside the QDs.

Theoretical and experimental studies of cubic BN mixed with Ti and TiN in the molar ratio 1:1 are reported and compared with the properties of Ti and TiN films grown by the arc plasma deposition method on cBN substrate. Theoretical calculations show that Ti and TiN react with cubic BN forming new phases at 1000 and 1400 °C. The cBN composites were prepared by high pressure hot pressing and the samples were subsequently annealed at 1000 and 1400 °C. The samples after heat treatment were characterized using transmission electron microscopy (TEM). The X-ray absorption technique and X-ray photoelectron spectroscopy (XPS) were used to study the content of new phases formed in the cBN–Ti/TiN samples. The measurements of micro-hardness showed the significant differences in mechanical properties of samples. The amount and distribution of TiB 2 phase in cBN–Ti/TiN composites are shown to be determining factors for the micro-hardness.

In spite of great interest of industry in titanium composites based on the cubic boron nitride (c-BN), there is a lack of information about the chemical binding of Ti in these materials. The reason for that are difficulties in characterizing the multiphase materials with high hardness using conventional methods. In the present paper, to estimate the content of different compounds of Ti formed during the technological processes we used element selective-spectroscopy. The X-ray absorption near-edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) were chosen to estimate the amount and kind of compounds formed. The performed analysis proved the existence of several Ti compounds (TiC, TiB 2 , TiSi 2 , TiO 2 , Ti 3 SiC 2 , TiC 0.7 N 0.3 , TiC 0.3 N 0.7 ) and allowed to evaluate the percent of Ti bounded to each compound. Additionally, the X-ray diffraction (XRD) measurements were performed on the same samples. Due to the existence of several compounds with similar crystal structures and the high hardness of samples, the quantitative-phase analysis was not possible by XRD. Therefore, XANES and XPS appear to be the perfect tools for the investigation of micro-chemical processes occurring in composites.

X-ray photoelectron spectroscopy (XPS) is used to estimate phase and element contents of the composites based on cubic boron nitride. A composite is a mixture of several compounds and the use of traditional X-ray diffraction for phase analysis in many cases can be difficult. By using XPS, we were able to evaluate the atomic concentration of elements and the content of different compounds of each element. SEM and XPS showed that samples are heterogeneous. The TiB2 phase, expecting from thermodynamic calculations, was formed in both investigated samples of cBN/Ti3SiC2/TiC but in different amount. The Ti3SiC2 additive was found more chemically active then TiC.

The local structure of Si-capped Ge quantum dots formed in Stranski–Krastanov growth mode on a (001) Si substrate was probed by X-ray absorption at the Ge K-edge. Analysis by extended X-ray absorption fine structure (EXAFS) was performed under the assumption of a solid solution model of the Si distribution inside the quantum dots (QDs) and taking into account polarization effects. It was found that QDs formed for 8 ML are strained and the Ge–Ge and Ge–Si bond lengths vary with direction. The Si content inside the QDs was found to be at a level of ∼25 at.% for strained (8 ML sample) QDs and ∼12 at.% for unstrained (10 ML sample) QDs. This work demonstrates the usefulness of EXAFS analysis for the determination of the local atomic structure in covered low-dimensional structures.

We report on the use of X-ray absorption spectroscopy as a tool for the identification of the phases formed in the technological process of composite preparation. A composite is a mixture of several compounds and, in many cases, the use of traditional X-ray diffraction to determine the phases can be difficult because of the small amount of phases present. X-ray absorption studies (XANES and EXAFS) of the c-BN Ti/TiN layered system are presented. These materials are models of the powdered composites used in industry for tool production. XANES and EXAFS analyses showed that, after annealing up to 1300 °C, a TiB 2 phase is formed, but the chemical bonding of the Ti atoms differs slightly from that of standard TiB 2 powder, showing the presence of defects in site occupancy. Assuming that the X-ray absorption spectral shape is a linear combination of the spectra of all the components, we estimated the kind and limits of other phase inclusions.

The electronic structures of ordered Ni 3 Al 1− x Mn x alloy were calculated using the ab inito self-consistent linear muffin-tin orbital (LMTO) method with the local density approximation. Two models of the site occupancy in the elemental f.c.c. cell were considered: (A) Mn atoms substituting the Al atoms located at the corners of the f.c.c. cube; (B) Mn atoms substituting the Ni atoms located at the faces of the cube while maintaining the appropriate number of Ni atoms at the cube corners. LMTO-atomic spherical potential approximation calculations were performed for x =0, 0.25, 0.50, 075, 1.0 and compared with measured X-ray absorption spectra. The influence of manganese atoms location in the f.c.c. lattice on the density of state (DOS) shapes was discussed. The performed studies indicate that it is more features in the DOS resulting from the second model of Mn substitution that find confirmation in the X-ray absorption spectra.