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The synthesis, characterisation and crystal structure of a novel U5+ (dominant) brannerite of composition U1.09(6)Ti1.29(3)Al0.71(3)O6 is reported, as determined from Rietveld analysis of high resolution powder neutron diffraction data. Examination of the UTi2-xAlxO6 system demonstrated the formation of brannerite structured compounds with varying Al3+ and U5+ content, from U0.93(6)Ti1.64(3)Al0.36(3)O6 to U0.89(6)Ti1.00(3)Al1.00(3)O6. Substitution of Al3+for Ti4+, with U5+ charge compensation, resulted in near-linear changes in the b and c unit cell parameters and the overall unit cell volume, as expected from ionic radii considerations. The presence of U5+ as the dominant oxidation state in near single phase brannerite compositions was evidenced by complementary laboratory U L3 edge and high energy resolution fluorescence detected (HERFD) U M4 edge X-ray Absorption Near Edge Spectroscopy. No brannerite phase was found for compositions with Al3+ / Ti4+ > 1, which would require U6+ contribution for charge compensation. These data expand the crystal chemistry of uranium brannerites to the stabilisation of dominant U5+ brannerites by substitution of trivalent cations, such as Al3+, on the Ti4+ site

Implantation and subsequent behaviour of heavy noble gases (Ar, Kr, Xe) in few-layer graphene sheets and in nanodiamonds is studied both using computational methods and experimentally using X-ray absorption spectroscopy. For the first time the Xe-vacancy (Xe-V) defect is experimentally confirmed as a main site for Xe in the diamond. It is shown that noble gases in thin graphene stacks distort the layers, forming bulges. The energy of an ion placed in between flat graphene sheets is notably lower than in domains with high curvature. However, if the ion is trapped in the curved domain, considerable additional energy is required to displace it.

The key to fabricate complex, hierarchical materials is the control of chemical reactions at various length scales. The classical model of nucleation and growth fails to provide sufficient information. Here, we illustrate how modern X-ray spectroscopic and scattering in situ studies bridge the molecular- and macro- length scales for an assembly of CoO polyhedral shape nanocrystals. By combining high energy-resolution fluorescence-detected X-ray absorption near edge structure (HERFD-XANES) measurements and FEFF simulation, we directly access the molecular level of the reaction. We reveal that initially Co(acac)3 rapidly reduces to Co(acac)2 and coordinates to oxygen atoms of two solvent molecules, forming a bis-adduct of the square-planar Co(acac)2 with octahedral coordination. Unlike a classical nucleation and growth mechanism, we observe that nuclie as small as 2 nm assemble into superstructures of 20 nm. The individual nanoparticles and assemblies continue growing at a similar pace. The final assemblies are smaller than 100 nm and maintain their spherical shape, while the nanoparticles reach a size of 6 nm and adopt various polyhedral, edgy shapes. Our work thus provides a comprehensive perspective on the emergence of nano-assemblies in solution

Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P43n(a,0,0)000(0,a,0)000(0,0,a)000; a = 8:72328(1) Å, Q1 = Q2 = Q3 = 0:4974(2)] modulated crystal structure. A slight shift of the composition towards higher Ybcontent (i:e: Yb3:2Co4Ge12:8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pm3n, a = 8:74072(2) Å] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature dependent intermediate valence state of +2:60+2:66 for the temperature range 85-293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements

The 5f -based ferromagnet UGa2 with the Curie temperature TC = 125K was investigated by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) experiments at the U–M4,5 and Ga–K edges. The position of the U–M4 white line, determined in the high-energy resolution fluorescence detection XAS, suggests that UGa2 is neither a localized 5f 2 nor an itinerant system with 5f occupancy close to n5f = 3. The analysis of the acquired M4,5XANES and XMCD spectra indicates the 5f occupancy close to 2.5 and a large orbital magnetic moment of the uranium 5f states (3.18 μB) that is partly compensated by the antiparallel spin moment (1.31 μB). Thus, the total 5f magnetic moment of 1.87 μB is obtained, which is smaller than the known bulk magnetization of 3.0 μB per formula unit, while the magnetic moments of the Ga atoms are negligible. Several methods based on density-functional theory were applied and the obtained results were compared with XAS spectral features, the Sommerfeld coefficient of the electronic specific heat, and the size of the U moments and 5f occupancies. A clear correlation is revealed between the U–M4 white-line position of three metallic uranium compounds and the calculated uranium ionicity. It is demonstrated that only electronic structure methods taking appropriate care of orbital magnetism and related atomic multiplet effects can successfully describe all considered properties

The distortion of the atomic structure around In and Cu atoms in sphalerite ZnS was explored by reverse Monte Carlo (RMC) method applied to the Extended x-ray absorption fine structure (EXAFS) interpretation. Parameters of the local atomic structure (interatomic distances) around dopants in synthetic In- and In-Cu-bearing sphalerites were determined by fitting In and Cu K-edge EXAFS spectra using evolutionary algorithm (EA) of the RMC method. These data were complemented with quantum chemical Density Functional Theory (DFT) calculations and theoretical modeling of XANES spectra. The RMC-EXAFS method showed that the three coordination shells of In-bearing sphalerite are characterized by almost symmetrical Gaussian type peaks, which shapes are close to the one of pure sphalerite. This shape of the peaks is characteristic of symmetrical undisturbed structural environment of In in the sphalerite solid solution which is formed via the charge compensation schemes 3Zn2+↔2In3++□, where □ is a Zn vacancy. However, in case of (In,Cu)-bearing sphalerites formation of solid solution state follows the charge compensation scheme 2Zn2+↔Cu++In3+. In this case some splitting of the RDF peaks are observed, the splitting rate correlates with impurities concentrations. In contrast to In, the local atomic structure around Cu is not symmetric. The 2nd coordination shell around Cu (which consists of 12 metal atoms) can be described by three distinct Gaussian contributions. This splitting of interatomic distances in the 2nd coordination shell points out on the significant distortion of the ZnS crystal structure around Cu. The theoretical calculation of Cu K-edge XANES based on the distorted structural environment near Cu provides better agreement with the experiment than the symmetrical atomic model. According to our DFT calculations, considerable splitting of the 2nd coordination shell (up to 0.1 Å for Cu) occurs in the case of close positions of the impurity atoms or the Zn vacancy. The DFT calculations showed that the geometries with the close arrangement (clustering) of the impurities – In and Cu atoms, or the In atom and a vacancy, are energetically more favorable than the random distribution of the defects. However, as no heavy In atoms were detected in the 2nd shell of Cu, and the 2nd shell of In is almost undisturbed, we conclude that the defects are distributed randomly (or at least not close to each other). The disagreement of RMC-EXAFS fittings with results of DFT calculations, according to which the closest arrangement of dopants is the most stable configuration, can be explained by the presence of other defects of the sphalerite crystal lattice which were not considered in the DFT calculations.

Processing of Zn ore accounts for >95% of production of In - a "critical" metal which is widely used in the high-tech electronics. The main source of In is sphalerite (Zn, Fe)S which also can host industrial concentrations of Au. Here we use X-ray absorption spectroscopy to investigate the coupled chemistry of In and Au in synthetic sphalerite crystals - analogues of natural minerals. The concentrations of In and Au were found to correlate with each other and reached 0.5 wt% in crystals synthesized at 850 °C. Both metals are homogeneously distributed within the sphalerite matrix. However, their positions within the mineral are different. In accord with X-ray absorption near edge structure (XANES) spectroscopy the formal oxidation state of these elements is +3 (In) and +1 (Au). Analysis of extended X-ray absorption fine structure (EXAFS) spectra revealed that In replaces Zn in the structure of sphalerite. The In-ligand distance increases by 0.12 Å and 0.09-0.10 Å for the 1st and 2nd coordination spheres, respectively, in comparison with pure ZnS. The In-S distance in the 3rd coordination sphere is close to the one of pure sphalerite. The In K-edge and Au L3-edge XANES and EXAFS spectra suggest that there is no In-Au clustering. Gold in sphalerite is coordinated with 2.5±0.3 S atoms at Au-S distance of 2.35±0.01 Å in the 1st coordination sphere, whereas distant coordination spheres have disordered nature. Our data suggest that at least two different forms of Au are present in sphalerite. At high Au concentrations (0.03-0.5 wt%) the nanosized Au2S clusters predominate, probably with small admixture of the Au solid solution characterized by higher Au-S distance. Alike Au, the other 1st group metals (Me) Cu and Ag, which often are present in high (tenths ppm to wt%) concentrations in sphalerite, can form nanosized Me-S clusters with only traces (ppm level) of metal in the solid solution state.

Hydrothermal chloride-rich fluids are identified at the late stages of the formation of platinum group element (PGE) deposits in giant layered intrusions, and are considered as the PGEs transport media in Cu(-Mo,Au) porphyry systems. In order to quantify the hydrothermal mobility of Pt we performed an investigation of the speciation of Pt in hydrothermal chloride-bearing fluids and dry melt by means of X-ray absorption spectroscopy (XAS). The experiments consisted in recording the Pt L-3-edge X-ray absorption near edge structure/extended X-ray absorption fine structure (XANES/EXAFS) spectra of Pt-bearing fluids obtained by dissolution of Pt metal in KCl/HCl and CsCl/HCl fluids in the temperature range from 450 to 575 degrees C at pressures from 0.5 to 5 kbar. A spectrum of Pt dissolved in dry CsCl/NaCl/KCl + K2S2O8 melt was recorded at 650 degrees C. The capillary method, when the experimental solution together with Pt((cr) )is sealed inside a silica glass capillary, was used. As was determined from the XANES spectra, in all the experimental systems Pt existed in the +2 oxidation state. Analysis of EXAFS spectra showed that Pt is coordinated by four Cl atoms with Rpt-cl = 2.31 +/- 0.01 angstrom independently of the T-P-compositional parameters. No evidence of the formation of complex with alkali metal cations in the second coordination sphere of Pt was found by the analysis of the EXAFS spectra of concentrated CsCl brines and melt. Our results imply that PtCl42- is the main Pt-Cl complex which predominates in hydrothermal fluids at t > 400 degrees C and fluid density d > 0.3 g.cm(-3). Experimental data obtained for dry melt of alkali metal chlorides suggest that Pt-Cl complexes can dominate Pt speciation in chloride-bearing aluminosilicate melts where Cl exhibits a salt-like atomic arrangement and ionic bonding. The literature data on the Pt solubility constant, Pt-(cr) + 2HCl((aq))degrees + 2Cl(-) = PtCl42- + H-2(aq), are compiled and fitted to the simple density model equation log K-s degrees (PtCl42- ) = 0.973 - 8202. T(K)(-1) - 5.505 . log d (w) + 2223 . log d(w) .T(K)(-1), where d(w) is the pure water density in g.cm(-3). The equation, combined with the extended Debye-Hiickel equation for activity coefficients, can be used to calculate the solubility of Pt up to 1000 degrees C/5 kbar. It accurately predicts the solubility of Pt in concentrated chloride brine (up to 50 wt% NaCl) at parameters of magmatic-hydrothermal transition (800 degrees C/1.4 kbar). At fluid/vapor density below 0.3 g.cm(-3) a neutral complex PtCl2 degrees((aq)) is suggested as the dominant Pt species. Our data demonstrate that Pt is highly mobile in high-temperature oxidized chloride-rich hydrothermal fluids. For example, at 800 degrees C/2 kbar the concentration of Pt can reach a few wt% in the 1 wt% HCl/50 wt% NaCl fluid which is in equilibrium with magnetite-hematite buffer. Once a Cl-reach fluid exsolves from alumuinosilicate melt, Pt follows Cl and enriches the fluid phase where it exists mostly in the form of PtCl42-. Decrease of temperature, acidity, and fluid chlorinity results in precipitation of Pt from the fluid phase.

Using X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure spectroscopy, atomic force microscopy, and Rutherford backscattering spectroscopy, the features of the microstructure and elemental composition of Si/GeMn magnetic systems obtained by molecular beam epitaxy and containing quantum dots are studied. Intense mixing of Ge and Si atoms is found in all samples. The degree of mixing (diffusion) correlates with the conditions of synthesis of Si/GeMn samples. For these systems, direct contacts of germanium atoms with manganese atoms are characterized and the presence of interstitial manganese with tetrahedral coordination and substitution of manganese for germanium and silicon in the lattice sites is found. The presence of stoichiometric phases Ge8Mn11, Ge3Mn5 is not detected. The correlations of the Ge, Si, and Mn coordination numbers in the Ge environment are determined both with the Mn flux value (evaporator temperature) and with the temperature at which quantum dots are grown, as well as with other synthesis conditions. The manganese concentration in the samples is determined.

Chloride-bearing fluids are widespread in the Earth's interior from low-temperature subsurface conditions to deep lithosphere. The concentration of chloride salts varies from diluted aqueous solutions to concentrated brines and anhydrous (dry) chloride melts beneath volcanoes. Here we report an investigation of the state of Au in hydrothermal chloride fluids and anhydrous melts by means of in situ X-ray absorption spectroscopy combined with ab initio molecular dynamics simulations and thermodynamic modeling. The experiments included registration of Au L 3 -edge X-ray absorption near edge structure/extended X-ray absorption fine structure spectra of Au-bearing fluids in the temperature range from 350 to 575 °C at pressures of 150-4500 bar. Spectra of Au dissolved in dry CsCl/NaCl/KCl + K 2 S 2 O 8 melt were recorded at 650 °C. It was found that Au is coordinated by two Cl atoms (R Au-Cl = 2.25-2.28 Å). The alkali metal atoms (Me) were detected in the distant coordination sphere of Au at R Au-Me = 3.3-4.1 Å. The alkali metal cations in the vicinity of Au-Cl complex partly compensate the positive charge located on Au and, by this way, affect the Au-Cl distance. An increase of the fluid pressure causes expansion of the second coordination sphere composed of the alkali metal cations, which leads to the increase of the positive Au charge and results in slight contraction of the first coordination sphere of Au. Accordingly, the transport of Au in high-temperature chloride-bearing natural ore-forming fluids of moderate to high densities (>0.3 g·cm -3 ) can be explicitly described by the formation of the AuCl 2 - at any salt concentration from low-salinity fluids to hydrosaline liquids and anhydrous melts. In general, this means that the hydrothermal fluid chemistry simplifies with increasing temperature.

Developing characterization techniques and analysis methods adapted to the investigation of nanoparticles (NPs) is of fundamental importance considering the role of these materials in many fields of research. The study of actinide based NPs, despite their environmental relevance, is still underdeveloped compared to that of NPs based on stable and lighter elements. We present here an investigation of ThO2 NPs performed with High-Energy Resolution Fluorescence Detected (HERFD) X-ray Absorption Near-Edge Structure (XANES) and with ab initio XANES simulations. Structural models of ThO2 NPs with sharp edges and corners reproduce the size effect observed in experimental data. Inspection of the simulations from Th atoms in the core and on the surface of the NP indeed demonstrates that the origin of the effect is the lowering of the number of coordinating atoms for Th at the surface of the NP. The sensitivity of HERFD XANES to the less coordinated atoms at the surface may be exploited to investigate surface interactions.

Pyrite (FeS2) is a typical container of Pt in ores of magmatic and hydrothermal origin and in some carbonrich ores of sedimentary-diagenetic origin. Knowledge of the state of Pt disseminated in the matrix of pyrite, including local atomic environment (type of atoms in the nearest and distant coordination shells, coordination numbers, interatomic distances) and oxidation state, is necessary for physical-chemical modeling of platinum group element mineralization and for the improvement of Pt ore extraction and processing technologies. Here we report results of an investigation of local atomic structure of synthetic Pt-bearing pyrites by means of X-ray absorption spectroscopy (XAS). Synthesis experiments, performed at 580° and 590°C in a Pt-saturated system by means of salt-flux method, yielded crystals of pyrite with concentrations of Pt up to 4 wt %. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that the distribution of Pt within the pyrite grains is of zonal character, but within the distinct zones Pt is distributed homogeneously. Negative correlation between the concentrations of Pt and Fe was observed in the synthesized pyrite grains. The slope of the correlation line corresponds to the formation of the solid solution in the Pt-Fe-S system and/or to the formation of PtS2. The XAS experiments revealed the existence of two forms of Pt in pyrite. The main form is the solid solution Pt(IV), which isomorphically substitutes for Fe. The Pt-S distance in pyrite is ~0.1 Å longer than that of Fe-S in pure pyrite. The distortion of the pyrite crystal structure disappears at R >2.5 Å. The second Ptrich form was identified by means of high-resolution transmission electron microscopy (HRTEM) as nanosized inclusions of PtS2. Heating experiments with in situ registration of X-ray absorption spectra resulted in partial decomposition (dissolution) of PtS2 nanosized inclusions with the formation of the solid solution (Fe1–xPtx)S2. Therefore, the PtS2 nanosized particles can be considered as a quench product. Our data demonstrate that both Pt solid solution and PtS2 nanosized inclusions (at high Pt content) can exist in natural Pt-bearing pyrites.

The abandoned Krunkelbach uranium (U) mine, Southern Germany, with 2-3 km surrounding area represents a unique natural analogue site with accumulation of U minerals suitable for investigations of potential mobilization-immobilization processes expected in a real spent nuclear fuel repository. A specific feature of the site is the occurrence of more than forty secondary U minerals, from mixed redox U oxy-hydroxides to alkaline metal uranyl silicates, thus representing a wide scale of U ore weathering events. In this work the combination of synchrotron and laboratory techniques is used to unveil U speciation and micro heterogeneities in U phases accumulated on granitic rock outcrop from U deposit area. Available data on the age of the secondary U mineralization indicates that oxidizing processes at the site started some 340,000 years ago and continues up to date. Several phases close to Cu(UO2)2(PO4)2-x(AsO4)x·8H2O are identified on 1×2 mm2 area with presumably older, more evenly distributed Cu(UO2)2(SiO3OH)2·6H2O and (Fe, Ba, Pb)(UO2)2(WO4) (OH)4·12H2O, mineralization. Based on a multi-technique investigation 10-200 µm Cu(UO2)2(PO4)2-x(AsO4)x·8H2O particles with widely varying As-P content are analyzed. The evidences of a degradation occurred on some zones on the selected crystals are found associated with higher As and decreased P content. This observation can be apparently attributed to different degradation properties of the mixed As-P phases depending on As-P ratio and originate from different solubility properties of Cu(UO2)2(PO4)2·8H2O and Cu(UO2)2(AsO4)2·8H2O species. The conditions for preferential formation of As rich Cu(UO2)2(XO4)2·8H2O [X=As, P] phases and its possible role on U transport in environment under oxidizing conditions are discussed.

Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light harvesting applications due to their chemical stability, wide flexibility in composition, and recent increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced-dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory (DFT) calculations provide further details on the interaction and bandgap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can aid in establishing design principles for new, layered

Valence band electronic structure of mixed uranium oxides (UO2, U4O9, U3O7, U3O8, b-UO3) has been studied by the resonant inelastic X-ray scattering (RIXS) technique at the U M5 edge and by computational methods. We show here that the RIXS technique and recorded U 5f - O 2p charge transfer excitations can be used to proof the validity of theoretical approximations.

For nuclear fuel related applications, the oxygen stoichiometry of mixed oxides U1-yMyO2±x is an essential property as it af-fects the fuel properties and may endanger the safe operation of nuclear reactors. A careful review of the open literature indicates that this parameter is difficult to assess properly and that the nature of the defects, i.e. oxygen vacancies or UV, in aliovalent cation – doped UO2 is still subject to controversy. To confirm the formation of UV, we have investigated the room temperature stable U1-yLayO2±x phase using several experimental methods (e.g. XRD, XANES and NMR) confirmed by theo-retical calculations. This paper presents the experimental proof of UV and its effect we identified in both electronic and local structure. We observe that UV is formed in quasi equimolar proportion as LaIII in U1-yLayO2±x (y=0.06; 0.11; 0.22) solid solu-tions. The fluorite structure is maintained despite the cationic substitution but the local structure is affected as variations of the interatomic distances are found. Therefore, we provide here the definitive proof that the substitution of UIV with LaIII is not accommodated by the creation of O vacancies as has often been assumed. The UO2 fluorite structure compensates the incorporation of an aliovalent cation by the formation of UV in quasi equimolar proportions

Actinide nanomaterial research with cutting-edge effort in synthesis, processing and atomic-scale characterization is a fascinating and a rapidly progressing field of science. Experts around the world develop highly controllable synthesis approaches, use more sensitive characterization tools and finally improve models and theories to explain the experimental observations. This contribution will provide an overview of advanced X-ray spectroscopic techniques that take advantage of the resonant inelastic X-ray scattering (RIXS) in the hard and tender X-ray range and have become available for studying the electronic structure of actinides at the syn-chrotron facilities1–6. We will show latest results of actinide (hydroxo-) oxide nanoparticles stud-ies obtained by high-energy-resolution fluorescence detection (HERFD) X-ray absorption near edge structure (XANES) and RIXS spectroscopies (Fig.1.) at the U, Th and Pu L3 and M4,5 edges. The experiments were performed at the Rossendorf Beamline (ROBL) at the ESRF, where we recently installed a novel X-ray emission spectrometer7 with ground-breaking detection limit. We will show how the detail information about local and electronic structure of actinide nanomaterials can be obtained, including information on the electron-electron interactions, hybridization between molecular orbitals, the nature of their chemical bonding, and the occupation and the degree of the f-electron localization. The experimental spectral features have been analyzed using a number of theoretical methods. It might be of interest for fundamental research in chemistry and physics of actinide systems as well as for the applied science

We recently demonstrated a new low bandgap ferroelectric material based on BaTiO3. The co-doping of BaTiO3 exhibited robust spontaneous electrical polarization with bandgap values suitable for visible light absorption for application in optoelectronic devices. In this study, the valence and conduction bands are investigated with a combination of x-ray spectroscopies and DFT calculations. The local electronic structure and coordination of BaTi1-x(Mn1/2Nb1/2)xO3 is studied by means of x-ray absorption at the Ti K, Mn K, and O K edges. The spectroscopic evidence suggests only small distortions to the parent tetragonal ferroelectric system, reducing of the bandgap through compositional doping without compromising ferroelectricity to a large extent. The Ti K pre-edge features in particular, which are sensitive to site coordination and an indication of Ti off-centering within the Ti-O6 octahedra, shows modest changes with doping and strongly corroborates with our measured polarization values. Resonant photoemission spectroscopy results reveal newly created Mn d bands that hybridize with O 2p as well as additional valence band edge states with predominantly Mn d character. Through various x-ray spectroscopic techniques, we reveal the electronic structure that allows the compound to retain its ferroelectricity while reducing the bandgap

The electronic structure of AgxMo9Se11 as potential material for thermoelectric applications was studied using high-energy-resolution fkuorescence-detection x-ray absorption spectroscopy (HERFD-XAS) and resonant inelastic x-ray scattering (RIXS) technique. The experiments were supported by first-principle calculations using density functional theory (DFT). The analysis of obtained spectra indicate the presence of subvalent (less than 1+) Ag in the AgxMo9Se11. The advanced HERFDXAS measurements allowed us to resolve the contribution of the electronic states at the Fermi level of AgxMo9Se11 and monitor its dependence on the x value. Comparison of the experimental data with the results of the DFT calculations suggests an importance of the Ag2-type sites with the shortest Ag-Se distance for affecting the properties of AgxMo9Se11

The microstructures of amorphous and polycrystalline ferroelectric Hf0.5Zr0.5O2 films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film consists of an “incompletely mixed” solid solution of metallic oxides HfO2 and ZrO2. After rapid thermal annealing, the mixed Hf0.5Zr0.5O2 oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands form in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO2 and ZrO2. The presence of the HfO2 and ZrO2 phases in the Hf0.5Zr0.5O2 films is also detected by ellipsometry

X-ray photoelectron spectroscopy, EXAFS, XANES, spectral ellipsometry and quantum-chemistry calculations were used to examine the atomic and electronic structure of non-stoichiometric amorphous ZrOx slightly enriched with zirconium. The experimental data show that the ZrOx material consists of stoichiometric ZrO2, metallic Zr and zirconium suboxides ZrOy. The structure of ZrOx is analyzed using the Random Bonding and Random Mixture models. A model of nanoscale spatial potential fluctuations in ZrOx is substantiated. In this model, the potential fluctuations for electrons and holes arise due to the local fluctuations of bandgap energy in the range from 0 to 5.4 eV. A ZrOx-based flash memory element with giant retention time is proposed