Neodymium and Erbium Coordination Environments in Phosphate Glasses

The local structures of Nd3+ and Er3+ ions in two series of rare-earth (RE) phosphate glasses with nominal compositions xR203-(1-x)P2O5, where R=Nd and Er and 0.05≤x≤0.28, have been characterized by LIII-edge extended x-ray-absorption fine-structure spectroscopy (EXAFS). The RE coordination number depends on the R2O3 content, decreasing from 9.0 (10) oxygen nearest neighbors in ultraphosphate compositions (x\u3c0.15) to 6.4 (9) oxygen nearest neighbors for the metaphosphate (x∼0.25) compositions. The average Er-O bond distance decreases from 2.29 (1) to 2.23 (1) Å, and the average Nd-O bond distance decreases from 2.40 (1) to 2.37 (1) Å over the same compositional range. The changes in coordination environments are consistent with the conversion of isolated RE polyhedra to clustered RE polyhedra sharing common oxygens as the number of available terminal oxygens per RE ion decreases with increasing x

Electronic properties of hybrid organic/inorganic semiconductor pn-junctions

Hybrid inorganic/organic semiconductor heterojunctions are candidates to expand the scope of purely organic or inorganic junctions in electronic and optoelectronic devices. Comprehensive understanding of bulk and interface doping on the junction’s electronic properties is therefore desirable. In this work, we elucidate the energy level alignment and its mechanisms at a prototypical hybrid pn-junction comprising ZnO (n-type) and p-doped N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (α-NPD) as semiconductors, using photoelectron spectroscopy. The level alignment can be quantitatively described by the interplay of contact-induced band and energy level bending in the inorganic and organic component away from the interface, and an interface dipole due to the push-back effect. By adjusting the dopant concentration in α-NPD, the position of the frontier energy levels of ZnO can be varied by over 0.5 eV and that of α-NPD by over 1 eV. The tunability of this pn-junction’s energy levels evidences the substantial potential of the hybrid approach for enhancing device functionality.Deutsche Forschungsgemeinschafthttps://doi.org/10.13039/501100001659Peer Reviewe

A new highly automated sputter equipment for in situ investigation of deposition processes with synchrotron radiation

8 pags., 7 figs., 1 tab.HASE (Highly Automated Sputter Equipment) is a new mobile setup developed to investigate deposition processes with synchrotron radiation. HASE is based on an ultra-high vacuum sputter deposition chamber equipped with an in-vacuum sample pick-and-place robot. This enables a fast and reliable sample change without breaking the vacuum conditions and helps to save valuable measurement time, which is required for experiments at synchrotron sources like PETRA III at DESY. An advantageous arrangement of several sputter guns, mounted on a rotative flange, gives the possibility to sputter under different deposition angles or to sputter different materials on the same substrate. The chamber is also equipped with a modular sample stage, which allows for the integration of different sample environments, such as a sample heating and cooling device. The design of HASE is unique in the flexibility. The combination of several different sputtering methods like standard deposition, glancing angle deposition, and high pressure sputter deposition combined with heating and cooling possibilities of the sample, the large exit windows, and the degree of automation facilitate many different grazing incidence X-ray scattering experiments, such as grazing incidence small and wide angle X-ray scattering, in one setup. In this paper we describe in detail the design and the performance of the new equipment and present the installation of the HASE apparatus at the Micro and Nano focus X-ray Scattering beamline (MiNaXS) at PETRA III. Furthermore, we describe the measurement options and present some selected results. The HASE setup has been successfully commissioned and is now available for users.We would like to thank Dimitri Novikov (DESY) and Carsten Richter (DESY, TU Freiberg) for their help concerning the reflectivity measurements and the fits of the XRR measurements, as well as Reinhard Eisenberg (DESY) for the preparation of the video film.Peer reviewe

Formation of Al nanostructures on Alq3: An in situ grazing incidence small angle X-ray scattering study during radio frequency sputter deposition

6 pags., 4 figs., 1 sch.The formation of metal/organic interfaces is a complicated process involving chemical interaction, physical nucleation and diffusion, and thin film growth. It is closely related to the performance of organic electronic devices. To understand this process, we investigate the system of aluminum (Al) and tris(8-hydroxyquinolinato)aluminum (Alq3) as a model, owing to the well-known strong chemical interaction between both and their close technological relevance to organic light emitting devices. By using grazing small angle incidence X-ray scattering (GISAXS), we follow the Al thin film development on top of Alq3 during radio frequency (rf) sputter deposition in real-time and without interrupting the growth process. Three growth stages have been clearly distinguished: Al diffusion into Alq3, Al/Alq3 complex agglomeration and self-assembled Al pillar nanostructure thin film development. Thus in situ GISAXS yields the fundamental insights into the formation of the metal/organic interface for small organic semiconductor devices, prepared via vacuum based deposition techniques. © 2013 American Chemical Society.S.Y. acknowledges the Knut och Alice Wallenberg foundation for the kindfinancial support. P.M.-B., E.M., and K.S.acknowledge financial support by TUM.solar in the frame ofthe Bavarian Collaborative Research Project“Solar technologiesgo Hybrid′′(SolTec) and by the GreenTech Initiative(Interface Science for Photovoltaics - ISPV) of the EuroTechUniversities. Portions of this research were carried out at thelight source PETRA III at DESY, a member of the Helmholtz Association (HGF). Dr. David Babonneau is acknowledged forhelpful discussion, and Erik Braden for the XRR measurementsPeer reviewe

Modifier Effects on the Properties and Structures of Aluminophosphate Glasses

Properties and structures of potassium, barium and magnesium alumino-metaphosphate glasses (O/P≈3) have been investigated. Adding Al(PO3)3 to an alkali or alkaline earth metaphosphate glass improves the chemical durability, increases the glass transition temperature and reduces thermal expansion and residual OH-content. Infrared spectra are dominated by metaphosphate vibrational modes, the frequencies of which are dependent on the field strengths of the modifying cations. 27Al MAS NMR spectroscopy indicates that aluminum ions are incorporated into the aluminophosphate network primarily in octahedral sites, although tetrahedral and pentahedral sites are also present. The average aluminum co-ordination number decreases in the series K+\u3eBa2+\u3eMg2+ and this is related to a reduction in the basicity of glasses with higher field strength modifiers. © 2001 Published by Elservier Science B.V

Structure and Properties of Lanthanum-Aluminum-Phosphate Glasses

Glass-forming characteristics, properties and structural features of glasses in the La2O3-Al2O3-P2 O5 system have been investigated. The glass-forming region is small compared to the Na2O-Al2O3-P2O5 system. Glass transition temperature increases and thermal expansion coefficient, refractive index, and density all decrease as the alumina content of the glass is increased. Infrared (IR) spectroscopy indicates that the glass network is dominated by bridging P-tetrahedra with terminal tetrahedra present in glasses with O/P ratios \u3e 3. 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy indicates that Al ions are incorporated in these glasses in 4-, 5-, and 6-coordinated sites. The average Al-coordination number (CN) increases with an increase in the Al/La ratio and decreases with an increase in the O/P ratio. Both trends can be explained by the avoidance of Al-O-Al bonds in the glass structure. © 2001 Elsevier Science B.V

Cation Effects on Anion Distributions in Aluminophosphate Glasses

Alkali aluminophosphate glasses, including those in the system xAl2O3·(1-x)CsPO3 (0 ≤ x ≤ 0.25), were examined by high-performance liquid chromatography (HPLC), infrared (IR), and 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies. Phosphate anions become progressively shorter with the addition of alumina to a metaphosphate glass. Al3+ ions are initially incorporated into the structure in octahedral sites, but the average Al coordination number (CN) decreases with increasing alumina content and tetrahedral species are the preferred moiety when [O]/[P] \u3e 3.5. Al[4] sites appear to be associated with monophosphate (Q0) anions. The role of modifier size on aluminophosphate structure is investigated. At low alumina content (\u3c 15 mol%), the disproportionation of pyrophosphate anions into triphosphate and orthophosphate anions is responsible for the lower average Al CN of cesium aluminophosphate glasses compared with sodium aluminophosphate glasses

High-energy X-ray Diffraction Study of La Co-ordination in Lanthanum Phosphate Glasses

Differences in La co-ordination environments indicated in the structures of rare earth-phosphate crystals in glasses with compositions ranging from ultraphosphate to metaphosphate stoichiometries were investigated. A series of lanthanum phosphate glasses were characterized by X-ray diffraction analysis and a change of the La-O co-ordination number was extracted by Gaussian fitting of the first-neighbor distances. The decrease in co-ordination number was due to the transition of ultraphosphate glass structures to metaphosphate structures. The changes in the La environments explained the compositional dependence of glass properties

In Operando Small-Angle Neutron Scattering Study of Single-Ion Copolymer Electrolyte for Li-Metal Batteries

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