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Abstract
Aqueous solutions of zirconium and hafnium (M) halides (X) with atomic ratios α = X/M near 1 form glasses on evaporation. Herein, we describe the preparation and properties of these glasses and discuss the nature of the crystal-glass equilibria beyond the pure glass compositions. Small- and wide-angle X-ray scattering (SWAXS) studies reveal increased polymerization as α decreases from 2 to 1. The glasses are found to be much denser than their crystalline counterparts. Crystals forming in contact with glasses retain the well-known Zr-tetrameric hydroxo cluster unit with hydroxide compensating for the lowered halide content. We find that the chemical formulas for all of the solid hydroxohalides may be described by the single parameter α, according to the formula M(OH)4-αXα·(4α - 1)H2O. This description is valid for the crystalline chloride (MOX2·8H2O = M(OH)2X2·7H2O), the glassy solids with α < 2, and hydrolyzed products (α ≈ 0.5). The water content is also determined by α with hydroxide-hydrogen bonding replacing halide-hydrogen bonding as α decreases. A Eu3+-doped Zr,Cl glass exhibits photoluminescence transitions 5D0 → 7Fn (n = 1, 2, and 4) of Eu3+, illustrating the asymmetric nature of the dopant sites in the glass.
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2
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Bonding and Tunneling. ACS OMEGA 2023; 8:23182-23190. [PMID: 37396288 PMCID: PMC10308573 DOI: 10.1021/acsomega.3c02736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 05/23/2023] [Indexed: 07/04/2023]
Abstract
Quantum mechanical electron tunneling is proposed as the mediator of chemical bonding. Covalent, ionic, and polar covalent bonds all rely on quantum mechanical tunneling, but the nature of tunneling differs for each bond type. Covalent bonding involves bidirectional tunneling across a symmetric energy barrier. Ionic bonding occurs by unidirectional tunneling from the cation to the anion across an asymmetric energy barrier. Polar covalent bonding is a more complicated type of bidirectional tunneling, consisting of both cation-to-anion and anion-to-cation tunneling across asymmetric energy barriers. Tunneling considerations suggest the possibility of another type of bond-denoted polar ionic-in which tunneling involves two electrons across asymmetric barriers.
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3
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Synthesis and Structural Analysis of Novel Phosphonium Hexatungstate Complexes. J CLUST SCI 2021. [DOI: 10.1007/s10876-020-01835-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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4
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High-Resolution Lithographic Patterning with Organotin Films: Role of CO 2 in Differential Dissolution Rates. ACS APPLIED MATERIALS & INTERFACES 2021; 13:18974-18983. [PMID: 33847481 DOI: 10.1021/acsami.0c21942] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Details of the chemistry enabling the patterning of organotin photoresists to single-digit-nm resolution continue to engage study. In this report, we examine the contributions of atmospheric gases to the differential dissolution rates of an n-butyltin oxide hydroxide photoresist. Cryo scanning tunneling electron microscopy (cryo-STEM) produces a micrograph of the latent image of an irradiated resist film, readily distinguishing exposed and unexposed regions. Temperature-programmed desorption mass spectrometry (TPD-MS) and cryo electron energy loss spectroscopy (cryo-EELS) show that irradiated films are depleted in carbon through desorption of butane and butene. Upon aging in air, irradiated films absorb H2O, as previously established. TPD-MS also reveals a previously unrecognized absorption of CO2, which correlates to a heightened dissolution contrast. This absorption may play an active role in determining intrinsic patterning performance and its variability based on changes in atmospheric-gas composition.
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Abstract
This work complements our recent discovery of new phases derived from zirconium perchlorate by addition of hydrogen peroxide. Here, we investigate analogous reactions with hafnium perchlorate, which is found to have modifications of the Clearfield-Vaughan tetramer (CVT). For hafnium perchlorate derivatives, we find distorted versions of CVT by X-ray diffraction and study the reaction solutions by SAXS, Raman spectroscopy, and ESI-MS. Furthermore, we investigate mixed Hf-Zr solution and solid phases and find the latter resemble the zirconium family at low Hf concentrations and the hafnium family at higher hafnium contents.
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Photoinduced Charge Transfer and Bimetallic Bond Dissociation of a Bi-W Complex in Solution. J Phys Chem Lett 2020; 11:7575-7582. [PMID: 32818381 DOI: 10.1021/acs.jpclett.0c02380] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Organometallic complexes including metal carbonyls have been widely utilized in academic and industrial settings for purposes ranging from teaching basic catalytic reactions to developing state-of-the-art electronic circuits. Characterization of these materials can be obtained via steady-state measurements; however, the intermediate photochemical events remain unclear, hindering effective and rational molecular engineering methods for new materials. We employed femtosecond transient absorption (fs-TA) and ground-state femtosecond stimulated Raman spectroscopy (FSRS) on triphenylbismuth-tungsten pentacarbonyl complex, a solution precursor for bimetallic oxide thin films. Upon 280 nm excitation into a charge-transfer band, an ultrafast bimetallic bond dissociation occurs within ∼140 fs. The subpicosecond nondiffusive solvation events are followed by ∼10 ps (15 ps) methanol (ethanol) complexation of the nascent tungsten pentacarbonyl intermediate, which mainly undergoes vibrational relaxation after crossing into a hot ground state. The trans ligand to axial CO is revealed to play a key role in the electronic and vibrational structure and dynamics of the complex. These findings could power rational design of bimetallic and functional solution precursors for the light-driven nanopatterning of thin films.
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Hydrolysis and Condensation of n-BuSnCl 3: Enabling Deposition of Smooth Metal Oxide Photoresist Thin Films. Inorg Chem 2020; 59:3934-3941. [PMID: 32105458 DOI: 10.1021/acs.inorgchem.9b03589] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Herein, we report hydrolysis and condensation chemistries of C4H9SnCl3 to molecular clusters and gel films. Precursor speciation plays a key role in film formation and quality toward realization of atomically smooth surfaces. Density functional theory investigations of C4H9SnCl3 and its reactions show that hydrolysis of the dimer (C4H9Sn)2(OH)2Cl4(H2O)2 has a high energetic penalty in the gas phase and when using a polarizable continuum solvation model based on density. These computations support our observed stability of the dimeric cluster in air, in various solvents, and through initial film deposition. It hydrolyzes and condenses to the [(C4H9Sn)12O14(OH)6]2+ dodecamer on-chip after a post film-deposition bake at 80 °C. Consequently, film surface smoothness is uniquely retained through on-wafer condensation.
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Monoalkyl Tin Nano-Cluster Films Reveal a Low Environmental Impact under Simulated Natural Conditions. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2019; 38:2651-2658. [PMID: 31441966 DOI: 10.1002/etc.4580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 07/10/2019] [Accepted: 08/19/2019] [Indexed: 06/10/2023]
Abstract
Recently, monoalkyl oxo-hydroxo tin clusters have emerged as a new class of metal-oxide resist to support the semiconductor industry's transition to extreme ultraviolet (EUV) lithography. Under EUV exposure, these tin-based clusters exhibit higher performance and wider process windows than conventional polymer materials. A promising new monoalkyl precursor, [(BuSn)12 O14 (OH)6 ][OH]2 (BuSn), is still in its infancy in terms of film formation. However, understanding potential environmental effects could significantly affect future development as a commercial product. We synthesized and explored the toxicity of nano-BuSn in the alga Chlamydomonas reinhardtii and the crustacean Daphnia magna at exposure concentrations ranging from 0 to 250 mg/L. Nano-BuSn had no effect on C. reinhardtii growth rate irrespective of concentration, whereas high nanoparticle concentrations (≥100 mg/L) increased D. magna immobilization and mortality significantly. To simulate an end-of-life disposal and leachate contamination, BuSn-coated film wafers were incubated in water at various pH values and temperatures for 14 and 90 d to investigate leaching rates and subsequent toxicity of the leachates. Although small quantities of tin (1.1-3.4% of deposited mass) leached from the wafers, it was insufficient to elicit a toxic response regardless of pH, incubation time, or temperature. The low toxicity of the tin-based thin films suggests that they can be an environmentally friendly addition to the material sets useful for semiconductor manufacturing. Environ Toxicol Chem 2019;38:2651-2658. © 2019 SETAC.
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Abstract
Zr/Hf aqueous-acid clusters are relevant to inorganic nanolithography, metal-organic frameworks (MOFs), catalysis, and nuclear fuel reprocessing, but only two topologies have been identified. The (Zr4) polyoxocation is the ubiquitous square aqueous Zr/Hf-oxysalt of all halides (except fluoride), and prior-debated for perchlorate. Simply adding peroxide to a Zr oxyperchlorate solution leads to a striking modification of Zr4, yielding two structures identified by single-crystal X-ray diffraction. Zr25, isolated from a reaction solution of 1:1 peroxide/Zr, is fully formulated [Zr25O10(OH)50(O2)5(H2O)40](ClO4)10·xH2O. Zr25 is a pentagonal assembly of 25 Zr-oxy/peroxo/hydroxyl polyhedra and is the largest Zr/Hf cluster topology identified to date. Yet it is completely soluble in common organic solvents. ZrTd, an oxo-centered tetrahedron fully formulated [Zr4(OH)4(μ-O2)2(μ4-O)(H2O)12](ClO4)6·xH2O, is isolated from a 10:1 peroxide/Zr reaction solution. The formation pathways of ZrTd and Zr25 in water were described by small-angle X-ray scattering (SAXS), pair distribution function (PDF), and electrospray ionization mass spectrometry (ESI-MS). Zr4 undergoes disassembly by 1 equiv of peroxide (per Zr) to yield small oligomers of Zr25 that assemble predominantly in the solid state, an unusual crystal growth mechanism. The self-buffering acidity of the Zr-center prevents Zr25 from remaining intact in water. Identical species distribution and cluster fragments are observed in the assembly of Zr25 and upon redissolution of Zr25. On the other hand, the 10:1 peroxide/Zr ratio of the ZrTd reaction solution yields larger prenucleation clusters before undergoing peroxide-promote disassembly into smaller fragments. Neither these larger cluster intermediates of ZrTd nor the smaller intermediates of Zr25 have yet been isolated and structurally characterized, and they represent an opportunity to expand this new class of group IV polycations, obtained by peroxide reactivity and ligation.
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Demonstration of Fowler-Nordheim Tunneling in Simple Solution-Processed Thin Films. ACS APPLIED MATERIALS & INTERFACES 2018; 10:36082-36087. [PMID: 30259732 DOI: 10.1021/acsami.8b08986] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The production of high-quality thin-film insulators is essential to develop advanced technologies based on electron tunneling. Current insulator deposition methods, however, suffer from a variety of limitations, including constrained substrate sizes, limited materials options, and complexity of patterning. Here, we report the deposition of large-area Al2O3 films by a solution process and its integration in metal-insulator-metal devices that exhibit I- V signatures of Fowler-Nordheim electron tunneling. A unique, high-purity precursor based on an aqueous solution of the nanocluster flat-Al13 transforms to thin Al2O3 insulators free of the electron traps and emission states that commonly inhibit tunneling in other films. Tunneling is further confirmed by the temperature independence of device current.
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Structural convergence properties of amorphous InGaZnO 4 from simulated liquid-quench methods. Dalton Trans 2017; 46:15311-15316. [PMID: 29068444 DOI: 10.1039/c7dt02181j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The study of structural properties of amorphous structures is complicated by the lack of long-range order and necessitates the use of both cutting-edge computer modeling and experimental techniques. With regards to the computer modeling, many questions on convergence arise when trying to assess the accuracy of a simulated system. What cell size maximizes the accuracy while remaining computationally efficient? More importantly, does averaging multiple smaller cells adequately describe features found in bulk amorphous materials? How small is too small? The aims of this work are: (1) to report a newly developed set of pair potentials for InGaZnO4 and (2) to explore the effects of structural parameters such as simulation cell size and numbers on the structural convergence of amorphous InGaZnO4. The total number of formula units considered over all runs is found to be the critical factor in convergence as long as the cell considered contains a minimum of circa fifteen formula units. There is qualitative agreement between these simulations and X-ray total scattering data - peak trends and locations are consistently reproduced while intensities are weaker. These new IGZO pair potentials are a valuable starting point for future structural refinement efforts.
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Group additivity-Pourbaix diagrams advocate thermodynamically stable nanoscale clusters in aqueous environments. Nat Commun 2017. [PMID: 28643782 PMCID: PMC5481758 DOI: 10.1038/ncomms15852] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The characterization of water-based corrosion, geochemical, environmental and catalytic processes rely on the accurate depiction of stable phases in a water environment. The process is aided by Pourbaix diagrams, which map the equilibrium solid and solution phases under varying conditions of pH and electrochemical potential. Recently, metastable or possibly stable nanometric aqueous clusters have been proposed as intermediate species in non-classical nucleation processes. Herein, we describe a Group Additivity approach to obtain Pourbaix diagrams with full consideration of multimeric cluster speciation from computations. Comparisons with existing titration results from experiments yield excellent agreement. Applying this Group Additivity-Pourbaix approach to Group 13 elements, we arrive at a quantitative evaluation of cluster stability, as a function of pH and concentration, and present compelling support for not only metastable but also thermodynamically stable multimeric clusters in aqueous solutions.
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14
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Alkyltin Keggin Clusters Templated by Sodium. Angew Chem Int Ed Engl 2017; 56:10140-10144. [DOI: 10.1002/anie.201701703] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Indexed: 11/11/2022]
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15
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Synthesis of an Aluminum Hydroxide Octamer through a Simple Dissolution Method. Angew Chem Int Ed Engl 2017; 56:10161-10164. [PMID: 28508441 DOI: 10.1002/anie.201702318] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Indexed: 11/11/2022]
Abstract
Multimeric oxo-hydroxo Al clusters function as models for common mineral structures and reactions. Cluster research, however, is often slowed by a lack of methods to prepare clusters in pure form and in large amounts. Herein, we report a facile synthesis of the little known cluster Al8 (OH)14 (H2 O)18 (SO4 )5 (Al8 ) through a simple dissolution method. We confirm its structure by single-crystal X-ray diffraction and show by 27 Al NMR spectroscopy, electrospray-ionization mass spectrometry, and small- and wide-angle X-ray scattering that it also exists in solution. We speculate that Al8 may form in natural water systems through the dissolution of aluminum-containing minerals in acidic sulfate solutions, such as those that could result from acid rain or mine drainage. Additionally, the dissolution method produces a discrete Al cluster on a scale suitable for studies and applications in materials science.
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Synthesis of an Aluminum Hydroxide Octamer through a Simple Dissolution Method. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201702318] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Monitoring Photochemical Reaction Pathways of Tungsten Hexacarbonyl in Solution from Femtoseconds to Minutes. J Phys Chem B 2016; 120:13161-13168. [DOI: 10.1021/acs.jpcb.6b11773] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Acid-Stable Peroxoniobophosphate Clusters To Make Patterned Films. Chemistry 2015; 21:6727-31. [DOI: 10.1002/chem.201500684] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Indexed: 11/07/2022]
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21
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Chemical and structural investigation of high-resolution patterning with HafSO(x). ACS APPLIED MATERIALS & INTERFACES 2014; 6:2917-2921. [PMID: 24502280 DOI: 10.1021/am405463u] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
High-resolution transmission electron microscopy (TEM) imaging and energy-dispersive X-ray spectroscopy (EDS) chemical mapping have been used to examine key processing steps that enable sub-20-nm lithographic patterning of the material Hf(OH)4-2x-2y(O2)x(SO4)y·qH2O (HafSOx). Results reveal that blanket films are smooth and chemically homogeneous. Upon exposure with an electron beam, the films become insoluble in aqueous tetramethylammonium hydroxide [TMAH(aq)]. The mobility of sulfate in the exposed films, however, remains high, because it is readily exchanged with hydroxide from the TMAH(aq) solution. Annealing the films after soaking in TMAH(aq) results in the formation of a dense hafnium hydroxide oxide material that can be converted to crystalline HfO2 with a high electron-beam dose. A series of 9 nm lines is written with variable spacing to investigate the cross-sectional shape of the patterned lines and the residual material found between them.
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Abstract
[Sc(2)(μ-OH)(2)(H(2)O)(6)(NO(3))(2)](NO(3))(2) has been synthesized from an aqueous scandium nitrate solution by using zinc powder as a reducing agent for nitric acid, which drives an increase in pH and forces the condensation of aqua scandium cations. This preparative route readily produces gram-scale samples with yields near 65%. A single-crystal X-ray diffraction study reveals a structure characterized by a hydroxo-bridged Sc dimer. The FTIR spectrum of the compound has been modeled via ab initio computations, allowing the identification of signature IR peaks. Some initial observations on the thermal transformation of the compound to Sc(2)O(3) are also reported.
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In-situ
characterization of aqueous-based hafnium oxide hydroxide sulfate thin films. SURF INTERFACE ANAL 2013. [DOI: 10.1002/sia.5205] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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25
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Size-Dependent Structural Distortions in One-Dimensional Nanostructures. Angew Chem Int Ed Engl 2013; 52:1982-5. [DOI: 10.1002/anie.201207825] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/13/2012] [Indexed: 11/08/2022]
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Oligomeric group 13 hydroxide compounds—a rare but varied class of molecules. Chem Soc Rev 2012; 41:1019-30. [DOI: 10.1039/c1cs15216e] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Diffractive light trapping in crystal-silicon films: experiment and electromagnetic modeling. APPLIED OPTICS 2011; 50:5728-5734. [PMID: 22015368 DOI: 10.1364/ao.50.005728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Diffractive light trapping in 1.5 μm thick crystal silicon films is studied experimentally through hemispherical reflection measurements and theoretically through rigorous coupled-wave analysis modeling. The gratings were fabricated by nanoimprinting of dielectric precursor films. The model data, which match the experimental results well without the use of any fitting parameters, are used to extract the light trapping efficiency. Diffractive light trapping is studied as a function of incidence angle, and an enhancement of light absorption is found for incidence angles up to 50° for both TE and TM polarizations.
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Abstract
A plot of electron affinity (EA) and ionization potential (IP) versus energy band gap (E(G)) for 69 binary closed-shell inorganic semiconductors and insulators reveals that E(G) is centered about the hydrogen donor/acceptor ionization energy ε(+/-). Thus, ε(+/-), or equivalently the standard hydrogen electrode (SHE) energy, functions as an absolute energy reference, determining the tendency of an atom to be either a cation or anion in a compound. This empirical trend establishes the basis for defining a new solid state energy (SSE) scale. This SSE scale makes possible simple approaches for quantitatively assessing electronegativity, chemical hardness, and ionicity, while also providing new insight into the periodic trends of solids.
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Synthesis of the Hydroxide Cluster [Al13(μ3-OH)6(μ-OH)18(H2O)24]15+ from an Aqueous Solution. Inorg Chem 2011; 50:4683-5. [DOI: 10.1021/ic200483q] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
AbstractBy considering selected examples of new structure types, guidelines are set forth for the synthesis of new solid-state inorganic borates that are likely to have desirable properties for nonlinear optical applications. The structures of two new, noncentrosymmetric orthoborate fluorides BaCaBO3F and Ba7(BO3)3F5 demonstrate a feasibility for controlling linear optical properties and for producing noncentrosymmetric borates that melt congruently. The structure of SrLi(B3O5)3 represents an additional example of a noncentrosymmetric borate resulting from chirality of the B3O7 ring. In addition to potential practical value, crystals of the type AMOB2O5 (A = K, Rb, and Cs; M = Nb and Ta) provide a unique means for examining the structural dependent interrelationships of linear and nonlinear optical properties.
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Abstract
AbstractStructural and spectroscopie characteristics of a series of Eu 2+-doped Sr and Ba borates have been studied to establish simple correlations among emission color, excitation energies, Stokes shifts, and O atom environments.
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Advancing MIM electronics: amorphous metal electrodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:74-78. [PMID: 20976677 DOI: 10.1002/adma.201002678] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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33
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Superstructure of a phosphor material Ba3MgSi2O8 determined by neutron diffraction data. J SOLID STATE CHEM 2009. [DOI: 10.1016/j.jssc.2008.11.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Abstract
Powdered samples of the perovskite BaSnO(3) exhibit strong near-infrared (NIR) luminescence at room temperature, following band-gap excitation at 380 nm (3.26 eV). The emission spectrum is characterized by a broad band centered at 905 nm (1.4 eV), tailing on the high-energy side to approximately 760 nm. The Stokes shift is 1.9 eV, and measured lifetimes in the range 7-18 ms depend on preparative conditions. These extraordinary long values indicate that the luminescence involves a defect state(s). At low temperatures, both a sharp peak and a broad band appear in the visible portion of the luminescence spectrum at approximately 595 nm. Upon cooling, the intensity of the NIR emission decreases, while the integrated intensities of the visible emission features increase to approximately 40% of the NIR intensity at 77 K. Room-temperature photoluminescence (PL) is observed across the Ba(1-x)Sr(x)SnO(3) series. As the strontium content increases, the excitation maximum and band gap shift further into the UV, while the intensity of the NIR emission peak decreases and shifts further into the infrared. This combination leads to an unexpectedly large increase in the Stokes shift. The unusual NIR PL in BaSnO(3) may originate from recombination of a photogenerated valence-band hole and an occupied donor level, probably associated with a Sn(2+) ion situated roughly 1.4 eV above the valence-band edge.
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The cubane structure of tetrakis(dimethylamine)tetraoxotetra-.mu.3-oxotetrakis(trimethylsiloxo)tetramolybdenum. Inorg Chem 2002. [DOI: 10.1021/ic00003a046] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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43
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Synthesis and structure of a new ternary chalcogenide Nb3Pd0.72Se7; interrelationships in the packing of prisms and planes. J Am Chem Soc 2002. [DOI: 10.1021/ja00312a053] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Structure and absolute stereochemistry of the epoxyquinol LL-C10037.alpha. and related metabolites from Streptomyces LL-C10037. J Org Chem 2002. [DOI: 10.1021/jo00301a039] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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50
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