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2009 International Conference on Neutron Scattering (ICNS 2009)

Description: The ICNS provides a focal point for the worldwide neutron user community to strengthen ties within this diverse group, while at the same time promoting neutron research among colleagues in related disciplines identified as “would-be” neutron users. The International Conference on Neutron Scattering thus serves a dual role as an international user meeting and a scientific meeting. As a venue for scientific exchange, the ICNS showcases recent results and provides forums for scientific discussion of neutron research in diverse fields such as hard and soft condensed matter, liquids, biology, magnetism, engineering materials, chemical spectroscopy, crystal structure, and elementary excitations, fundamental physics and development of neutron instrumentation through a combination of invited talks, contributed talks and poster sessions. Each of the major national neutron facilities (NIST, LANSCE, ANL, HFIR and SNS), along with their international counterparts, has an opportunity to exchange information with each other and to update users, and potential users, of their facility. This is also an appropriate forum for users to raise issues that relate to the facilities.
Date: August 5, 2010
Creator: Rao, Gopal & Gillespie, Donna
Partner: UNT Libraries Government Documents Department

Scientific/Techical Report

Description: The ACNS provides a focal point for the North American neutron user community, strengthening ties within this diverse group, and promoting neutron research in related disciplines. The conference thus serves a dual role as both a national user meeting and a scientific meeting. As a venue for scientific exchange, the ACNS showcases recent results and provides a forum for scientific discussion of neutron-enabled research in fields as diverse as hard and soft condensed matter, liquids, biology, magnetism, engineering materials, chemical spectroscopy, crystal structure, elementary excitations, fundamental physics, and development of neutron instrumentation. This is achieved through a combination of invited oral presentations, contributed oral presentations, and poster sessions. Adequate opportunity for spontaneous discussion and collaboration is also built into the ACNS program in order to foster free exchange of new scientific ideas and the potential for use of powerful neutron scattering methods beyond the current realms of application. The sixth American Conference on Neutron Scattering (ACNS 2012) provided essential information on the breadth and depth of current neutron-related research worldwide. A strong program of plenary, invited and contributed talks showcased recent scientific results in neutron science in a wide range of fields, including soft and hard condensed matter, biology, chemistry, energy and engineering applications, and neutron physics.
Date: November 7, 2012
Creator: Dr. Chris Leighton, Neutron Scattering Society of American & Mr. J. Ardie (Butch) Dillen, MRS Director of Finance and Administration
Partner: UNT Libraries Government Documents Department

Scientific/Technical Report

Description: This symposium aimed to bring together researchers working on quantifying nanoscale carrier transport processes in excitonic solar cells. Excitonic solar cells, including all-organic, hybrid organic-inorganic and dye-sensitized solar cells (DSSCs), offer strong potential for inexpensive and large-area solar energy conversion. Unlike traditional inorganic semiconductor solar cells, where all the charge generation and collection processes are well understood, these excitonic solar cells contain extremely disordered structures with complex interfaces which results in large variations in nanoscale electronic properties and has a strong influence on carrier generation, transport, dissociation and collection. Detailed understanding of these processes is important for fabrication of highly efficient solar cells. Efforts to improve efficiency are underway at a large number of research groups throughout the world focused on inorganic and organic semiconductors, photonics, photophysics, charge transport, nanoscience, ultrafast spectroscopy, photonics, semiconductor processing, device physics, device structures, interface structure etc. Rapid progress in this multidisciplinary area requires strong synergetic efforts among researchers from diverse backgrounds. Such efforts can lead to novel methods for development of new materials with improved photon harvesting and interfacial treatments for improved carrier transport, process optimization to yield ordered nanoscale morphologies with well-defined electronic structures.
Date: November 21, 2012
Creator: Bommissetty, Venkat
Partner: UNT Libraries Government Documents Department

MRS Bulletin April 2008 Volume 33 No. 4 Harnessing Materials for Energy

Description: The MRS Bulletin special expanded issue, “Harnessing Materials for Energy,” focuses on the most important materials research challenges that need to be addressed to move toward secure, affordable, and environmentally sustainable energy to meet the world’s accelerating energy needs. The issue follows the full energy chain including production, storage, distribution, use, and efficiency. The articles are designed to present an objective and global view of the energy challenges within each energy sector and the promising transformational materials research directions for meeting these challenges as far into the future as is scientifically feasible to consider (targeting 10-, 25-, and 50-year outlooks). This issue was launched at the 2008 MRS Spring Meeting with an Energy Forum featuring presentations by leading experts in the field.
Date: April 1, 2008
Creator: Arunachalam, V. S. & Fleischer, Elizabeth L.
Partner: UNT Libraries Government Documents Department

S09 Symposium KK, Structure-Property Relationships in Biomineralized and Biomimetic Composites

Description: The technical presentations and discussions at this symposium disseminated and assessed current research and defined future directions in biomaterials research, with a focus on structure-function relationships in biological and biomimetic composites. The invited and contributed talks covered a diverse range of topics from fundamental biology, physics, chemistry, and materials science to potential applications in developing areas such as light-weight composites, multifunctional and smart materials, biomedical engineering, and nanoscaled sensors. The invited speakers were chosen to create a stimulating program with a mixture of established and junior faculty, industrial and academic researchers, and American and international experts in the field. This symposium served as an excellent introduction to the area for younger scientists (graduate students and post-doctoral researchers). Direct interactions between participants also helped to promote potential future collaborations involving multiple disciplines and institutions.
Date: June 7, 2010
Creator: Kisailus, David; Estroff, Lara; Gupta, Himadri S.; Landis, William J. & Zavattieri, Pablo D.
Partner: UNT Libraries Government Documents Department

Quantitative Characterization of Nanostructured Materials

Description: The two-and-a-half day symposium on the "Quantitative Characterization of Nanostructured Materials" will be the first comprehensive meeting on this topic held under the auspices of a major U.S. professional society. Spring MRS Meetings provide a natural venue for this symposium as they attract a broad audience of researchers that represents a cross-section of the state-of-the-art regarding synthesis, structure-property relations, and applications of nanostructured materials. Close interactions among the experts in local structure measurements and materials researchers will help both to identify measurement needs pertinent to real-world materials problems and to familiarize the materials research community with the state-of-the-art local structure measurement techniques. We have chosen invited speakers that reflect the multidisciplinary and international nature of this topic and the need to continually nurture productive interfaces among university, government and industrial laboratories. The intent of the symposium is to provide an interdisciplinary forum for discussion and exchange of ideas on the recent progress in quantitative characterization of structural order in nanomaterials using different experimental techniques and theory. The symposium is expected to facilitate discussions on optimal approaches for determining atomic structure at the nanoscale using combined inputs from multiple measurement techniques.
Date: August 5, 2010
Creator: Dr. Frank (Bud) Bridges, University of California-Santa Cruz
Partner: UNT Libraries Government Documents Department

Technical Report

Description: The 2011 World Materials Summit, held on 10/9-12/2011 in Washington DC, provided a forum for top decision makers and energy experts from aropund the world to focus on the materials research needs for the growing energy economy. Organized jointly by the Materials Research Society (MRS), the European MRS (E-MRS), and the Chinese MRS (C-MRS), the goal of the Summit was to explore how the different regions of the world can work together on the critical issue of clean energy, including its relation to environmental sustainability and water. The participants considered the area of materials research as well as advocacy, economics, outreach, and education. Realizing that the concerns are long-term and that young players will ultimately be the ones who are going to need to solve the energy challenges, the chairs of the Summit inaugurated a Student Congress, a program for graduate students and postdoctoral scholars in fields directly related to energy and environmental science, engineering, and/or policy. The top 45 candidates coming from 18 countries were selected on a competititve basis to participate in the Student Congress. The four-day effort culminated in a 2011 Worlds Materials Summit Declaration delineating materials directions related to global access to clean energy and water in a sustainable way.
Date: February 1, 2012
Partner: UNT Libraries Government Documents Department

Characterization of chemical bonding in low-k dielectric materialsfor interconnect isolation: a xas and eels study

Description: The use of low dielectric constant materials in the on-chipinterconnect process reduces interconnect delay, power dissipation andcrosstalk noise. To achieve the requirements of the ITRS for 2007-2009minimal sidewall damage from etch, ash or cleans is required. In chemicalvapor deposited (CVD) organo-silicate glass (OSG) which are used asintermetal dielectric (IMD) materials the substitution of oxygen in SiO2by methyl groups (-CH3) reduces the permittivity significantly (from 4.0in SiO2 to 2.6-3.3 in the OSG), since the electronic polarizability islower for Si-C bonds than for Si-O bonds. However, plasma processing forresist stripping, trench etching and post-etch cleaning removes C and Hcontaining molecular groups from the near-surface layer of OSG.Therefore, compositional analysis and chemical bonding characterizationof structured IMD films with nanometer resolution is necessary forprocess optimization. OSG thin films as-deposited and after plasmatreatment are studied using X-ray absorption spectroscopy (XAS) andelectron energy loss spectroscopy (EELS). In both techniques, the finestructure near the C1s absorption or energy loss edge, respectively,allows to identify C-H, C-C, and C-O bonds. This gives the opportunity todifferentiate between individual low-k materials and their modifications.The O1s signal is less selective to individual bonds. XAS spectra havebeen recorded for non-patterned films and EELS spectra for patternedstructures. The chemical bonding is compared for as-deposited andplasma-treated low-k materials. The Fluorescence Yield (FY) and the TotalElectron Yield (TEY) recorded while XAS measurement are compared.Examination of the C 1s near-edge structures reveal a modified bonding ofthe remaining C atoms in the plasma-treated sample regions.
Date: April 10, 2006
Creator: Hoffmann, P.; Schmeisser, D.; Engelmann, H.-J.; Zschech, E.; Stegmann, H.; Himpsel, F. et al.
Partner: UNT Libraries Government Documents Department

Soft X-ray synchrotron radiation investigations of actinidematerials systems utilizing X-ray emission spectroscopy and resonantinelastic X-ray scattering

Description: Synchrotron radiation (SR) methods have been utilized with increasing frequency over the past several years to study topics in actinide science, ranging from those of a fundamental nature to those that address a specifically-targeted technical need. In particular, the emergence of microspectroscopic and fluorescence-based techniques have permitted investigations of actinide materials at sources of soft x-ray SR. Spectroscopic techniques with fluorescence-based detection are useful for actinide investigations since they are sensitive to small amounts of material and the information sampling depth may be varied. These characteristics also serve to simplify both sample preparation and safety considerations. Examples of investigations using these fluorescence techniques will be described along with their results, as well as the prospects for future investigations utilizing these methodologies.
Date: January 3, 2004
Creator: Shuh, D.K.; Butorin, S.M.; Guo, J.-H. & Nordgren, J.
Partner: UNT Libraries Government Documents Department

AnGa{sub 2}O{sub 4} Thin-Film Phosphors Grown by Pulsed Laser Ablation

Description: The growth and properties of undoped and Mn-doped ZnGa{sub 2}O{sub 4} thin-film phosphors on (100) MgO and glass substrates using pulsed laser ablation were investigated. Blue-white and green emission were observed for as-deposited undoped and Mn-doped films, respectively. Luminescent properties as well as crystallinity were considerably affected by processing conditions and film stoichiometry. Films with enhanced luminescent characteristics were obtained on single crystal substrates without post-annealing.
Date: April 5, 1999
Creator: Lee, Y. E.; Rouleau, C. M.; Park, C. & Norton, D. P.
Partner: UNT Libraries Government Documents Department

Germanium Nanocrystals Embedded in Sapphire

Description: {sup 74}Ge nanocrystals are formed in a sapphire matrix by ion implantation followed by damage. Embedded nanocrystals experience large compressive stress relative to bulk, as embedded in sapphire melt very close to the bulk melting point (Tm = 936 C) whereas experience considerably lower stresses. Also, in situ TEM reveals that nanocrystals ion-beam-synthesized nanocrystals embedded in silica are observed to be spherical and measured by Raman spectroscopy of the zone center optical phonon. In contrast, reveals that the nanocrystals are faceted and have a bi-modal size distribution. Notably, the matrix remains crystalline despite the large implantation dose and corresponding thermal annealing. Transmission electron microscopy (TEM) of as-grown samples those embedded in silica exhibit a significant melting point hysteresis around T{sub m}.
Date: April 15, 2005
Creator: Xu, Q.; Sharp, I. D.; Liao, C. Y.; Yi, D. O.; Ager, J. W., III; Beeman, J. W. et al.
Partner: UNT Libraries Government Documents Department

Behavior of Uranium (VI) during HEDPA Leaching for Aluminum Dissolution in Tank Waste Sludges

Description: Batch adsorption/dissolution experiments were conducted toexamine the interactions between 233U(VI) and a synthetic aluminumoxyhydroxide (boehmite, g-AlOOH) in 1.0M NaCl suspensions containing1-hydroxyethane-1,1-diphosphonic acid (HEDPA). In the pH range 4 to 9,complexation of Al(III) by HEDPA significantly enhanced dissolution ofboehmite. This phenomenon was especially pronounced in the neutral pHregion where the solubility of aluminum, in the absence of complexants,is limited by the formation of sparsely soluble aluminum hydroxides. Athigh pH levels, dissolution of synthetic boehmite was inhibited by HEDPA,likely due to sorption of Al(III)/HEDPA complexes. Addition of HEDPA toequilibrated U(VI)-synthetic boehmite suspensions yielded an increase inthe aqueous phase uranium concentration. The concentration of uraniumcontinually increased over 59 days. Partitioning of uranium between thesolid and aqueous phase was found to correlate well with HEDPApartitioning.
Date: January 4, 2006
Creator: Powell, Brian A.; Rao, Linfeng; Nash, Kenneth L. & Martin, Leigh
Partner: UNT Libraries Government Documents Department

A Chemical Approach to 3-D Lithographic Patterning of Si and GeNanocrystals

Description: Ion implantation into silica followed by thermal annealingis an established growth method for Si and Ge nanocrystals. Wedemonstrate that growth of Group IV semiconductor nanocrystals can besuppressed by co-implantation of oxygen prior to annealing. For Sinanocrystals, at low Si/O dose ratios, oxygen co-implantation leads to areduction of the average nanocrystal size and a blue-shift of thephotoluminescence emission energy. For both Si and Ge nanocrystals, atlarger Si/O or Ge/O dose ratios, the implanted specie is oxidized andnanocrystals do not form. This chemical deactivation was utilized toachieve patterned growth of Si and Ge nanocrystals. Si was implanted intoa thin SiO2 film on a Si substrate followed by oxygen implantationthrough an electron beam lithographically defined stencil mask. Thermalannealing of the co-implanted structure yields two-dimensionallypatterned growth of Si nanocrystals under the masked regions. We applieda previously developed process to obtain exposed nanocrystals byselective HF etching of the silica matrix to these patterned structures.Atomic force microscopy (AFM) of etched structures revealed that exposednanocrystals are not laterally displaced from their original positionsduring the etching process. Therefore, this process provides a means ofachieving patterned structures of exposed nanocrystals. The possibilitiesfor scaling this chemical-based lithography process to smaller featuresand for extending it to 3-D patterning is discussed.
Date: December 12, 2005
Creator: Sharp, I. D.; Xu, Q.; Yi, D. O.; Liao, C. Y.; Ager, J. W., III; Beeman, J. W. et al.
Partner: UNT Libraries Government Documents Department

Electronic and Optical Properties of Energetic Particle-IrradiatedIn-rich InGaN

Description: We have carried out a systematic study of the effects of irradiation on the electronic and optical properties of InGaN alloys over the entire composition range. High energy electrons, protons, and {sup 4}He{sup +} were used to produce displacement damage doses (D{sub d}) spanning over five orders of magnitude. The free electron concentrations in InN and In-rich InGaN increase with D{sub d} and finally saturate after a sufficiently high D{sub d}. The saturation of carrier density is attributed to the formation of native donors and the Fermi level pinning at the Fermi Stabilization Energy (E{sub FS}), as predicted by the amphoteric native defect model. Electrochemical capacitance-voltage (ECV) measurements reveal a surface electron accumulation whose concentration is determined by pinning at E{sub FS}.
Date: April 13, 2005
Creator: Li, S. X.; Yu, K. M.; Jones, R. E.; Wu, J.; Walukiewicz, W.; AgerIII, J. W. et al.
Partner: UNT Libraries Government Documents Department

In/Si(111): Self-assembled one and two-dimensional electrongases

Description: We present angle-resolved photoemission measurements forultrathin In films on Si(111). Depending on the coverage, this systemself-organizes into a metallic monolayer with either 4x1 or sqrt7 x sqrt3symmetry relative to the substrate. Electronically, they behave likeideal one- and two-dimensional electron gases (1DEG and 2DEG),respectively. The 4x1 system has atomic chains of In whose energy bandsdisperse only parallel to the chains, while for the sqrt7 x sqrt3 system,the dominant reciprocal space features (in both diffraction andbandstructure) resemble a pseudo-square lattice with only weakersecondary features relating to the sqrt7 x sqrt3 periodicity. In bothmaterials the electrons show coupling to the structure. The 1DEG couplesstrongly to phonons of momentum 2kF, leading to an 8x"2" Peierls-likeinsulating ground state. The 2DEG appears to be partially stabilized byelectron gap formation at the sqrt 7 x sqrt3 zone boundary.
Date: January 22, 2001
Creator: Rotenberg, Eli; Yeom, H. W.; Takeda, S.; Matsuda, I.; Horikoshi, K.; Schaefer, J. et al.
Partner: UNT Libraries Government Documents Department

Z-Contrast STEM Imaging and EELS of CdSe Nanocrystals: Towards the Analysis of Individual Nanocrystal Surfaces

Description: We have applied Atomic Number Contract Scanning Transmission Electron Microscopy (Z-Contrast STEM) and STEM/EELS (Electron Energy Loss Spectroscopy) towards the study of colloidal CdSe semiconductor nanocrystals embedded in MEH-PPV polymer films. Unlike the case of conventional phase-contrast High Resolution TEM, Z-Contrast images are direct projections of the atomic structure. Hence they can be interpreted without the need for sophisticated image simulation and the image intensity is a direct measure of the thickness of a nanocrystal. Our thickness measurements are in agreement with the predicted faceted shape of these nanocrystals. Our unique 1.3A resolution STEM has successfully resolve3d the sublattice structure of these CdSe nanocrystals. In [010] projection (the polar axis in the image plane) we can distinguish Se atom columns from Cd columns. Consequently we can study the effects of lattice polarity on the nanocrystal morphology. Furthermore, since the STEM technique does not rely on diffraction, it is superbly suited to the study of non-periodic detail, such as the surface structure of the nanocrystals. EELS measurements on individual nanocrystals indicate a significant amount (equivalet to 0.5-1 surface monolayers) of oxygen on the nanocrystals, despite processing in an inert atmosphere. Spatially resolved measurements at 7A resolution suggest a surface oxide layer. However, the uncertainty in the measurement precludes definitive assignment at this time. The source of the oxygen is under investigation as well.
Date: April 5, 1999
Creator: Erwin, M.; Kadavanich, A. V.; Kippeny, T.; Pennycook, S. J. & Rosenthal, S. J.
Partner: UNT Libraries Government Documents Department

Strain and Texture in Al-Interconnect Wires Measured by X-Ray Microbeam Diffraction

Description: The local strain and texture in Al interconnect wires have been investigated using white and monochromatic x-ray microbeams on the MHATTCAT undulator beam line at the Advanced Photon Source. Intergrain and intragrain orientations were obtained with ~0.01 degree sensitivity using white beam measurements on wide Al pads (~100 Mu-m) and thin (2 Mu-m) Al wires. Orientation changes of up to 1 degree were found within individual grains of the (111) textured Al interconnects. Deviatoric strain measurements indicate small intragranular strain variations, but intergranular strain variations were found to be quite large.
Date: April 5, 1999
Creator: Budai, J. D.; Chung, J.-S.; Ice, G. E.; Larson, B. C.; Lowe, W. P.; Tamura, N. et al.
Partner: UNT Libraries Government Documents Department

Complexation of actinides with derivatives of oxydiaceticacid

Description: Complexation of Np(V), U(VI) and Nd(III) with dimethyl-3-oxa-glutaramic acid (DMOGA) and tetramethyl-3-oxa-glutaramide (TMOGA) was studied in comparison with the complexation with oxydiacetic acid (ODA). Stability constants and enthalpy of complexation were determined by potentiometry, spectrophotometry and calorimetry. Thermodynamic parameters, in conjunction with structural information of solid compounds, indicate that DMOGA and TMOGA form tridentate complexes with the ether-oxygen participating in bonding with actinide/lanthanide ions. The trends in the stability constants, enthalpy and entropy of complexation are discussed in terms of the difference in the hydration of the amide groups and carboxylate groups and the difference in the charge density of the metal ions.
Date: January 4, 2006
Creator: Rao, Linfeng & Tian, Guoxin
Partner: UNT Libraries Government Documents Department