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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Luminescent and structural properties of ZnO-Ag films

ZnO-Ag thin films were prepared by a two-stage method on glass and sapphire substrates. Ag doping was carried out by a method of close space sublimation at atmospheric pressure. The film thickness is varied from 0.6 to 7 {mu}m. The structural and radiative properties were explored by X-ray diffraction technique, atomic force microscopy, photoluminescence and cathodoluminescence spectroscopy. The influence of the fabricating conditions on the properties of ZnO-Ag films is studied. It is found that the Ag doping modifies the crystalline structure of the films and promotes the oriented growth of monocrystalline blocks with the size of 500-2000 nm in the [0002] direction. Improvement of the crystalline quality correlates with the change of the radiative characteristics of the films. The origin of emission centers is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Potential Pharmacologic Treatments for Cystinuria and for Calcium Stones Associated with Hyperuricosuria

Two new potential pharmacologic therapies for recurrent stone disease are described. The role of hyperuricosuria in promoting calcium stones is controversial with only some but not all epidemiologic studies demonstrating associations between increasing urinary uric acid excretion and calcium stone disease. The relationship is supported by the ability of uric acid to 'salt out' (or reduce the solubility of) calcium oxalate in vitro. A randomized, controlled trial of allopurinol in patients with hyperuricosuria and normocalciuria was also effective in preventing recurrent stones. Febuxostat, a nonpurine inhibitor of xanthine oxidase (also known as xanthine dehydrogenase or xanthine oxidoreductase) may have advantages over allopurinol and is being tested in a similar protocol, with the eventual goal of determining whether urate-lowering therapy prevents recurrent calcium stones. Treatments for cystinuria have advanced little in the past 30 years. Atomic force microscopy has been used recently to demonstrate that effective inhibition of cystine crystal growth is accomplished at low concentrations of L-cystine methyl ester and L-cystine dimethyl ester, structural analogs of cystine that provide steric inhibition of crystal growth. In vitro, L-cystine dimethyl ester had a significant inhibitory effect on crystal growth. The drug's safety and effectiveness will be tested in an Slc3a1 knockout mouse that serves as an animal model of cystinuria.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Influence of the samarium impurity on the structure and surface morphology of Se{sub 95}Te{sub 5} chalcogenide glassy semiconductor

X-ray diffraction and atomic-force microscopy are used to study the structure and surface morphology of Se{sub 95}Te{sub 5} chalcogenide glassy semiconductor films and the influence exerted on these films by doping with samarium. The parameters of the first sharp diffraction peak (FSDP), observed in X-ray diffraction patterns, are used to determine the numerical values of the local structure parameters, such as the “quasiperiod” of density fluctuations, correlation length [size of medium-range-order (MRO) regions], and nanovoid diameters. In addition, the numerical values of the roughness-amplitude parameters are determined. It is found that the disorder in the atomic structure and the irregularities on the surface of the films under study become more pronounced with increasing percentage content of the samarium impurity.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Formation of tetragonal or monoclinic ZrO{sub 2} coatings by oxygen plasma treatment of Zr{sub 74.7}Cu{sub 19.7}Nb{sub 5.6} glassy thin films

The authors report on the production of stable nanostructured tetragonal and/or monoclinic ZrO{sub 2} nanopillars achieved by means of oxygen plasma treatment of ternary Zr{sub 74.7}Cu{sub 19.7}Nb{sub 5.6} glassy films. The Zr-based metallic glass thin films were successfully deposited by magnetron sputtering and subsequently subjected to oxygen plasma for various exposure times. The compositions of the oxidized films were determined by Auger electron spectroscopy and X-Ray photoelectron spectroscopy depth profiling while the surface morphology was evaluated by means of atomic force microscopy and scanning electron microscopy. X-Ray diffraction was used for the structural analysis. Our results show that, depending on the length of time of oxygen plasma treatment, tetragonal and/or monoclinic ZrO{sub 2} films can be formed, the surface morphology of which exhibit nanopillar structures with an increased effective surface. These findings provide an easy and efficient way for growing ZrO{sub 2} coatings with a predefined structure suitable for protective and possibly for catalytic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Atomic layer deposition of zinc sulfide with Zn(TMHD){sub 2}

The atomic layer deposition (ALD) of ZnS films with Zn(TMHD){sub 2} and in situ generated H{sub 2}S as precursors was investigated, over a temperature range of 150-375 Degree-Sign C. ALD behavior was confirmed by investigation of growth behavior and saturation curves. The properties of the films were studied with atomic force microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, ultraviolet-visible-infrared spectroscopy, and extended x-ray absorption fine structure. The results demonstrate a film that can penetrate a porous matrix, with a local Zn structure of bulk ZnS, and a band gap between 3.5 and 3.6 eV. The ZnS film was used as a buffer layer in nanostructured PbS quantum dot solar cell devices.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Ag Addition on the Surface Topography and the Vibrational Dynamics of MgB{sub 2}

We fabricated MgB{sub 2} samples with Ag additions using in situ solid-state reaction via a single-step sintering to study the effect of Ag on the structural, vibration, and superconducting properties of MgB{sub 2} samples. Ag addition to MgB{sub 2} resulted in a significant improvement in J{sub c} although no appreciable effect was observed in the lattice parameters and the superconducting transition temperature T{sub c}. Dramatic increase in the grain size was observed with Ag addition and topographic measurements with atomic force microscopy revealed the formation of Ag–Mg nanoparticles 5–20 nm in size at 2 and 4 wt% Ag additions. The fact that these samples showed high J{sub c} values suggests that the nanoparticles formed as a result of Ag addition are responsible for enhanced flux pinning. Raman spectroscopy measurements showed that Ag additions also increased disorder in the system and thereby affected the line width of the Raman active E{sub 2g} mode.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Grafted polythiophene pendent polymer brushes and their electronanopatterning

Here electrochemical nanolithography using grafted polymer brushes with terthiophene (3T) pendent was investigated. The film was fabricated by surface electropolymerization of a reversible addition-fragmentation chain-transfer agent macroinitiator containing a 3T pendant molecule and the subsequent polymer brush growth from a 3T functionalized methacrylate monomer (3T-Methacrylate). Electrochemical nanolithography and patterning were done using conducting atomic force microscopy (C-AFM) enabling precise nanopattern fabrication. In contrast to direct nanowriting, dip pen nanolithography, and nanolithographic additive manufacturing, the electrochemical nanolithography can be readily facilitated by applying a bias voltage between a conductive AFM tip and the grafted polymer brush film at ambient conditions and without ink transfer. The height and electrical resistance of the nanopatterns were dependent on the writing parameters (i.e. applied bias voltage and scan rate).

36 MATERIALS SCIENCE↗
DOE OSTI2010

A comprehensive study of the influence of the stoichiometry on the physical properties of TiO{sub x} films prepared by ion beam deposition

A comprehensive study of nonstoichiometry titanium oxide thin films (TiO{sub x}, 0.3{<=}x{<=}2) prepared by ion beam deposition technique is reported. The physical properties of the material are studied by ultraviolet and x-ray photoelectron, Raman, and Fourier transform infrared spectroscopies, and atomic force microscopy. An abrupt transition from metallic characteristics to a wide gap semiconductor is observed in a very narrow range of oxygen variation. Concomitantly with this change the crystal structure and morphology suffer remarkable physical properties modifications. This transformation is ascribed to surface-volume energy minimization due to the influence of oxygen determining the size of the TiO{sub 2} particles during coalescence.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Quasi-two-dimensional conducting layer on TiO{sub 2} (110) introduced by sputtering as a template for resistive switching

The insulator-to-metal transformation in the surface layer of TiO{sub 2} (110) induced by the Ar{sup +} ion sputtering process is analyzed on the nanoscale. Local conductivity atomic force microscopy and photoelectron spectroscopy allow the changes in the valence of the Ti ions in the surface layer to be linked to the formation of its grain-like structure. The investigation of the cleavage plane of the crystal allowed us to estimate the thickness of the quasi-two-dimensional conducting layer generated by ion bombardment as 30 nm. The conducting layer is a template where the resistive switching of each single grain can be carried out.

36 MATERIALS SCIENCE↗
DOE OSTI2014

A vacuum microgripping tool with integrated vibration releasing capability

Pick-and-place of micro-objects is a basic task in various micromanipulation demands. Reliable releasing of micro-objects is usually disturbed due to strong scale effects. This paper focuses on a vacuum micro-gripper with vibration releasing functionality, which was designed and assembled for reliable micromanipulation tasks. Accordingly, a vibration releasing strategy of implementing a piezoelectric actuator on the vacuum microgripping tool is presented to address the releasing problem. The releasing mechanism was illustrated using a dynamic micro contact model. This model was developed via theoretical analysis, simulations and pull-off force measurement using atomic force microscopy. Micromanipulation experiments were conducted to verify the performance of the vacuum micro-gripper. The results show that, with the assistance of the vibration releasing, the vacuum microgripping tool can achieve reliable release of micro-objects. A releasing location accuracy of 4.5±0.5 μm and a successful releasing rate of around 100% (which is based on 110 trials) were achieved for manipulating polystyrene microspheres with radius of 35–100 μm.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Synthesis, characterization of WS{sub 2} nanostructures by vapor phase deposition

Ultrathin two-dimensional WS{sub 2} nanostructures with various morphologies have been prepared on SiO{sub 2}/Si (300 nm) and sapphire substrates by vapor phase deposition method. Simultaneously, tungsten nanostructures have also been obtained during the growth process. The nanostructures and morphologies of as-prepared products were systematically characterized by employing atomic force microscopy, Raman spectroscopy as well as scanning electron spectroscopy. The electrostatic properties of WS{sub 2} nanostructures were investigated exhibiting uniform surface potential and charge distributions. We have also detected the photoluminescence properties of WS{sub 2} nanostructures, which are dependent on the thickness and nanostructures of synthesized WS{sub 2}. These results suggest that the optoelectronic properties of WS{sub 2} nanostructures can be effectively tuned by quantum confinement effect and nanostructures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Investigations on rectifying behavior of Y{sub 0.95}Ca{sub 0.05}MnO{sub 3}/Si junction

In this communication, we report the rectifying properties observed across the junction, consists of Ca{sup +2} doped hexagonal YMnO{sub 3} manganite film, grown on n-type (100) Si single crystalline substrate. The junction was grown using cost effective chemical solution deposition (CSD) technique by employing spin coating method. Surface morphology of Y{sub 0.9}5Ca{sub 0.05}MnO{sub 3}/Si (YCMO/Si) film was carried out by atomic force microscopy and magnetic response of film was studied by magnetic force microscopy. Current – voltage characteristics of the junction was carried out by using Keithley source meter in current perpendicular to plane (CPP) mode at different temperatures. Rectification in I – V behavior has been observed for the junction at all the temperatures studied. With increase in temperature, rectification ratio, in the range of 10{sup 4}, increases across the junction. Results have been discussed in the context of thermal effects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2010

Structural organization of films based on polyaniline/polysulfonic acid complexes depending on the synthesis method

The optical properties and morphology of complexes based on polyaniline (PANI) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS), depending on their synthesis conditions, have been characterized by UV-visible spectroscopy and atomic force microscopy. The dependence of the electron absorption spectra of PANI/PAMPS complexes and the surface topography of their films on the initiation way of PANI formation (chemical and enzymatic) and the use of promoters of aniline polymerization has been investigated. The aniline polymerization kinetics with and without polymerization promoters has been studied. All PANI/PAMPS complexes are found to have a nanocomposite time-stable structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Processing and structural properties of random oriented lead lanthanum zirconate titanate thin films

Highlights: • Pyrochlore phase crystallizes near the bottom film-electrode interface. • PLZT films show a non-uniform microstrain and crystallite size in depth profile. • Complex grainy structure leads to different elastic modulus at the nanoscale. - Abstract: Polycrystalline lead lanthanum zirconate titanate (PLZT) thin films have been prepared by a polymeric chemical route to understand the mechanisms of phase transformations and map the microstructure and elastic properties at the nanoscale in these films. X-ray diffraction, atomic force microscopy (AFM) and ultrasonic force microscopy (UFM) have been used as investigative tools. On one side, PLZT films with mixed-phase show that the pyrochlore phase crystallizes predominantly in the bottom film-electrode interface while a pure perovskite phase crystallizes in top film surface. On the contrary, pyrochlore-free PLZT films show a non-uniform microstrain and crystallite size along the film thickness with a heterogeneous complex grainy structure leading to different elastic properties at nanoscale.

36 MATERIALS SCIENCE↗
DOE OSTI2010

Femtosecond Pulse Tailoring For Nanoscale Laser Processing Of Wide-Bandgap Materials: Temporal Asymmetric Pulses Versus Frequency Sweeps

Control of two basic ionization processes in dielectrics i.e. photo ionization and electron-electron impact ionization on intrinsic time and intensity scales is investigated experimentally. In our experiment, we use a modified microscope set up to irradiate the surface of a fused silica sample with a single shaped pulse resulting in nanoscale ablation structures. The topology of the laser generated structures is measured by Atomic Force Microscopy (AFM). Structure parameters are investigated as a function of the pulse energy and the modulation parameters. We find different thresholds for surface material modification with respect to an asymmetric temporal pulse and its time reversed counterpart both showing a constant instantaneous frequency. However, we do not observe pronounced differences between up- and down-chirped radiation (i.e. symmetric temporal pulse envelope but asymmetric instantaneous frequency) in the measured structure diameters and thresholds.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Volmer-Weber growth of AlSb on Si(111)

AlSb is grown by molecular beam epitaxy. The evolution and the relaxation of the deposited AlSb layer is investigated by synchrotron-based in situ grazing incidence x-ray diffraction (GID), and the analysis of the real space distribution is performed by atomic force microscopy. AlSb forms islands with (111)A polarity and {l_brace}110{r_brace} surface orientations with different side facets following the Volmer-Weber growth mode. GID investigations reveal facet rods originating from AlSb{l_brace}110{r_brace} islands. It is shown that a concentration of only 0.7% AlSb{l_brace}110{r_brace} oriented domains influences the diffraction pattern in such a way that additional crystal truncation rods parallel to the surface appear.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Impact of the GaN nanowire polarity on energy harvesting

We investigate the piezoelectric generation properties of GaN nanowires (NWs) by atomic force microscopy equipped with a Resiscope module for electrical measurements. By correlating the topography profile of the NWs with the recorded voltage peaks generated by these nanostructures in response to their deformation, we demonstrate the influence of their polarity on the rectifying behavior of the Schottky diode formed between the NWs and the electrode of measurement. These results establish that the piezo-generation mechanism crucially depends on the structural characteristics of the NWs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Effect of L1{sub 2} ordering in antiferromagnetic Ir-Mn epitaxial layer on exchange bias of FePd films

Two series of samples of single-layer IrMn and IrMn/FePd bilayer films, deposited on a single-crystal MgO substrate at different IrMn deposition temperatures (T{sub s} = 300–700 °C), were investigated using magnetron sputtering. L1{sub 2} ordering was revealed for the 30 nm-thick IrMn epitaxial (001) films with T{sub s} ≥ 400 °C, determined by synchrotron radiation x-ray diffractometry (XRD). XRD results also provide evidence of the epitaxial growth of the IrMn films on MgO substrate. Increasing T{sub s} from 400 to 700 °C monotonically increases the ordering parameter of L1{sub 2} phases from 0.17 to 0.81. An in-plane exchange bias field (H{sub eb}) of 22 Oe is obtained in a 10 nm-thick FePd film that is deposited on the disordered IrMn films. As the L1{sub 2} ordering of the IrMn layers increases, the H{sub eb} gradually decreases to 0 Oe, meaning that the exchange bias behavior vanishes. The increased surface roughness, revealed by atomic force microscopy, of the epitaxial IrMn layers with increasing T{sub s} cannot be the main cause of the decrease in H{sub eb} due to the compensated surface spins regardless of the disordered and ordered (001) IrMn layers. The change of antiferromagnetic structure from the A1 to the L1{sub 2} phase was correlated with the evolution of H{sub eb}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗