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Results for “Optical Absorption”

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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Heterobinuclear Light Absorber Coupled to Molecular Wire for Charge Transport across Ultrathin Silica Membrane for Artificial Photosynthesis

Coupling of robust, all-inorganic heterobinuclear light absorbers to metal oxide catalysts for water oxidation across an ultrathin product-separating silica membrane requires charge transfer through organic molecular wires embedded in the silica. A synthetic approach for assembling the bimetallic units on the silica surface is introduced that is compatible with the presence of encapsulated organic molecules. Accurate selection and fine tuning of the concentration of embedded conducting wires are enabled by a two-step method consisting of surface attachment of a tripodal anchor, trimethoxysilyl aniline, followed by attachment of p-oligo(phenylene vinylene) through amide linkage. Each step of the assembly process was monitored and characterized by a combination of Fourier transform infrared, Fourier transform-Raman, and UV-vis spectroscopy techniques. Hole transfer was observed from transient Co III , formed by Ti IV OCo II → Ti III OCo III charge transfer excitation of the chromophore, to p-oligo(phenylene vinylene) molecule within the 8 ns width of the photolysis laser pulse by transient optical absorption spectroscopy of the wire radical cation. The rectifying property of the light absorber-wire assembly enabled by appropriate selection of redox potentials of metals and embedded wire obviates the need for a molecularly defined linkage between the components. Combined with the previously observed ultrafast hole injection from the embedded wires to Co oxide catalyst, the result implies visible-light-induced hole transfer from visible-light-excited binuclear light absorber to water oxidation catalyst across the silica separation membrane in a few nanoseconds or faster. Finally, demonstration and understanding of this interfacial charge-transfer step is critical for developing nanoscale core-shell architectures for complete photosynthetic cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Excitons in ultrathin organic-inorganic perovskite crystals

In this work, we demonstrate the formation of large sheets of layered organic-inorganic perovskite (OIPC) crystals, as thin as a single unit cell, prepared by mechanical exfoliation. The resulting two-dimensional OIPC nanosheets of 2.4 nm thickness are direct semiconductors with an optical band gap of 2.4 eV. They exhibit unusually strong light-matter interaction with an optical absorption as high as 25% at the main excitonic resonance, as well as bright photoluminescence. We extract an exciton binding energy of 490 meV from measurement of the series of excited exciton states. The properties of the excitons are shown to be strongly influenced by the changes in the dielectric surroundings. The environmental sensitivity of these ultrathin OIPC sheets is further reflected in the strong suppression of a thermally driven phase transition present in the bulk crystals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Review—hexagonal boron nitride epilayers: Growth, optical properties and device applications

This paper provides a brief overview on recent advances made in authors’ laboratory in epitaxial growth and optical studies of hexagonal boron nitride (h-BN) epilayers and heterostructures. Photoluminescence spectroscopy has been employed to probe the optical properties of h-BN. It was observed that the near band edge emission of h-BN is unusually high and is more than two orders of magnitude higher than that of high quality AlN epilayers. It was shown that the unique quasi-2D nature induced by the layered structure of h-BN results in high optical absorption and emission. The impurity related and near band-edge transitions in h-BN epilayers were probed for materials synthesized under varying ammonia flow rates. Our results have identified that the most dominant impurities and deep level defects in h-BN epilayers are related to nitrogen vacancies. By growing h-BN under high ammonia flow rates, nitrogen vacancy related defects can be eliminated and epilayers exhibiting pure free exciton emission have been obtained. Deep UV and thermal neutron detectors based on h-BN epilayers were shown to possess unique features. Lastly, it is our belief that h-BN will lead to many potential applications from deep UV emitters and detectors, radiation detectors, to novel 2D photonic and electronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2015

WE-AB-303-04: A Tissue Model of Cherenkov Emission From the Skin Surface During Megavoltage X-Ray Radiotherapy

Purpose: To develop a tissue model of Cherenkov radiation emitted from the skin surface during external beam radiotherapy. Imaging Cherenkov radiation emitted from human skin allows visualization of the beam position and potentially surface dose estimates, and our goal is to characterize the optical properties of these emissions. Methods: We developed a Monte Carlo model of Cherenkov radiation generated in a semi-infinite tissue slab by megavoltage x-ray beams with optical transmission properties determined by a two-layered skin model. We separate the skin into a dermal and an epidermal layer in our model, where distinct molecular absorbers modify the Cherenkov intensity spectrum in each layer while we approximate the scattering properties with Mie and Rayleigh scattering from the highly structured molecular organization found in human skin. Results: We report on the estimated distributions of the Cherenkov wavelength spectrum, emission angles, and surface distribution for the modeled irradiated skin surface. The expected intensity distribution of Cherenkov radiation emitted from skin shows a distinct intensity peak around 475 nm, the blue region of the visible spectrum, between a pair of optical absorption bands in hemoglobin and a broad plateau beginning near 600 nm and extending to at least 700 nm where melanin and hemoglobin absorption are both low. We also find that the Cherenkov intensity decreases with increasing angle from the surface normal, the majority being emitted within 20 degrees of the surface normal. Conclusion: Our estimate of the spectral distribution of Cherenkov radiation emitted from skin indicates an advantage to using imaging devices with long wavelength spectral responsivity. We also expect the most efficient imaging to be near the surface normal where the intensity is greatest; although for contoured surfaces, the relative intensity across the surface may appear to vary due to decreasing Cherenkov intensity with increased angle from the skin normal. This research was supported in part by a GAANN Fellowship from the Department of Education.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Morphology, electrical, and optical properties of heavily doped ZnTe:Cu thin films

We report on a study of the physical properties of ZnTe:Cu films with Cu content up to ∼12 at. % prepared using rf magnetron sputtering. The composition and lateral homogeneities are studied using X-ray photoelectron spectroscopy (XPS). Atomic force microscopy measurements on films deposited at different substrate temperatures (up to 325 °C) yielded activation energy of 12 kJ/mole for the grains growth. The results of XPS and electrical and optical measurements provide evidence for the formation of the ternary zinc copper telluride alloy in films containing Cu concentration above ∼4 at. %. The XPS results suggest that copper is incorporated in the alloy with oxidation state Cu{sup 1+} so that the alloy formula can be written Zn{sub 1−y}Cu{sub y} Te with y = 2−x, where x is a parameter measuring the stoichiometry in the Cu site. The formation of this alloy causes appreciable shift in the binding energies of the XPS peaks besides an IR shift in the energy band gap. Detailed analysis of the optical absorption data revealed the presence of two additional transitions, besides the band gap one, originating from the Γ{sub 8} and Γ{sub 7} (spin-orbit) valence bands to a donor level at ∼0.34 eV below the Γ{sub 6} conduction band. This interpretation yields a value for the valence band splitting energy Δ≅ 0.87 eV independent of copper concentration. On the other hand, the mechanism of formation of the alloy is tentatively explained in terms of a point defect reaction in which substitutional Cu defect Cu{sub Zn} is also created. Assuming that substitutional Cu is the dominant acceptor in the Zn rich alloy as in ZnTe, its formation energy was determined to be 1.7 eV close to the theoretical value (1.41 eV) in ZnTe.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Er{sup 3+}-doped strontium lithium bismuth borate glasses for broadband 1.5 {mu}m emission - optical properties

Strontium lithium bismuth borate glasses (SLBiB) doped with various concentrations of Er{sup 3+} were prepared using conventional melt quench technique and investigated their optical properties. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction and SEM analysis. Optical properties were studied by measuring the optical absorption and near infrared luminescence spectra at room temperature. Judd-Ofelt (J-O) theory has been applied for the f.f transitions of Er{sup 3+} ions to evaluate J-O intensity parameters, {Omega}{lambda} ({lambda} = 2, 4 and 6). Using the J-O intensity parameters, radiative properties such as transition probabilities (A{sub R}), branching ratios ({beta}) and radiative lifetimes ({tau}) are estimated for certain transitions. From the emission spectra, peak emission-cross sections ({sigma}{sub p}) and products of stimulated emission cross-section and full width at half maximum ({sigma}{sub p} Multiplication-Sign FWHM) were calculated for the observed emission transition, {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2}.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Many-body enhancement of high-harmonic generation in monolayer MoS2

Abstract Many-body effects play an important role in enhancing and modifying optical absorption and other excited-state properties of solids in the perturbative regime, but their role in high harmonic generation (HHG) and other nonlinear response beyond the perturbative regime is not well-understood. We develop here an ab initio many-body method to study nonperturbative HHG based on the real-time propagation of the non-equilibrium Green’s function with the GW self energy. We calculate the HHG of monolayer MoS 2 and obtain good agreement with experiment, including the reproduction of characteristic patterns of monotonic and nonmonotonic harmonic yield in the parallel and perpendicular responses, respectively. Here, we show that many-body effects are especially important to accurately reproduce the spectral features in the perpendicular response, which reflect a complex interplay of electron-hole interactions (or exciton effects) in tandem with the many-body renormalization and Berry curvature of the independent quasiparticle bandstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Rational Design of Dithienopicenocarbazole-Based Dyes and a Prediction of Their Energy-Conversion Efficiency Characteristics for Dye-Sensitized Solar Cells

Here, a series of metal-free organic donor-acceptor (D-A) derivatives (ME01-ME06) of the known dye C281 were designed using first principles calculations in order to evaluate their potential for applications in dye-sensitized solar cells (DSSCs). Their physical and electronic properties were calculated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). These include molecular properties that are required to assess the feasibility of a dye to function in DSSCs: UV/vis absorption spectra, light-harvesting efficiency (LHE), and driving forces of electron injection (Δ G inj ). ME01, ME02, and ME04 are predicted to exhibit broad absorption optical spectra that cover the entire visible range, rendering these three dyes promising DSSC prospects. Device-relevant calculations on these three short-listed dyes and the parent dye C281 were then performed, whereupon the dye molecules were adsorbed onto anatase TiO 2 surfaces to form the DSSC working electrode. Associated DSSC device characteristics of this dye…TiO 2 interfacial structure were determined. These include the light-harvesting efficiency, the number of injected electrons, the electron-injection lifetime, and the quantum energy alignment of the adsorbed dye molecule to that of its device components. In turn, these calculated parameters enabled the derivation of the DSSC device performance parameters: short-circuit current density, J SC , incident photon-to-electron conversion efficiency, IPCE, and open-circuit voltage, V OC . Thus, we demonstrate a systematic ab initio approach to screen rationally designed D-A dyes with respect to their potential applicability in high-performance DSSC devices.

14 SOLAR ENERGY↗
DOE OSTI2025

Electronic structure and exchange interactions in altermagnetic MnGeP 2 in the quasiparticle self-consistent G W approach

The quasiparticle self-consistent 𝐺⁡𝑊 method is used to study the electronic band structure, optical dielectric function, and exchange interactions in chalcopyrite, 𝐼⁢ ‾ 4 ⁢2⁢𝑑, structure MnGeP 2 . The material is found to be an antiferromagnetic semiconductor with a lowest direct gap of 2.44 eV at the Γ point and a lower indirect gap of 1.87 eV from Γ to 𝑀. The material is an altermagnet because the two magnetic atoms of opposite spin are related by a twofold rotation operation perpendicular to the main fourfold rotation inversion axis. The spin splittings along a low symmetry line like 𝑃⁢𝑁 is sizable while at k points on the diagonal mirror planes or on the twofold symmetry axes the spin splitting is zero. The exchange interactions are calculated using a linear response approach. The antiferromagnetic exchange interaction between nearest neighbors in the primitive unit cell is dominating and found to be slightly decreasing upon carrier doping but not sufficiently to change the interaction to become ferromagnetic. The bare (noninteracting) and interacting transverse spin susceptibilities, which provide interatomic site exchange interactions after averaging over the muffin-tin spheres, are calculated from the 𝐺⁡𝑊 band structure and wave functions. From these exchange interactions, the spin wave spectra are obtained along the high symmetry lines and the Néel temperature is calculated using the mean-field and Tyablikov estimations. The dielectric function and the optical absorption spectra are calculated including excitonic effects using the Bethe Salpeter equation. The exchange interactions around Mn Ge defect sites is also studied. While we find it can generate ferromagnetic interactions with neighboring spins, we did not find direct evidence of producing an overall ferromagnetic phase. First, if Mn antisites are introduced by exchanging Mn with a nearby Ge, the interactions stay largely antiferromagnetic. Second, when we add additional Mn, in other words in Mn-rich stoichiometry, the Mn Ge antisites produce a strong ferromagnetic interaction primarily with the Mn in the same basal plane but weaker ferromagnetic interaction with adjacent plane Mn. The interactions between regular lattice Mn stay antiferromagnetic as before and thus favor keeping the antiferromagnetic order along the [001] direction. Adding Mn antisites, however, does lead to a metallic band structure.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Study of surface fluorination of photocatalytic TiO{sub 2} by thermal shock method

Surface fluorinated TiO{sub 2} powders were prepared by thermal shock method and an overall comparative study was achieved on the basis of XRD, SEM, UV-vis and XPS analyses. The main objective was to elucidate the influences of surface fluorination on the crystallite structures, morphologies, optical properties and surface chemistry with the temperature. According to the results, the surface fluorination under thermal shock method below 600 Degree-Sign C did not change the crystallite structure and the particles size, but successfully created chemisorbed fluoride ions, oxygen vacancies and increased the hydroxyl groups on the surface of TiO{sub 2}. The presence of oxygen vacancies was assigned to the red shift of TiO{sub 2} optical absorption edge, which was the origin of visible-light-induced photocatalytic activity of these samples. For the thermal shock temperatures over 600 Degree-Sign C, the K{sub 2}Ti{sub 6}O{sub 13}-like phase was formed, resulting from the decrease of surface hydroxyl groups and the blue shift in absorption edge which reduced the photocatalytic activity. - Graphical abstract: The influence of fluorination on the surface of TiO{sub 2} by thermal shock method at several temperatures has been investigated by following the evolution of the F1s spectra obtained by X-ray photoelectron spectroscopy. The blank peaks are assigned to the chemisorbed fluoride ions on the samples surface and the filled peaks to fluorine atoms in oxygenated environment of solid solution TiO{sub 2-x}F{sub x}, which is originated from the substitution of F ions for O ions in the TiO{sub 2} lattice. Highlights: Black-Right-Pointing-Pointer Surface fluorination of TiO{sub 2} P25 by thermal shock method. Black-Right-Pointing-Pointer Structure, morphology, surface and photocatalytic properties of fluorinated TiO{sub 2}. Black-Right-Pointing-Pointer Low thermal shock temperatures increase the photocatalytic activity. Black-Right-Pointing-Pointer Fluoride ions chemisorbed on the surface without structure and morphology change. Black-Right-Pointing-Pointer Formation of K{sub 2}Ti{sub 6}O{sub 13} phase at high thermal shock temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Spectroscopic investigation of historical uranium glasses

Here, we present spectroscopic investigations of uranium in two historical glasses. A 1920's-1930's Art Deco (Bagley Carnival) green soda-lime-silica uranium glass bowl and a 1930's-1940's (Thomas Webb) yellow full lead crystal uranium glass vase were studied using optical absorption spectroscopy, XRF and SEM-EDX, X-band EPR and High- Energy Resolution Fluorescence-Detected (HERFD)-XANES. Uranium speciation may be different in the two glasses. Uranium occurs as uranyl groups (UO 2 2+ ) with minority reduced uranium species, mostly as U(V), more important in the Webb glass than in the Bagley glass. The differences between the two glasses arise from the fining procedure and result from the presence of other multivalent elements and differences in base glass composition. Electron Paramagnetic Resonance (EPR) spectra show the presence of an incipient signal close to g~2, partially annealed by heating to 550 °C, which we assign to a small concentration of radiation-induced defects caused by uranium decay. The presence of multivalent glass components in addition to U (As + Cu + Fe in the Bagley glass and Sb + Fe in the Webb glass) can trap the electron-hole pairs generated by the presence of uranium. This may explain the weakness of this signal in these glasses that anyway received a limited radiation dose since their fabrication. The low activity of these glasses, close to the background radiation, confirms that there is no danger to exhibiting them in museums.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Spatio-Kinetic Electronic Heterogeneity in MoS 2 Revealed by Ultrafast Electron Microscopy: Implications for Optoelectronics

There is broad interest in layered, two-dimensional (2D) semiconductors owing to their high optical absorption and ability to heterogeneously integrate with various substrates. In such layered semiconductors, mesoscopic imperfections, such as surface step edges, may affect charge carrier kinetics and device performance, but studying their effects on carrier transport with sufficient spatial and temporal resolution is a challenge. Using scanning ultrafast electron microscopy, we image the near-surface charge carrier kinetics with μm/ps spatiotemporal resolution in single-crystal MoS 2 samples with surface steps tens of nanometers in height. We find an approximately 3-fold increase in surface trap density near such surface steps compared to the uniform, flat surface regions. Despite the difference in trap state density, filling of the traps occurs over the same time scale (∼100 ps), but carrier recovery is much slower near the step compared to the uniform regions of the material. Furthermore, these results provide an approach to measure ultrafast dynamics and determine the required uniformity of layered materials depending on the speed limit constraints for specific applications.

SEM↗
DOE OSTI2017

Electronic environments of ferrous iron in rhyolitic and basaltic glasses at high pressure: Silicate Glasses at High Pressure

The physical properties of silicate melts within Earth's mantle affect the chemical and thermal evolution of its interior. Chemistry and coordination environments affect such properties. We have measured the hyperfine parameters of iron-bearing rhyolitic and basaltic glasses up to ~120 GPa and ~100 GPa, respectively, in a neon pressure medium using time domain synchrotron Mössbauer spectroscopy. The spectra for rhyolitic and basaltic glasses are well explained by three high-spin Fe 2+ -like sites with distinct quadrupole splittings. Absence of detectable ferric iron was confirmed with optical absorption spectroscopy. The sites with relatively high and intermediate quadrupole splittings are likely a result of fivefold and sixfold coordination environments of ferrous iron that transition to higher coordination with increasing pressure. The ferrous site with a relatively low quadrupole splitting and isomer shift at low pressures may be related to a fourfold or a second fivefold ferrous iron site, which transitions to higher coordination in basaltic glass, but likely remains in low coordination in rhyolitic glass. These results indicate that iron experiences changes in its coordination environment with increasing pressure without undergoing a high-spin to low-spin transition. We compare our results to the hyperfine parameters of silicate glasses of different compositions. With the assumption that coordination environments in silicate glasses may serve as a good indicator for those in a melt, this study suggests that ferrous iron in chemically complex silicate melts likely exists in a high-spin state throughout most of Earth's mantle.

58 GEOSCIENCES↗
DOE OSTI2019

Energy Coupling Mechanisms and Scaling Behavior Associated with Laser Powder Bed Fusion Additive Manufacturing

In situ optical absorptivity measurements are carried out to clarify the physics of the laser-material interactions involved and to validate both finite element and analytical models describing laser powder bed fusion processing. Absorption of laser energy is evaluated directly using precise calorimetry measurements and compared to melt pool depths for common structural metal alloys (Ti-6Al-4V, Inconel 625, and stainless steel 316L) as a function of incident laser power, scan velocity and laser beam diameter. Changes in both absorptivity and melt pool depths for all materials are found to vary strongly across the conduction-keyhole mode threshold. A hydrodynamic finite element model is coupled to a ray-tracing-based absorptivity model, yielding excellent agreement with the experimental results and elucidating additional physics. The experimental results are further analyzed using normalized enthalpy ( β ) and normalized thermal diffusion length ( L* th ) relations and demonstrate that the normalized melt pool depth ( d* = d/a , where d is melt pool depth and a is beam radius) is proportional to βL* th , while absorptivity follows an asymptotic exponential function against βL* th . Expressions for melt pool depth and laser absorptivity across different materials and laser scan systems are derived and thus provide useful tools to accelerate the optimization of laser processing parameters for metal 3D printing processes.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Solution-Processed Nanoporous Organic Semiconductor Thin Films: Toward Health and Environmental Monitoring of Volatile Markers

Porous materials are ubiquitous in nature and have found a wide range of applications because of their unique absorption, optical, mechanical, and catalytic properties. Large surface-area-to-volume ratio is deemed a key factor contributing to their catalytic properties. Here, it is shown that introducing tunable nanopores (50–700 nm) to organic semiconductor thin films enhances their reactivity with volatile organic compounds by up to an order of magnitude, while the surface-area-to-volume ratio is almost unchanged. Mechanistic investigations show that nanopores grant direct access to the highly reactive sites otherwise buried in the conductive channel of the transistor. The high reactivity of nanoporous organic field-effect transistors leads to unprecedented ultrasensitive, ultrafast, selective chemical sensing below the 1 ppb level on a hundred millisecond time scale, enabling a wide range of health and environmental applications. Flexible sensor chip for monitoring breath ammonia is further demonstrated; this is a potential biomarker for chronic kidney disease.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Efficient Quaternary Organic Solar Cells with Parallel‐Alloy Morphology

Abstract Two compatible donors (PBDB‐T and PTB7‐Th) and two miscible acceptors (ITIC and FOIC) are employed to deliver a parallel‐alloy morphology model in non‐fullerene‐based quaternary organic solar cells. PBDB‐T and PTB7‐Th form a parallel link with a slight adjustment of molecular packing into enhanced face‐on crystallites while ITIC disperses into discontinuous FOIC microcrystal regions to form continuous and ordered alloy‐like acceptor phases. Characterization of blend morphology highlights the parallel‐alloy model—enabled by the introduction of PBDB‐T and ITIC, which contributes to improved molecular packing and reduced domain size resulting in efficient charge generation and consistent transport channels. This successful parallel‐alloy quaternary blend morphology demonstrates an enhanced optical absorption, optimized domain size, and nanostructures toward simultaneous improvement in charge transfer and transport. Therefore, a power conversion efficiency of 12.52% is realized for a quaternary device which is 6% higher than the ternary device (PBDB‐T:PTB7‐Th:FOIC) and 12% higher than the binary device (PTB7‐Th:FOIC). Domination of quaternary devices over ternary and binary blends, which is another feasible way to realize highly efficient devices through further investigation of quaternary OSCs, is presented.

Bi, Zhaozhao↗
DOE OSTI2021

Impact of Oxygen Non-Stoichiometry on Near-Ambient Temperature Ionic Mobility in Polaronic Mixed-Ionic-Electronic Conducting Thin Films

Enhanced ionic mobility in mixed ionic and electronic conducting solids contributes to improved performance of memristive memory, energy storage and conversion, and catalytic devices. Ionic mobility can be significantly depressed at reduced temperatures, for example, due to defect association and therefore needs to be monitored. Measurements of ionic transport in mixed conductors, however, proves to be difficult due to dominant electronic conductivity. This study examines the impact of different levels of quenched-in oxygen deficiency on the oxygen vacancy mobility near room temperature as measured by a novel dynamic current-voltage analysis. A Pr 0.1 Ce 0.9 O 2-δ film was grown by pulsed laser deposition and subsequently annealed, from 400-600° C, in various oxygen partial pressures to modify its oxygen vacancy concentration while minimizing microstructural growth and cation segregation. To monitor changes in film non-stoichiometry, we leverage the existence of an optical absorption center, related to the oxidation state of Pr ions in Pr0.1Ce0.9O2-δ. The oxygen vacancy migration enthalpy was found to exhibit a small increase from 0.73± 0.04 to 0.79 ± 0.02 eV with increasing oxygen deficiency, while the pre-factor was found to increase by a factor of 135. Here, a nearly 13-fold increase in ionic mobility at 60 °C for increases in oxygen non-stoichiometry from 0.032 ± 0.001 to 0.042± 0.001 was thereby detected. Raman spectroscopy was employed to rule out changes in strain as the primary cause for the significant change in mobility. Several factors potentially contributing to the large pre-factor changes are examined and discussed. Insights into how ionic defect concentration can markedly impact ionic mobility should help in elucidating the origins of variations seen in nanoionic devices.

36 MATERIALS SCIENCE↗