pinecone/core-2020-05-10-deduplication huggingface dataset:
Soft X-ray induced oxidation on acrylic acid grafted luminescent silicon quantum dots in ultrahigh vacuum

Water soluble acrylic acid grafted luminescent silicon quantum dots (Si-QDs) were prepared by a simplified method. The resulting Si-QDs dissolved in water and showed stable strong luminescence with peaks at 436 and 604?nm. X-ray photoelectron spectroscopy (XPS) was employed to examine the surface electronic states after the synthesis. The co-existence of the Si2p and C1s core levels infers that the acrylic acid has been successfully grafted on the surface of silicon quantum dots. To fit the Si2p spectrum, four components were needed at 99.45, 100.28, 102.21 and 103.24?eV. The first component at 99.45?eV (I) was assigned to Si–Si within the silicon core of the Si-QDs. The second component at 100.28?eV (II) was from Si–C. The third at 102.21?eV (III) was a sub-oxide state and the fourth at 103.24?eV (IV) was from SiO2 at Si-QDs surface. With an increase in exposure to soft X-ray photons, the intensity ratio of the two peaks within the Si2p region A and B increased from 0.5 to 1.4 while the peak A intensity decreased, and eventually a steady state was reached. This observation is explained in terms of photon-induced oxidation taking place within the surface dangling bonds. As the PL profile for Si-QDs is influenced by the degree of oxidation within the nanocrystal structure, the inducement of oxidation by soft X-rays will play a role in the range of potential applications where such materials could be used – especially within biomedical labelling
Structure and electrical properties in the K1/2Bi1/2TiO3-K1/2Bi1/2ZrO3 solid solution (KBT-KBZ)

International audienceThe present work is devoted to the study of the Zr 4þ /Ti 4 substitution in the K1/2Bi1/2Ti(1-x)ZrxO3 solid solution (x ¼ 0.0 to x ¼ 1.0), based upon the K1/2Bi1/2TiO3 (KBT) ferroelectric compound. The tetragonal distortion of KBT is suppressed by this substitution and leads to the cubic compound K1/2Bi1/2ZrO3 (KBZ). These results agree with the values of the ionic radii of the Zr 4þ and Ti 4 ions (rTi 4þ ¼ 0.605 A˚ and rZr 4þ ¼ 0.72 A˚ ). Close to KBT (x 0.05), the symmetry remains tetragonal. For higher values of x, the ''a'' lattice parameter (cubic indexing) follows Vegard's law, thus conﬁrming the formation of a solid solution. The transformation from tetragonal to cubic proceeds via an intermediate pseudocubic symmetry (0.1 x < 0.5), for which the X-ray diffraction peaks present small broadening and asymmetry. For x 0.5 and up to the KBZ compound (a 4.158 A˚ ), the samples are cubic but some extra peaks are also observed, indicating the occurrence of a secondary phase. The microstructure shows ﬁne-grained ceramic samples for the ﬁrst range, while for the KBZ-rich range the grains are micrometer-sized and associated to very small grains of the secondary phase. Piezoelectricity is observed for the tetragonal and pseudocubic range, the substitution quickly reducing the piezoelectric properties. The measurement of the dielectric properties revealed close to KBT a dielectric anomaly probably associated to the tetragonal-cubic phase transition. For thepseudocubic and cubic range, a broad dielectric anomaly is observed around 300 8C, corresponding to a relaxor behavior
Preparation of Al‐doped ZnO films by aqueous solution process using a continuous circulation reactor

The fabrication of Al‐doped ZnO films by an aqueous solution process using a continuous circulation reactor was studied. By heating ZnO‐saturated ammonia solutions containing 2–10 mM Al(NO₃)₃ with pH 10.7 at 90 ℃ under ambient pressure, polycrystalline ZnO films with Al content of 1–2 at.% were deposited. The carrier concentration of ZnO films increased with increasing Al content, indicating that Al was successfully incorporated into the ZnO crystals. The Al‐doped ZnO films had carrier concentrations of 10¹⁹–10²º cm⁻³ and mobilities of 0.7–7 cm²/V/s after annealing at 300 ℃ in air
Magnetotransport study on AllnN/(GaN)/AIN/GaN heterostructures

Cataloged from PDF version of article.We report the effect of a thin GaN (2?nm) interlayer on the magnetotransport properties of AlInN/AlN/GaN-based heterostructures. Two samples were prepared (Sample A: AlInN/AlN/GaN and sample B: AlInN/GaN/AlN/GaN). Van der Pauw and Hall measurements were performed in the 1.9300?K temperature range. While the Hall mobilities were similar at room temperature (RT), sample B had nearly twice as large Hall mobility as sample A at the lowest temperature; 679 and 889?cm2/Vs at RT and 1460 and 3082?cm2/Vs at 1.9?K for samples A and B. At 1.910?K, the longitudinal magnetoresistance was measured up to 9?T, in turn revealing Shubnikovde Haas (SdH) oscillations. The carrier concentration, effective mass and quantum mobility of the two-dimensional electron gas (2DEG) were determined from SdH oscillations. At 1.9?K, the 2DEG concentration of sample B was nearly seven times larger than of sample A (1.67 x 10(13)/cm2 vs. 0.24 x 10(13)/cm2). On the contrary, the quantum mobility was changed adversely nearly three times (sample B 2500?cm2/Vs and sample A 970?cm2/Vs). The increase of the 2DEG concentration was attributed to the existence of the GaN interlayer, which has strengthened the spontaneous polarization difference between the AlInN and GaN layers of the heterostructure. Hence, the stronger electric field at the 2DEG region bent the conduction band profile downwards and consequently the quantum mobility decreased due to the increased interface roughness scattering
Lattice tilt, concentration, and relaxation degree of partly relaxed InGaAs/GaAs structures

The series of samples is investigated to verify the validity of the
scattering theory within the layers of different relaxation
degree. The samples composed of In0.06Ga0.94As layer of
different thicknesses on GaAs [001] substrates were grown
using MBE technique. The symmetric and asymmetric
reciprocal space maps (RSM) were measured and simulated
for the samples with the fully coherent layer, in the vicinity of
the critical thickness of relaxation, and with the fully relaxed
layer. The crystallographic layer miscuts, indium concentrations,
the relaxation degrees, and density of dislocations have
been precisely evaluate
Nanostructuring and Ge redistribution in thin films of Silicon-Germanium by thermal oxidation

Despite the fact that germanium played a significant role in the advent of modern electronics, silicon-germanium alloys have not been used or studied nearly as extensively as silicon. However, a recent resurgence in industrial and research interest in silicon-germanium ensures that it will have an increasingly important role in nano- and opto-electronics. It is unavoidable that a sound understanding of the oxidation of silicon-germanium will be required as processes are developed for using the material in electronic applications. In fact, a profound appreciation for the oxidation kinetics of silicon-germanium could itself create new applications for the material.
The present work investigates the use of thermal oxidation in nanostructuring of epitaxially grown silicon-germanium by examining the kinetics of oxidation and the redistribution of germanium at the oxidation interface. This is done for oxidations in dry O2 ambients with a particular focus on the influence of temperature and crystalline orientation on the post-oxidation germanium distribution. Physical characterization by x-ray diffraction and variable angle spectroscopic ellipsometry is used along with diffusion and oxidation modeling to derive a series of relations to describe the germanium content and layer thicknesses for the multiple layers created by oxidation. Both modeling and experimental results reveal that the germanium content at the oxidation front is strongly dependent on the oxidation temperature and only weakly dependent on the germanium content in the as-grown silicon-germanium layer. Evidence is presented showing that a decrease, rather than an increase, in the germanium content at the oxidation front may be achieved under certain conditions. The germanium content at the oxidation interface is used to discuss the potential for germanium to act as a catalyst or inhibitor for oxidation of silicon-germanium alloys. Taken together, germanium redistribution by thermal oxidation and the empiric relations presented here may be used to design process recipes for fabrication of nanostructures for nano- and opto-electronic applications
Doping of Si nanoparticles: the effect of oxidation

The preferred location of boron and phosphorus in oxidized free-standing Si
nanoparticles was investigated using a first-principles density functional
approach. The calculated formation energies indicate that P should segregate to
the silicon core, whereas B is equally stable in the Si and SiO_2 regions. Our
models thus suggest that, in contrast with nanocrystals with H-terminated
surfaces, the efficiency of phosphorus incorporation in oxidized Si
nanoparticles can be improved by thermal annealing
Effects of (HoxIn1-x)1.9Sn0.1O3 matrix on magnetization of dispersed Fe3O4 nanocrystals

Solid solutions (HoxIn1−x)1.9Sn0.1O3 with x = 0–0.3 were synthesized to employ as dispersion matrix for oleic acid coated Fe3O4 nanocrystals (NCs). The x = 0.05 matrix exhibited a resistance minimum at a non-zero temperature in each temperature dependent resistivity with magnetic fields of 0 and 1 T, and a negative magnetoresistance. The sample of oleic acid coated Fe3O4 NCs dispersed in the x = 0.05 matrix showed enhanced spontaneous magnetization as the factor of ≈1.3 relative to as-synthesized oleic acid coated Fe3O4 NCs
Non-Ohmic Phenomena in Mn-doped BaTiO3

We report here a novel effect in which the resistance of a semiconducting oxide ceramic increases on application of a small dc bias. The ceramic conducts at high temperatures by an n-type hopping mechanism. On application of a dc bias, conduction electrons are trapped at surface states and the resistance increases. On removal of the dc bias, the trapped electrons are released and the sample regains its original state. This effect is the mirror image of that seen with similar ceramics that conduct by a p-type mechanism whose resistance decreases reversibly on application of a small dc bias. These two phenomena together offer the possibility of novel switching devices and memristive applications, especially if the switching times can be reduced
Spatial heterogeneity of piezoelectric properties in fatigued lead zirconate titanate ceramics

A spatial non-uniformity of the switching properties during the fatigue cycling in lead zirconate titanate ceramics was investigated by a quasi-static piezoelectric and a polarization switching measurements. The agreement between the local piezoelectric properties and the switching behavior of segmented samples was demonstrated. The observed spatial variation of the properties and its evolution with cycle number provides clear evidence of the presence of heterogeneous regions that possess a local fatigue state and the local switching behavior. These results can be explained as a result of the build-up of the spatially non-uniform field and the formation of frozen domains in the ceramics during cycling. The statistical analysis of spatial variation of the switching properties and its evolution with cycle number provides the evidence that the heterogeneity of the switching properties during the fatigue cycling in lead zirconate titanate ceramics is mostly related to the non-uniform change of the local characteristic switching time. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Getting back to Na_xCoO_2: spectral and thermoelectric properties

Sodium cobaltate Na_xCoO_2 as dopable strongly correlated layered material
with a triangular sublattice still poses a challenging problem in condensed
matter. The intriguing interplay between lattice, charge, spin and orbital
degrees of freedom leads to a complex phase diagram bounded by a nominal Mott
(x=0) regime and a band-insulating (x=1) phase. By means of the charge
self-consistent density functional theory (DFT) plus dynamical mean-field
theory (DMFT) scheme, built on a pseudopotential framework combined with a
continuous-time quantum Monte-Carlo solver, we here study the one-particle
spectral function A(k,\omega) as well as the thermopower S(T). The computations
may account for the suppression of the e_g' pockets in A(k,\omega) at lower
doping in line with photoemission experiments. Enhancement of the thermopower
is verified within the present elaborate multi-orbital method to treat
correlated materials. In addition, the two-particle dynamic spin susceptibility
\chi_s(\omega,q) is investigated based on a simplified tight-binding approach,
yet by including vertex contributions in the DMFT linear response. Besides the
identification of paramagnon branches at higher doping, a prominent high-energy
antiferromagnetic mode close to x=0.67 is therewith identified in
\chi_s(\omega,q), which can be linked to extended hopping terms on the CoO_2
sublattice
Electrical properties of CuI films prepared by spin coating

Thin films of cuprous iodide (CuI), which is expected to be used in solid‐state dye‐sensitized solar cells as a hole conductor, were formed by spin coating and subsequent annealing. The effects of the annealing conditions on the electrical properties of the CuI films were investigated by resistivity and Hall‐effect measurements. The CuI films showed p‐type conduction with resistivities of 0.3–5 Ω cm, carrier concentrations of 1 × 10¹⁸–1 × 10¹⁹ cm⁻³ and mobilities of 0.5–2 cm² V⁻¹. It was found that the resistivities of the films annealed in air were slightly lower than those annealed in an Ar atmosphere because the carrier concentrations were higher in the former than in the latter. An increase in the mobility with the rise of annealing temperature was observed in the films annealed in Ar. However, annealing in air at high temperatures oxidized CuI to CuO
The nano-mechanics and magnetic properties of high moment synthetic antiferromagnetic particles

This is an Open Access Article. It is published by WILEY-VCH Verlag GmbH & Co. KGaA.With nanomagnets increasingly being used and proposed as functional units for in vivo applications, it is vital to understand how to optimize their structure, geometry, and size, and their responses to electromagnetic stimulation. Herein, we predicate how to do so for synthetic antiferromagnetic structures that are subjected to external magnetic control. Because the structures are on the scale of biological entities, interactions with cells and molecular constituents can be extreme and careful design must be undertaken to avoid detrimental effects. Thus, the magnetic responses of multilayers, as demonstrated in experiments by Koh et al. [e.g., Hu et al., Adv. Mater. 20, 1479 (2008) and Koh et al., J. Appl. Phys. 107, 09B522 (2010)], are understood using a fully dynamical investigation based on Landau–Lifshitz–Gilbert equations. We find that during the fabrication of the structures the axial positions of the nanomagnets become offset from each other, leading to the characteristic magnetic hysteresis shapes witnessed. We then find the magnetic nano-mechanical forces generated by such structures
Non-ideal memristors for a non-ideal world

Memristors have pinched hysteresis loops in the $V-I$ plane. Ideal memristors
are everywhere non-linear, cross at zero and are rotationally symmetric. In
this paper we extend memristor theory to produce different types of
non-ideality and find that: including a background current (such as an ionic
current) moves the crossing point away from zero; including a degradation
resistance (that increases with experimental time) leads to an asymmetry;
modelling a low resistance filament in parallel describes triangular $V-I$
curves with a straight-line low resistance state. A novel measurement of
hysteresis asymmetry was introduced based on hysteresis and it was found that
which lobe was bigger depended on the size of the breaking current relative to
the memristance. The hysteresis varied differently with each type of
non-ideality, suggesting that measurements of several device I-V curves and
calculation of these parameters could give an indication of the underlying
mechanism.Comment: 18 pages, 12 figures, journal pape
Atomic Layer Deposited Zinc Oxide as Tunable Uncooled Infrared Microbolometer Material

Cataloged from PDF version of article.ZnO is an attractive material for both electrical and optical applications due to its wide bandgap of 3.37eV and tunable electrical properties. Here, we investigate the application potential of atomic-layer-deposited ZnO in uncooled microbolometers. The temperature coefficient of resistance is observed to be as high as -10.4%K-1 near room temperature with the ZnO thin film grown at 120 degrees C. Spectral noise characteristics of thin films grown at various temperatures are also investigated and show that the 120 degrees C grown ZnO has a corner frequency of 2kHz. With its high TCR value and low electrical noise, atomic-layer-deposited (ALD) ZnO at 120 degrees C is shown to possess a great potential to be used as the active layer of uncooled microbolometers. The optical properties of the ALD-grown ZnO films in the infrared region are demonstrated to be tunable with growth temperature from near transparent to a strong absorber. We also show that ALD-grown ZnO can outperform commercially standard absorber materials and appears promising as a new structural material for microbolometer-based applications
RuS2 thin films as oxygen evolving electrocatalyst  Highly oriented growth on single crystal FeS2 substrate and their properties compared to polycrystalline layers

The compound semiconductor RuS2, known as mineral laurite, has been investigated as a potential  photo electrochemically active anode material for the oxygen evolution in the process of  photo electrolytic water splitting. The contribution describes for the first time the preparation of RuS2 thin films deposited on  100   and  111  oriented FeS2  pyrite  substrates using reactive magnetron sputtering. The epitaxial growth of 60 nm thick films was confirmed by X ray diffractometry, texture measurements and the evaluation of cross section trans mission electron micrographs. By optical reflectance spectroscopy and Seebeck coefficient measurements a direct band gap of 1.9 eV and p type conductivity could be determined. Due to the modest electrochemical stability of the epitaxial layers in electrochemical investiga tions, polycrystalline films of laurite were also deposited on Ti sheets and Si wafers. As a function of grain size, [S] [Ru] ratio and grain orientation highest activity towards oxygen evolution was found when the conditions were fulfilled that the layer composition was close to stoichiometry and increased particle sizes showed a strong textured in the grains. Some structural and chemical properties argue for the  100  surface as catalytically active and stable layer compared to other surface
Large Stokes shift downshifting Eu(III) films as efficiency enhancing UV blocking layers for dye sensitized solar cells

Large Stokes shift downshifting organolanthanide complex, Eu(tta)(3)phen, is examined for inclusion in polymeric layers to replace the UV blocking layer in dye sensitized solar cell (DSSC) technology. The UV blocking layer increases stability but power conversion efficiency decreases as incident UV photons are not converted into photocurrent. Eu(tta) 3phen doped polymeric film are prepared and attached to DSSC devices following optimized thickness and concentration from a ray-trace numerical model for the specific DSSC. External quantum efficiency is significantly increased in the UV spectral region compared to DSSCs utilizing a passive, non-luminescent, UV-BL. High Eu(tta)(3)phen film transparency in the visible range minimizes DSSC EQE losses at visible wavelengths. Short-circuit current (I-sc) enhancement due to downshifting is demonstrated (similar to 1%) in small-scale DSSC prototypes, where the specific geometry limits the photon collection efficiency and overall enhancement. Model predictions indicate that 2%-3% I-sc enhancement is realizable in flexible single DSSC compared to, non-luminescent, UV-BL. Added to this, in outdoor conditions taking into account diffuse light, the increment in Isc can increase 50% more. Although photostability of the blended LSS-DS polymer films is not sufficient to be useful for medium-long term outdoor PV applications, the results demonstrate that significant efficiency enhancement can be realized. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimPeer ReviewedPostprint (author’s final draft
Morphological control of band offsets for transparent bipolar heterojunctions:The Bädeker diode

Cuprous iodide is an important transparent p-type semiconductor, it has an illustrious history, and has recently enjoyed a renaissance. In this work, we investigate the electronic band structure and absolute electron energies of the three major known phases of CuI, zincblende (F43m), wurtzite (P63mc), and rock salt (Fm-3m). We also consider CdO, an important n-type transparent semiconductor in these three phases, in order to assess the possibility of constructing transparent bipolar heterojunctions from the two materials. We calculate the relative stability of all three phases of both materials, demonstrating that all three phases should be accessible through non-equilibrium growth techniques. We then calculate the band structures of all six phases, as well as the absolute electron energies (ionization potentials and electron affinities). Thus, we are able to construct energy band alignment diagrams between the materials in the three different structures. These diagrams reveal that one can achieve type-I, type-II, or type-III offsets depending on the crystal structure of the materials. We consider possible applications opened up by these findings
TEM study of defects versus growth orientations in heavily boron-doped diamond

International audienceHeavy boron-doping layer in diamond can be responsible for the generation of extended defects during the growth processes (Blank et al., Diam. Relat. Mater. 17, 1840 (2008) [1]). As claimed recently (Alegre et al., Appl. Phys. Lett. 105, 173103 (2014) [2]), boron pair interactions rather than strain-related misfit seems to be responsible for such dislocation generation. In the present work, electron microscopy observations are used to study the defects induced by heavy boron doping in different growth plane orientations. Facets of pyramidal Hillocks (PHs) and pits provide access to non-conventional growth orientations where boron atoms incorporation is different during growth. TEM analysis on FIB prepared lamellas confirm that also for those growth orientations, the generation of dislocations occurs within the heavily boron-doped diamond layers. Stacking faults (SFs) have been also observed by high resolution transmission electron microscopy (HREM). From the invisibility criteria, using weak beam (WB) observation, ½ [1-10] and 1/6 [11-2], Burger vectors have been identified. Their generation behavior confirms the mechanism reported by Alegre et al. where local in-plane strain effects induced at the growing surface of the diamond lattice by the neighboring of several boron atoms cause the generation of such extended defects