scholarly journals The Optical Blueshift Saturation Behavior of Mg-=SUB=-x-=/SUB=-Zn-=SUB=-1-x-=/SUB=-O Films

2021 ◽  
Vol 63 (10) ◽  
pp. 1484
Author(s):  
C. Xue ◽  
J. Zhang ◽  
X. Lu ◽  
M. Geng ◽  
T. Huang ◽  
...  
Keyword(s):  
Structural Disorder ◽  
X Ray Diffraction ◽  
Band Tail ◽  
X Ray ◽  
Competition Mechanism ◽  
Band Engineering ◽  
Alloy Semiconductors ◽  
Microscopy Images ◽  
Deposition Technology ◽  
Disordered Alloy

A phenomenon of blueshift saturation was observed from cathodoluminescence (CL) spectra of MgxZn1-xO films (0.069≤x≤0.8) which were grown by pulsed laser deposition technology. By analyzing the results of composition-dependent X-ray diffraction spectra, scanning electron microscopy images, absorption spectra and CL spectra, the crystalline structural disorder was determined via Urbach energy value. Furthermore, a competition mechanism between band-filling effect and band tail states was proposed in the composition-dependent CL spectra. This competition is believed to be responsible for the composition-induced blueshift saturation often observed in the disordered alloy semiconductors. The results of this research can provide important reference in energy-band engineering.

Structural Properties Of Co/Re Superlattices

1991 ◽  
Vol 238 ◽  
Author(s):  
Y. Huai ◽  
R. W. Cochrane ◽  
Y. Shi ◽  
H. E. Fischer ◽  
M. Sutton
Keyword(s):  
Structural Disorder ◽  
Multilayer Films ◽  
Film Plane ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bilayer Films ◽  
Out Of Plane ◽  
Reflectivity Data ◽  
Sharp Interfaces ◽  
Good Agreement

ABSTRACTThe structures of equal-thickness Co/Re multilayer films and several Co/Re bilayer films have been investigated by X-ray diffraction at low and high angles. Analysis of low-angle reflectivity data from bilayer films indicates that interfacial intermixing is limited to three monolayers and that the two interfacial configurations are different. The high-angle X-ray diffraction data show that multilayer films have coherent interfaces and a highly textured structure with hep [002] orientations normal to the film plane for periods 21 Å ≤ Λ ≤220 Å. Detailed structures have been determined by fitting the X-ray spectra to calculated ones using a trapezoidal model. The results indicate that samples with 42 Å≤ Λ ≤220 Å have relatively sharp interfaces, in good agreement with the bilayer results. In addition, an out-of-plane expansion of the Co (002) layer is observed in samples with large Λ and results from structural disorder leading to a reduced atomic density. For Λ <21 Å the interfaces arise from the rougher surfaces of the deposited layers.

Facile Refluxing Synthesis of Hydroxyapatite Nanoparticles

2015 ◽  
Vol 68 (8) ◽  
pp. 1293 ◽  
Author(s):  
Pakvipar Chaopanich ◽  
Punnama Siriphannon
Keyword(s):  
Crystallite Size ◽  
Reaction Times ◽  
Single Step ◽  
Hydroxyapatite Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Aqueous Mixture ◽  
Diffraction Patterns ◽  
Microscopy Images

Hydroxyapatite (HAp) nanoparticles were successfully synthesized from an aqueous mixture of Ca(NO3)2·4H2O and (NH4)2HPO4 by a facile single-step refluxing method using polystyrene sulfonate (PSS) as a template. The effects of reaction times, pH, and PSS concentration on the HAp formation were investigated. It was found that the crystalline HAp was obtained under all conditions after refluxing the precursors for 3 and 6 h. The longer refluxing time, the greater the crystallinity and the larger the crystallite size of the HAp nanoparticles. The HAp with poor crystallinity was obtained at pH 8.5; however, the well-crystallized HAp was obtained when reaction pH was increased to 9.5 and 10.5. In addition, the X-ray diffraction patterns revealed that the presence of PSS template caused the reduction of HAp crystallite size along the (002) plane from 52.6 nm of non-template HAp to 43.4 nm and 41.4 nm of HAp with 0.05 and 0.2 wt-% PSS template, respectively. Transmission electron microscopy images of the synthesized HAp revealed the rod-shaped crystals of all samples. The synthesized HAp nanoparticles were modified by l-aspartic acid (Asp) and l-arginine (Arg), having negative and positive charges, respectively. It was found that the zeta potential of HAp was significantly changed from +5.46 to –24.70 mV after modification with Asp, whereas it was +4.72 mV in the Arg-modified HAp. These results suggested that the negatively charged amino acid was preferentially adsorbed onto the synthesized HAp surface.

Gallium-containing Heusler phases ScRh2Ga, ScPd2Ga, TmRh2Ga and LuRh2Ga – magnetic and solid state NMR-spectroscopic characterization

2017 ◽  
Vol 72 (8) ◽  
pp. 609-615
Author(s):  
Lukas Heletta ◽  
Stefan Seidel ◽  
Christopher Benndorf ◽  
Hellmut Eckert ◽  
Rainer Pöttgen
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Spectroscopic Characterization ◽  
Structural Disorder ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Phase Purity ◽  
X Ray ◽  
Arc Melting ◽  
Pauli Paramagnetism

AbstractThe gallium-containing Heusler phases ScRh2Ga, ScPd2Ga, TmRh2Ga and LuRh2Ga have been synthesized by arc-melting of the elements followed by different annealing sequences to improve phase purity. The samples have been studied by powder X-ray diffraction. The structures of Lu0.97Rh2Ga1.03 (Fm3̅m, a=632.94(5) pm, wR2=0.0590, 46 F2 values, seven variables) and Sc0.88Rh2Ga1.12 (a=618.91(4) pm, wR2=0.0284, 44 F2 values, six variables) have been refined from single crystal X-ray diffractometer data. Both gallides show structural disorder through Lu/Ga and Sc/Ga mixing. Temperature dependent magnetic susceptibility measurements showed Pauli paramagnetism for ScRh2Ga, ScPd2Ga, and LuRh2Ga and Curie-Weiss paramagnetism for TmRh2Ga. 45Sc and 71Ga solid state MAS NMR spectroscopic investigations of the Sc containing compounds confirmed the site mixing effects typically observed for Heusler phases. The data indicate that the effect of mixed Sc/Ga occupancy is significantly stronger in ScRh2Ga than in ScPd2Ga.

Effects of Indium Incorporation on the Optical Properties of ZnO Films

2006 ◽  
Vol 11-12 ◽  
pp. 159-162 ◽  
Author(s):  
Yong Ge Cao ◽  
Lei Miao ◽  
Sakae Tanemura ◽  
Yasuhiko Hayashi ◽  
Masaki Tanemura
Keyword(s):  
Optical Transmission ◽  
Full Width Half Maximum ◽  
Structural Disorder ◽  
Band Gaps ◽  
Zno Films ◽  
Photoluminescence Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optical Band Gaps ◽  
Xrd Patterns

Transparent indium-doped ZnO (IZO) films with low In content (<6at%) were fabricated through radio-frequency (rf) helicon magnetron sputtering. Formation of In-Zn-O solid solution was confirmed by X-ray diffraction (XRD) patterns. Incorporation of indium into ZnO films enhances the optical transmission in the visible wavelength. The optical band-gaps slightly increase from 3.25eV (ZnO) to 3.28eV (In0.04Zn0.96O) and to 3.30eV (In0.06Zn0.94O) due to Burstain-Moss effect. The Urbach tail parameter E0, which is believed to be a function of structural disorder, increases from 79meV (ZnO), to 146meV (In0.04Zn0.96O), and to 173meV (In0.06Zn0.94O), which is consistent with increase of Full-Width Half-Maximum (FWHM) in corresponding XRD patterns. Decreasing in crystal quality with increasing indium concentration is also confirmed by photoluminescence spectra.

scholarly journals Structural and spectroscopic analyses of copper doped P2O5-ZnO-K2O-Bi2O3 glasses

2015 ◽  
Vol 9 (3) ◽  
pp. 169-173 ◽  
Author(s):  
Yahia Elbashar
Keyword(s):  
Optical Band Gap ◽  
Band Gap Energy ◽  
Dielectric Constants ◽  
X Ray Diffraction ◽  
Band Tail ◽  
Absorption Data ◽  
X Ray ◽  
Spectroscopic Analyses ◽  
Acceptable Range ◽  
Prepared Glass

Homogeneous glass samples with different compositions 42(P2O5)?40 (ZnO)?(16?x)(K2O)?2 (Bi2O3)?x(Cu2O) (where x = 1, 2 and 3mol%) were prepared by conventional melt-quenched technique under controlled conditions. The structure of the prepared glass samples was investigated by X-ray diffraction. Optical properties (transmittance and reflectance) of the glasses were measured in the wavelength range 200-900 nm. The optical band gap energy of the investigated glasses with 1, 2 and 3mol% Cu2O was estimated from absorption data using the Mott and Davis relation and found to be 2.33, 2.45 and 2.53 eV, respectively. The mechanism of optical absorption was found to be direct. The band tail width was also estimated and found to lay in the acceptable range. Refractive index, absorption coefficient, extinction coefficient and real/imaginary parts of dielectric constants were calculated. Further to this, some theoretical investigation of the spectral problems was carried out. The investigation was based on finite difference method.

Charge transfer associated with lithium insertion in Mo1−yNbyS2 layered compounds

1984 ◽  
Vol 62 (1) ◽  
pp. 10-14 ◽  
Author(s):  
M. A. Py ◽  
R. R. Haering
Keyword(s):  
Voltage Drop ◽  
Structural Disorder ◽  
Host Lattice ◽  
Layered Compounds ◽  
Electrochemical Cells ◽  
X Ray Diffraction ◽  
Electronic Density ◽  
X Ray ◽  
Critical Composition ◽  
Trigonal Prismatic

The Mo1−yNbyS2 layered compounds form solid solutions. The coordination of the Mo and Nb atoms by S atoms is trigonal prismatic over the entire range of composition, 0 ≤ y ≤ 1. The [Formula: see text] band, separated from the other d-bands by a bandgap of the order of 1 eV, contains y empty states per formula unit. For y ≤ 0.6, Li/LixMo1−yNbyS2 electrochemical cells reveal a sharp voltage drop of V(x) at a critical composition x which is correlated to y by [Formula: see text]. This result clearly establishes the transfer of one electron per intercalated lithium (x ≤ 0.6) to the [Formula: see text] band of the host.Electrochemical cells, made with samples whose X-ray diffraction spectra suggest the presence of structural disorder in the host lattice, show a less abrupt voltage drop near xc, in qualitative agreement with the influence of disorder on the electronic density-of-states distribution N(E) near a band edge. The origin of the voltage drop observed for LixMo0.2Nb0.8S2 is not fully established.

scholarly journals Structural and dynamic aspects related to oligomerization of apo SOD1 and its mutants

2009 ◽  
Vol 106 (17) ◽  
pp. 6980-6985 ◽  
Author(s):  
Lucia Banci ◽  
Ivano Bertini ◽  
Mirela Boca ◽  
Vito Calderone ◽  
Francesca Cantini ◽  
...  
Keyword(s):  
Solvent Accessibility ◽  
Structural Disorder ◽  
Free Form ◽  
X Ray Diffraction ◽  
X Ray ◽  
Conformational Variability ◽  
Metal Free ◽  
Loop Regions ◽  
Lateral Sclerosis ◽  
Apo State

The structural and dynamical properties of the metal-free form of WT human superoxide dismutase 1 (SOD1) and its familial amyotrophic lateral sclerosis (fALS)-related mutants, T54R and I113T, were characterized both in solution, through NMR, and in the crystal, through X-ray diffraction. We found that all 3 X-ray structures show significant structural disorder in 2 loop regions that are, at variance, well defined in the fully-metalated structures. Interestingly, the apo state crystallizes only at low temperatures, whereas all 3 proteins in the metalated form crystallize at any temperature, suggesting that crystallization selects one of the most stable conformations among the manifold adopted by the apo form in solution. Indeed, NMR experiments show that the protein in solution is highly disordered, sampling a large range of conformations. The large conformational variability of the apo state allows the free reduced cysteine Cys-6 to become highly solvent accessible in solution, whereas it is essentially buried in the metalated state and the crystal structures. Such solvent accessibility, together with that of Cys-111, accounts for the tendency to oligomerization of the metal-free state. The present results suggest that the investigation of the solution state coupled with that of the crystal state can provide major insights into SOD1 pathway toward oligomerization in relation to fALS.

scholarly journals Development of 3D Bioactive Scaffolds through 3D Printing Using Wollastonite–Gelatin Inks

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2420 ◽  
Author(s):  
Filis Curti ◽  
Izabela-Cristina Stancu ◽  
Georgeta Voicu ◽  
Horia Iovu ◽  
Cristina-Ioana Dobrita ◽  
...  
Keyword(s):  
3D Printing ◽  
Bone Repair ◽  
Homogeneous Distribution ◽  
Orthopedic Trauma ◽  
Fish Gelatin ◽  
Mass Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bioactive Scaffolds ◽  
Microscopy Images

The bioactivity of scaffolds represents a key property to facilitate the bone repair after orthopedic trauma. This study reports the development of biomimetic paste-type inks based on wollastonite (CS) and fish gelatin (FG) in a mass ratio similar to natural bone, as an appealing strategy to promote the mineralization during scaffold incubation in simulated body fluid (SBF). High-resolution 3D scaffolds were fabricated through 3D printing, and the homogeneous distribution of CS in the protein matrix was revealed by scanning electron microscopy/energy-dispersive X-ray diffraction analysis (SEM/EDX) micrographs. The bioactivity of the scaffold was suggested by an outstanding mineralization capacity revealed by the apatite layers deposited on the scaffold surface after immersion in SBF. The biocompatibility was demonstrated by cell proliferation established by MTT assay and fluorescence microscopy images and confirmed by SEM micrographs illustrating cell spreading. This work highlights the potential of the bicomponent inks to fabricate 3D bioactive scaffolds and predicts the osteogenic properties for bone regeneration applications.

Single-molecule precursor-based approaches to cobalt sulphide nanostructures

2010 ◽  
Vol 368 (1927) ◽  
pp. 4249-4260 ◽  
Author(s):  
Karthik Ramasamy ◽  
Weerakanya Maneerprakorn ◽  
Mohammad A. Malik ◽  
Paul O'Brien
Keyword(s):  
Electron Microscopy ◽  
Single Molecule ◽  
Size Range ◽  
Hexagonal Phase ◽  
Cobalt Complexes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Cobalt Sulphide ◽  
Microscopy Images

Cobalt complexes of 1,1,5,5-tetramethyl-2,4-dithiobiuret, [Co{N(SCNMe 2 ) 2 } 3 ] ( 1 ), and 1,1,5,5-tetraisopropyl-2-thiobiuret, [Co{N(SOCN i Pr 2 ) 2 } 2 ] ( 2 ), have been synthesized and characterized. Both complexes were used as single-molecule precursors for the preparation of cobalt sulphide nanoparticles by thermolysis in hexadecylamine, octadecylamine or oleylamine. The powder X-ray diffraction pattern of as-prepared nanoparticles showed the hexagonal phase of Co 1− x S from complex 1 and mixtures of cubic and hexagonal Co 4 S 3 from complex 2 . Transmission electron microscopy images of material prepared from complex 1 showed spherical and trigonally shaped particles in the size range of 10–15 nm; whereas spheres, rods, trigonal prisms and pentagonally and hexagonally faceted crystallites were observed from complex 2 . This observation is the first of the Co 4 S 3 phase in a nanodispersed form.

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