Porous calcium niobate nanosheets prepared by an exfoliation–restacking route

2015 ◽  
Vol 73 (6) ◽  
pp. 1378-1386 ◽  
Author(s):  
Fatemeh Hashemzadeh
Keyword(s):  
Wide Band ◽  
Xrd Analysis ◽  
Structural Features ◽  
Ammonium Ion ◽  
Layered Perovskite ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
Quantum Size ◽  
Calcium Niobate ◽  
Molecular Aspects

The single phase layered perovskite-type niobate KCa2Nb3O10 was obtained by a solid state reaction of the starting materials (K2CO3, CaCO3 and Nb2O5) at 1,200 °C. Then the H+-exchanged form (HCa2Nb3O10) was successfully exfoliated into colloidal porous single layers on the intercalating action of tetra(butyl)ammonium ion. The various characterization techniques such as X-ray diffraction (XRD), field-emission scanning electron microscopy, N2 absorption–desorption and diffuse reflectance UV–visible spectrometry gave important information on the unusual structural features of the perovskite-related niobate nanosheets. XRD analysis of the exfoliated nanosheets showed a unique profile with wide peaks that represented individual molecular aspects of the nanosheets. The Brunauer–Emmett–Teller isotherm of the exfoliated coiled nanosheets showed a sharp increase in the surface area by a factor of >30 in comparison to parent layered material, which is due to the exfoliation and restacking process. The nanosheets in this study were also found to act as a semiconductor with a wide band gap that is due to the quantum size effect.

Epitaxial Growth of Aluminum Nitride on Sapphire and Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
K. Dovidenko ◽  
S. Oktyabrsky ◽  
J. Narayan ◽  
M. Razeghi
Keyword(s):  
Epitaxial Growth ◽  
Substrate Surface ◽  
Wide Band ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
High Quality ◽  
Microstructural Characteristics ◽  
X Ray ◽  
Si Substrates ◽  
Transmission Electron

ABSTRACTThe microstructural characteristics of wide band gap semiconductor, hexagonal A1N thin films on Si(100), (111), and sapphire (0001) and (10ī2) were studied by transmission electron microscopy (TEM) and x-ray diffraction. The films were grown by MOCVD from TMA1 + NH3 + N2 gas mixtures. Different degrees of film crystallinity were observed for films grown on α-A12O3 and Si substrates in different orientations. The epitaxial growth of high quality single crystalline A1N film on (0001) α-Al2O3 was demonstrated with a dislocation density of about 2*10 10cm−2 . The films on Si(111) and Si(100) substrates were textured with the c-axis of A1N being perpendicular to the substrate surface.

Stress origin and relaxation in epitaxial AlN thin films on SiC

2001 ◽  
Vol 696 ◽  
Author(s):  
Ravi Bathe ◽  
R.D. Vispute ◽  
Daniel Habersat ◽  
R. P. Sharma ◽  
T. Venkatesan ◽  
...  
Keyword(s):  
Thin Films ◽  
Rutherford Backscattering Spectrometry ◽  
Wide Band ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
X Ray ◽  
Force Microscopy ◽  
Ion Channeling ◽  
Atomic Force ◽  
Highly Strained

AbstractWe have investigated the epitaxy, surfaces, interfaces, and defects in AlN thin films grown on SiC by pulsed laser deposition. The stress origin, evolution, and relaxation in these films is reported. The crystalline structure and surface morphology of the epitaxially grown AlN thin films on SiC (0001) substrates have been studied using x-ray diffraction (θ–2θ, ω, and Ψ scans) and atomic force microscopy, respectively. The defect analysis has been carried out by using Rutherford backscattering spectrometry and ion channeling technique. The films were grown at various substrate temperatures ranging from room temperature to 1100 °C. X-ray diffraction measurements show highly oriented AlN films when grown at temperatures of 750- 800 °C, and single crystals above 800 °C. The films grown in the temperature range of 950 °C to 1000 °C have been found to be highly strained, whereas the films grown above 1000 °C were found to be cracked along the crystallographic axes. The results of stress as a function of growth temperature, thermal mismatch, growth mode, and buffer layer thickness will be presented, and the implications of these results for wide band gap power electronics will be discussed.

Studies on the Preparation and Properties of Sheet Ni-Doped ZnO

2011 ◽  
Vol 356-360 ◽  
pp. 435-438
Author(s):  
Ling Cao ◽  
Dai Zong An ◽  
Yan Xin Wang ◽  
Shan Shan He ◽  
Chuang Ju Dong
Keyword(s):  
Growth Parameters ◽  
Wide Band ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
Manipulation System ◽  
Doped Zno ◽  
Zno Crystal ◽  
Analysis System

ZnO is a direct wide band-gap Ⅱ-Ⅵ semiconductor material. For decades, ZnO has gained more and more attention as a wide band semiconductor. This paper introduced a modified homogeneous precipitation method to prepare sheet Ni-doped ZnO crystal. The preparation process was studied and the mechanism of this method was discussed. The properties of the sheet Ni-doped ZnO crystal and the effects of growth parameters on the quality of sheet Ni-doped ZnO crystal were studied using XTJ30-micro image manipulation system, thermal analysis system, X-ray diffraction. etc.

Electron Diffusion in ZnO Nanomaterial: An Ac Impedance Investigation

2011 ◽  
Vol 312-315 ◽  
pp. 393-398
Author(s):  
Roshidah Rusdi ◽  
Norlida Kamarulzaman ◽  
Mohamed Nor Sabirin ◽  
Zurina Osman ◽  
Azilah Abd Rahman
Keyword(s):  
Sol Gel ◽  
Wide Band ◽  
Ac Impedance ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
Electron Diffusion ◽  
Electron Conduction ◽  
Diffusion Characteristics ◽  
Zno Nanomaterials ◽  
Electrical Components

ZnO is a wide band gap semiconductor with many applications such as in solar cells, varistors, and other electrical components. The ZnO material was synthesized using a sol-gel method. The material was characterized using X-Ray diffraction (XRD) and scanning electron microscopy (SEM). The material is pure and single phase. Electron conduction in ZnO nanomaterials was done using alternating current (ac) impedance. The frequency ranges of the measurements used were 1x 10-3 Hz to 1x 106 Hz and the ac impedance measurements were done within a temperature range of 60oC to 100oC. Nyquist plots were drawn and bulk resistances were obtained. Subsequently, conductivity values were calculated and the diffusion characteristics were obtained. From further analysis of the conductivities with temperature, the diffusion of electrons in the material was studied. It was found that the conductivity increased with the increase of temperature which meant that the rate of diffusion of the electrons through the materials also increased. An Arrhenius relation was concluded for the electron diffusion in the ZnO nanomaterials.

Nanostructure Assembly of Indium Sulphide Quantum Dots and Their Characterization

2008 ◽  
Vol 8 (2) ◽  
pp. 689-694 ◽  
Author(s):  
B. Vigneashwari ◽  
V. Ravichandran ◽  
P. Parameswaran ◽  
S. Dash ◽  
A. K. Tyagi
Keyword(s):  
Quantum Dots ◽  
Colloidal Suspension ◽  
Wide Band ◽  
X Ray Diffraction ◽  
Hydrothermal Route ◽  
Wide Band Gap ◽  
X Ray ◽  
Glass Substrates ◽  
Series Of Experiments ◽  
Indium Sulphide

Nanocrystals (∼5 nm) of the semiconducting wide band gap material β-In2S3 obtained by chemical synthesis through a hydrothermal route were characterized for phase and compositional purity. These nanoparticles exhibited quantum confinement characteristics as revealed by a blue-shifted optical absorption. These quantum dots of β-In2S3 were electrically driven from a monodisperse colloidal suspension on to conducting glass substrates by Electophoretic Deposition (EPD) technique and nanostructural thin films were obtained. The crystalline and morphological structures of these deposits were investigated by X-ray diffraction and nanoscopic techniques. We report here that certain interesting nanostructural morphologies were observed in the two-dimensional quantum dot assemblies of β-In2S3. The effect of the controlling parameters on the cluster growth and deposit integrity was also systematically studied through a series of experiments and the results are reported here.

scholarly journals Synthesis of lead-based 1212 and 3212 superconductors by an aqueous sol-gel method

2009 ◽  
Vol 7 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Giedre Nenartaviciene ◽  
Ramunas Skaudzius ◽  
Rimantas Raudonis ◽  
Aivaras Kareiva
Keyword(s):  
Sol Gel ◽  
Xrd Analysis ◽  
Structural Features ◽  
Complexing Agents ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resistivity Measurements ◽  
Ceramic Samples ◽  
Xrd Patterns ◽  
Sol Gel Synthesis

AbstractThe aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr2(Y,Ca)Cu2O7±x (Pb-1212) and (Pb2,Cu)Sr2(Y,Ca)Cu2O8±x (Pb-3212) superconductors using two different complexing agents, namely 1,2-ethanediol and tartaric acid was studied. The phase transformations, composition and micro-structural features in the polycrystalline samples were studied by powder X-ray diffraction analysis (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XRD analysis of the ceramic samples obtained by calcination of Pb-Sr-Y-Ca-Cu-O acetate-glycolate precursor gels in air, for 10 hours at 800°C and at 825°C, showed the presence of homogeneous Pb-1212 and Pb-3212 crystallites as major phases. The XRD patterns of the ceramics obtained from Pb-Sr-Y-Ca-Cu-O acetate-tartrate precursor gels, however, showed multiphasic character. The critical temperature of superconductivity (TC (onset)) observed by resistivity measurements were found to be 91 K and 75 K for Pb-1212 and Pb-3212 samples, respectively.

Synthesis and Characterization of Al4SiC4: A “New” Wide Band Gap Semiconductor Material

2015 ◽  
Vol 821-823 ◽  
pp. 974-977 ◽  
Author(s):  
Dimitrios Zevgitis ◽  
Odette Chaix-Pluchery ◽  
Beatrice Doisneau ◽  
Mircea Modreanu ◽  
Joseph La Manna ◽  
...  
Keyword(s):  
Nir Spectroscopy ◽  
Wide Band ◽  
Graphite Crucible ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
Transmission Electron ◽  
Temperature Solution ◽  
Microscopy Techniques

High temperature solution growth of Al4SiC4 single crystals was carried out from the melt of silicon and aluminium pieces in a graphite crucible used as carbon source (typically 1800°C under 1 bar of argon). The obtained crystals, in the mm scale, were then characterized by a variety of techniques including: Raman spectroscopy, transmission electron microscopy techniques, X-ray diffraction and UV-Vis-NIR spectroscopy. A good structural quality was revealed by TEM, ensuring a well resolved Raman spectrum. The UV-Vis transmission spectrum shows an optical gap located around 2-2.5 eV.

Effects of Doping Ratio of Cobalt and Iron on the Structure and Optical Properties of Bi3.25La0.75FexCo1–xTi2O12 (x = 0, 0.25, 0.5, 0.75, 1)

2015 ◽  
Vol 15 (10) ◽  
pp. 7841-7844 ◽  
Author(s):  
Myoung Geun Song ◽  
Jun Young Han ◽  
Chung Wung Bark
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Complex Oxides ◽  
Wide Band ◽  
Iron Doping ◽  
Cobalt Doping ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
Visible Absorption ◽  
Doping Ratio

The wide band gap of complex oxides is one of the major obstacles limiting their use in photovoltaic cells. To identify an effective route for tailoring the band gap of complex oxides, this study examined the effects of cobalt and iron doping on lanthanum-modified Bi4Ti3O12-based oxides synthesized using a solid reaction. The structural and optical properties were analyzed by X-ray diffraction and ultraviolet-visible absorption spectroscopy. As a result, the optimal iron to cobalt doping ratio in bismuth titanate powder resulted in an ∼1.8 eV decrease in the optical band gap. This new route to reduce the optical bandgap can be adapted to the synthesis of other complex oxides.

Growth and Characterization of ZnO Nanonail

2004 ◽  
Vol 829 ◽  
Author(s):  
H. W. Seo ◽  
D. Wang ◽  
Y. Tzeng ◽  
N. Sathitsuksanoh ◽  
C. C. Tin ◽  
...  
Keyword(s):  
Vapor Deposition ◽  
Chemical Vapor ◽  
Wide Band ◽  
Processing Parameters ◽  
Photoluminescence Spectroscopy ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
X Ray ◽  
Thermal Chemical Vapor Deposition

ABSTRACTZinc oxide (ZnO) is an interesting material for short-wavelength optoelectronics due to its wide band gap. The nanostructures of ZnO are also intriguing since a variety of morphology can be obtained by employing different processing parameters. In our laboratory, ZnO nanonails were successfully synthesized at low temperature using a thermal chemical vapor deposition. The morphology of the sample was studied by using scanning electron microscopy. The shape of the nail head can be controlled from hexagon to quasi-circular shape. X-ray diffraction, Raman scattering, photoluminescence spectroscopy were also performed to analyze the ZnO nanonail. Photoluminescence spectroscopy suggested that the defects in the ZnO nanonail and nanobone are of different nature.

MBE Growth and Properties of Wide Band-Gap II-VI Strained-Layer Superlattice

1992 ◽  
Vol 242 ◽  
Author(s):  
Hailong Wang ◽  
Jie Cui ◽  
Aidong Shen ◽  
Liang Xu ◽  
Yunliang Chen ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Wide Band ◽  
Far Infrared ◽  
Atomic Layer ◽  
X Ray Diffraction ◽  
Wide Band Gap ◽  
Strained Layer ◽  
Pl Spectra ◽  
Reflectivity Spectra ◽  
Strained Layer Superlattice

ABSTRACTThe (ZnSe) /(ZnS ), strained layer super-lattices (SLSs) on (100) GaAs and (ZnTe)/(ZnSe) SLSs on (100) InP have been grown by molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE). The structural characteristics of these SLSs were investigated in situ RHEED observation, low-angle X-ray diffraction spectra, TED image and AES analysis. The optical properties of the SLSs, such as refractive index of superlattice materials, photoluminescence (PL) spectra, transient PL spectra, Raman spectra, far-infrared reflectivity spectra and Optical nonlinear have been studied.

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