scholarly journals Hetero CuOx/ZnO micro-/nanostructure: Carbothermal reduction–vapour phase transport

2018 ◽  
Vol 57 (4) ◽  
Author(s):  
Ali Rahmati ◽  
F. Rahimi Bayaz ◽  
A. Lotfiani ◽  
M. Kouhestani
Keyword(s):  
Carbothermal Reduction ◽  
Chemical Vapour ◽  
Green Emission ◽  
Catalyst Layer ◽  
Hexagonal Wurtzite Structure ◽  
Vapour Phase ◽  
Uv Emission ◽  
Cu Catalyst ◽  
Vapour Phase Transport

ZnO micro-/nanostructures were synthesized by the carbothermal reduction–chemical vapour transport method. This work is focused on the effect of the substrate temperature and Cu catalyst layer on the shape and geometry of ZnO micro-/nanostructures. The thermally oxidized Cu template affects the structure, chemical identity, optical and photoluminescence properties of the ZnO micro-/nanostructure and results in a CuOx/ZnO heterostructure. SEM studies give a direct evidence of the role of deposition temperature and Cu catalyst in the formation of a stable hemisphere based wire, a comb-like cantilever, a javelin-like tetrapod, a spherical and polyhedral cage of ZnO. XRD and Raman measurements confirm a hexagonal wurtzite structure of the ZnO micro-/nanostructure. The absorption edge of the ZnO/CuOx heterostructure is redshifted in comparison to the pure ZnO structure. PL studies indicate that the UV emission can be suppressed significantly while the green emission is enhanced due to the change in the morphology of ZnO micro-/nanostructures.

Notizen: The Crystal Structure of MnIn2Se4, a Ternary Layered Semiconductor

1991 ◽  
Vol 46 (8) ◽  
pp. 1122-1124 ◽  
Author(s):  
K.-J. Range ◽  
U. Klement ◽  
G. Döll ◽  
E. Bucher ◽  
J. R. Baumann
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
Layered Structure ◽  
Chemical Vapour ◽  
Vapour Phase ◽  
Tetrahedral Coordination ◽  
Layered Semiconductor ◽  
Vapour Phase Transport ◽  
Phase Transport ◽  
Transport Technique

Single crystals of MnIn2Se4 have been grown by the chemical vapour phase transport technique using AlCl3 as the transporting agent. The structure was refined to R = 0.064, Rw, = 0.059 for 609 reflections. MnIn2Se4 (R 3̄m, hexagonal axes a = 4.051(1), c = 39.464(2) Å, c/a = 9.74, Z = 3) crystallizes with a nearly close-packed layered structure (sequence of the Se layers ABCA|CABC|BCAB) with Moct (= 0.56 Mn + 0.44 In) in octahedral coordination (Moct,–Se = 6 × 2.721(1) A) and Mtet (= 0.78 In + 0.22 Mn) in tetrahedral coordination (Mtet-Se = 1 × 2.527(2) and 3 × 2.593(1) Å). The overall layer sequences is ΑβΒαCyA| Cα AγBβC| BγCβAα B.

Fabrication and Characterizations of ZnO and ZnO:Mn Nanocrystalline Thin Films

2003 ◽  
Vol 764 ◽  
Author(s):  
Yichun Liu ◽  
Dongxu Zhao ◽  
X.T. Zhang ◽  
Dezhen Shen ◽  
D.O. Henderson ◽  
...  
Keyword(s):  
Thin Films ◽  
Green Emission ◽  
Hexagonal Wurtzite Structure ◽  
Ultraviolet Emission ◽  
Mn Doping ◽  
Surface And Interface ◽  
Hole Trapping ◽  
Uv Emission ◽  
Zno Nanocrystals ◽  
Nanocrystalline Thin Films

AbstractThis paper provides a brief summary of the structural and optical study of ZnO and ZnO:Mn materials fabricated from simple process: oxidation of ZnS and ZnS:Mn thin films grown by LPMOCVD. Both structural analysis and optical characterization have confirmed the good quality ZnO material formation. XRD results suggest that the fabricated ZnO film is composed of ∼30 nm ZnO nanocrystals with a hexagonal wurtzite structure. Raman spectra show a strong resonant multiphonon effect. In all cases, a UV emission is observed at ∼ 380 nm. A green emission is also observed in the ZnO nanocrystalline film. On the other hand, it is demonstrated that the Mn doping in ZnS film can dramatically affect the luminescence properties of end products: nanocrystalline ZnO thin films. The photoluminescence spectra of the films with an optimized Mn doping concentration only showed the ultraviolet emission, while the green emission was fully quenched. It is argued that the presence of the Mn can effectively passivate the electron and hole trapping sites at the surface and interface of the ZnO nanocrystals.

The Role of Oxygen Ambience on the Optical Characteristics of ZnO Films

2013 ◽  
Vol 711 ◽  
pp. 26-31
Author(s):  
Feng Li ◽  
Ru Yuan Ma
Keyword(s):  
Grain Size ◽  
Oxygen Vacancies ◽  
Green Emission ◽  
Intensity Change ◽  
Zno Films ◽  
Radio Frequency Magnetron Sputtering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Uv Emission

Zinc oxide (ZnO) films are grown by two methods-pulse laser deposition (PLD) and radio-frequency magnetron sputtering at various oxygen ambiences. Based on x-ray diffraction spectra and photoluminescence (PL) spectra, effects of the oxygen ambient on the grain size and emission properties of the ZnO films are investigated. For the samples grown by PLD, the PL spectrum consists of a single ultraviolet (UV) peak except one sample deposited at a low O2 pressure of 7 Pa. All the samples grown by sputtering have both a UV peak and a green emission. The disappearance of the green emission of the PLD samples is ascribed to deficiency of oxygen vacancies (Ov), and the green emission of the sample grown by sputtering is due to abundant Ov. The intensity change of the UV emission is due to the variation of exciton emission, which is related to grain size and stoichiometry. The position shifting of the UV peak of the PLD samples originates from the Zn interstitial-related degradation of stoichiometry.

Darstellung und Kristallstruktur von NdSe1,9/ Preparation and Crystal Structure of NdSe1,9

1989 ◽  
Vol 44 (3) ◽  
pp. 261-264 ◽  
Author(s):  
W. Urland ◽  
P. Plambeck-Fischer ◽  
M. Grupe
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Chemical Vapour ◽  
Vapour Phase ◽  
Defect Layer ◽  
Space Group ◽  
Vapour Phase Transport ◽  
Phase Transport ◽  
Subsequent Chemical

Abstract NdSe1,9 has been prepared as grey, strongly reflecting platelets by reaction of elemental neodymium with selenium in the ratio 1 :2 and subsequent chemical vapour phase transport with iodine. It crystallizes in the tetragonal space group P42/n with a = 925.36(7), c = 1679.2(3) pm and Z = 20. The structure determination results in a formulation of NdSe1,9 as Nd 20(Se(I)2)8Se(I)2⃞2Se(II)20, where the defect layer built from the Se(I)22- and Se(I)2- ions corresponds to the F layer in the PbFCl substructure.

scholarly journals The structure of Zn1 xMnxIn2Se4crystals grown by chemical vapour phase transport

2004 ◽  
Vol 16 (21) ◽  
pp. 3555-3562 ◽  
Author(s):  
J Mantilla ◽  
G E S Brito ◽  
E ter Haar ◽  
V Sagredo ◽  
V Bindilatti
Keyword(s):  
Chemical Vapour ◽  
Vapour Phase ◽  
Vapour Phase Transport ◽  
Phase Transport

Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation

1991 ◽  
Vol 56 (10) ◽  
pp. 1993-2008
Author(s):  
S. Hanafi ◽  
G. M. S. El-Shafei ◽  
B. Abd El-Hamid
Keyword(s):  
Particle Size ◽  
Vapour Phase ◽  
Tricalcium Silicate ◽  
Active Centers ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Intermediate Size ◽  
Surface Active ◽  
Temperature Activation

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.

scholarly journals Role of dislocations in nitride laser diodes with different indium content

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Agata Bojarska-Cieślińska ◽  
Łucja Marona ◽  
Julita Smalc-Koziorowska ◽  
Szymon Grzanka ◽  
Jan Weyher ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Defect Density ◽  
Laser Diodes ◽  
Diffusion Path ◽  
Vapour Phase ◽  
Indium Content ◽  
Nonradiative Recombination ◽  
Light Emitters ◽  
Vapour Phase Epitaxy

AbstractIn this work we investigate the role of threading dislocations in nitride light emitters with different indium composition. We compare the properties of laser diodes grown on the low defect density GaN substrate with their counterparts grown on sapphire substrate in the same epitaxial process. All structures were produced by metalorganic vapour phase epitaxy and emit light in the range 383–477 nm. We observe that intensity of electroluminescence is strong in the whole spectral region for devices grown on GaN, but decreases rapidly for the devices on sapphire and emitting at wavelength shorter than 420 nm. We interpret this behaviour in terms of increasing importance of dislocation related nonradiative recombination for low indium content structures. Our studies show that edge dislocations are the main source of nonradiative recombination. We observe that long wavelength emitting structures are characterized by higher average light intensity in cathodoluminescence and better thermal stability. These findings indicate that diffusion path of carriers in these samples is shorter, limiting the amount of carriers reaching nonradiative recombination centers. According to TEM images only mixed dislocations open into the V-pits, usually above the multi quantum wells thus not influencing directly the emission.

ORGANIC CuPc COATING INDUCED IMPROVED PHOTOLUMINESCENCE AND PHOTOCONDUCTIVITY OF ZnO NANOWIRES ARRAY

2012 ◽  
Vol 05 (03) ◽  
pp. 1250021 ◽  
Author(s):  
SOUMEN DHARA ◽  
P. K. GIRI
Keyword(s):  
Charge Transfer ◽  
Dark Current ◽  
Surface Defects ◽  
Green Emission ◽  
Charge Transfer Process ◽  
Current Ratio ◽  
Uv Emission ◽  
Surface Covering ◽  
Interfacial Charge ◽  
Nanowires Array

In this work, we investigated the effect of organic CuPc coating on the surface of the ZnO NWs for possible improvement in the photoluminescence, photoconductivity and photoresponse. As a result of surface covering, the UV emission is enhanced by a factor of 7–8 while the green emission is reduced to half. Despite an increase in dark current after the CuPc covering, we obtained a significant improvement in the photocurrent and photoresponse rate. The photocurrent-to-dark current ratio is nearly doubled and the photoresponse process becomes faster for the ZnO/CuPc heterostructure. Improvements in the photoluminescence and photoconductivity for the ZnO/CuPc heterostructure are explained on the basis of modification of surface defects and interfacial charge transfer process.

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