Correlation Between Microstructure and Optical Properties of ZnO Based Nanostructures Grown by MOCVD

2008 ◽  
Vol 1074 ◽  
Author(s):  
Farid Falyouni ◽  
Julien Barjon ◽  
Vincent Sallet ◽  
Alain Lusson ◽  
Guy Garry ◽  
...  
Keyword(s):  
Low Temperature ◽  
Structural Properties ◽  
Quantum Confinement ◽  
Dopant Concentration ◽  
Quantum Confinement Effect ◽  
Chemical Vapor ◽  
Blue Shift ◽  
Transmission Electron ◽  
Optical Signature ◽  
Excitonic Emission

ABSTRACTThe correlation between structural properties of ZnO sharp conical needles grown by Metallorganic Chemical Vapor Deposition (MOCVD) on sapphire substrate and their optical signature measured by low temperature cathodoluminescence (CL) is investigated. Transmission Electron Microscopy (TEM) shows the excellent structural properties of these needles from their base up to the end of the tip. In order to probe the emission of the needles along their length, UV CL mapping has been performed at low temperature on a single needle previously characterized by TEM. A clear blue shift of 25meV is observed for the excitonic emission close to the needle tip. This shift is too high to be fully attributed to quantum confinement. Although, it qualitatively agrees with previous observations which assigned it to a surface contribution becoming dominant upon size shrinking, the effect is less pronounced. The results are discussed in term of surface quality and other possible contributions associated to a decrease of the n-dopant concentration and to quantum confinement effect close to the tip.

Low-Temperature Synthesis of Nearly Monodisperse ZnS Nanospheres Using a Facile Solution-Phase Approach

2006 ◽  
Vol 59 (11) ◽  
pp. 791 ◽  
Author(s):  
Weizhi Wang ◽  
Liyong Chen ◽  
Shutao Wang ◽  
Baojuan Xi ◽  
Shenglin Xiong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Confinement ◽  
Quantum Confinement Effect ◽  
Reaction Times ◽  
Blue Shift ◽  
Average Diameter ◽  
Solution Phase ◽  
Sulfur Source ◽  
Low Temperature Synthesis ◽  
Ft Ir

This paper describes a facile and controllable solution-phase process for the preparation of nearly monodisperse ZnS nanospheres, with an average diameter of 150 nm, at a low temperature (80°C). Thiourea is used both as a sulfur source and as a capping ligand which can direct initially formed ZnS particles to aggregate into nanospheres. The average diameter of ZnS nanospheres could be readily controlled by varying the reaction time. On the basis of the results of different reaction times and Fourier transform infrared (FT-IR) spectrum analysis, a possible aggregation mechanism to form ZnS nanospheres is proposed. The UV-vis absorption spectra of the obtained ZnS nanospheres exhibits an obvious blue shift due to the quantum confinement effect.

CdS/Cyclohexylamine Inorganic–Organic Hybrid Semiconductor Nanofibers with Strong Quantum Confinement Effect

2008 ◽  
Vol 8 (8) ◽  
pp. 3914-3920 ◽  
Author(s):  
Libo Fan ◽  
Hongwei Song ◽  
Haifeng Zhao ◽  
Guohui Pan ◽  
Lina Liu ◽  
...  
Keyword(s):  
Quantum Confinement ◽  
Quantum Confinement Effect ◽  
Blue Shift ◽  
Average Diameter ◽  
Confinement Effect ◽  
Dimethyl Formamide ◽  
Organic Hybrid ◽  
Cds Nanorods ◽  
Transmission Electron ◽  
20 Nm

Inorganic–organic hybrid semiconductor nanofibers of CdS/CHA (CHA = cyclohexylamine) were successfully synthesized by a simple solvothermal method. The fibers obtained had average diameter of 20 nm and length of several micrometers. In these fibers, periodic layer-like sub-nanometer structures with thickness of ∼3 nm were identified by high-resolution transmission electron microscope (HR-TEM). The absorption of the hybrids exhibited a large blue-shift in contrast to the bulk, which was attributed to strong quantum confinement effect (QCE) induced by internal sub-nanometer structures. Pure hexagonal wurtzite CdS (H-CdS) nanorods were also obtained by extracting the CdS/CHA hybrids with dimethyl formamide (DMF). The rods obtained had average diameter of 20 nm and length of 200 nm. A CdS/CHA/polyvinyl alcohol (PVA) composite film emitting white light was prepared by spin coating.

Opto-Electronic Properties of Green Synthesized ZnS Nanostructures

2018 ◽  
Vol 17 (04) ◽  
pp. 1760032
Author(s):  
Sujata Deb ◽  
P. K. Kalita ◽  
P. Datta
Keyword(s):  
Quantum Confinement ◽  
Quantum Confinement Effect ◽  
Blue Shift ◽  
Cubic Phase ◽  
Capping Agent ◽  
X Ray Diffraction ◽  
Chemical Route ◽  
Transmission Electron ◽  
Wet Chemical ◽  
Green Capping Agent

ZnS nanostructures are synthesized by a wet chemical route using starch as green capping agent under nitrogen environment. The as-prepared nanostructures are characterized structurally, optically and electrically. X-ray diffraction (XRD) spectra confirm that the zinc sulfide (ZnS) nanoparticles have cubic phase (zinc blende). UV–Vis spectrum of the sample clearly shows that the absorption peak exhibits blue shift compared to their bulk counterpart, which confirms the quantum confinement effect of the nanostructures. Its photoluminescence (PL) spectrum shows near band gap emission at 392[Formula: see text]nm and extrinsic emission at 467[Formula: see text]nm. The particle sizes calculated from XRD and UV studies are in fair agreement with high resolution transmission electron microscopy (HRTEM) results. Starch is found to be a noble capping agent in bringing quantum confinement. The synthesis under nitrogen environment has been observed to produce quality products by reducing the oxide traces. Moreover, the I–V characteristics under dark and illumination show that ZnS can be more suitable as photodetector.

Synthesis and Characterization of Mn2+ Doped ZnS Using Reverse Miceller Method

2014 ◽  
Vol 970 ◽  
pp. 283-287
Author(s):  
Rahizana Mohd Ibrahim ◽  
Markom Masturah ◽  
Huda Abdullah
Keyword(s):  
Quantum Confinement ◽  
Quantum Confinement Effect ◽  
Blue Shift ◽  
Band Gap Energy ◽  
Confinement Effect ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Vis Spectroscopy ◽  
Size Of Particles ◽  
Absorbance Spectra

In this work we synthesized the monodisperse of Zn1-xMnxS with x =0.00,0.02,0.04,0.06,0.08 and 0.10 nanoparticles by reverse micelle method using sodium bis (2-ethylhexyl) sulfosuccinate (AOT) as surfactant. The prepared particles were characterized using UV-Visible Spectroscopy, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Photoluminescence (PL) for size, morphology and optical of the samples .UV-vis absorbance spectra for all of the synthesized nanoparticles show the maximum absorption for all samples is observed at range 210 - 300 nm . The absorption edge shifted to lower wavelengths when doping with ion Mn as per UV-Vis spectroscopy. The band gap energy values were increase from 4.50eV to 4.90 eV. This blue shift is attributed to the quantum confinement effect. The size of particles is found to be 3-5nm range. The Mn2+ doped ZnS nanoparticles using reverse micelles method shows the enhance of PL intensity results in monodisperse nanoparticles. Keywords: Nanoparticles; UV-vis absorbance spectra; quantum confinement effect; photoluminescence.

Fabrication and Optical Properties of ZnO Quantum Dots

2007 ◽  
Vol 31 ◽  
pp. 71-73
Author(s):  
X.H. Zhang ◽  
Soo Jin Chua ◽  
A.M. Yong ◽  
S.Y. Chow ◽  
H.Y. Yang ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Confinement ◽  
Silicon Oxide ◽  
Quantum Confinement Effect ◽  
Blue Shift ◽  
Si Substrates ◽  
Transmission Electron ◽  
Oxide Matrix ◽  
Zno Quantum Dots ◽  
Subsequent Thermal Annealing

Using a simple process of the deposition of ZnO thin films on SiOx/Si substrates and subsequent thermal annealing, we fabricated ZnO quantum dots embedded in silicon oxide matrix. The ZnO quantum dots were characterized using transmission electron microscopy and timeintegrated photoluminescence. The photoluminescence of the quantum dots show a blue-shift of 47 meV due to the quantum confinement effect.

Formation of Luminescent Si Nanocrystals by High-Temperature Annealing of Ion-Beam-Sputtered Si/SiO2 Multilayers

2003 ◽  
Vol 775 ◽  
Author(s):  
Suk-Ho Choi ◽  
Jun Sung Bae ◽  
Kyung Jung Kim ◽  
Dae Won Moon
Keyword(s):  
Quantum Confinement ◽  
Radiative Recombination ◽  
Ion Beam ◽  
Quantum Confinement Effect ◽  
Visible Range ◽  
Ion Beam Sputtering ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Beam Sputtering ◽  
Microscopy Images

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.

Low Temperature Large Scale CVD Synthesis of Nano Onion-Like Fullerenes

2012 ◽  
Vol 490-495 ◽  
pp. 3211-3214 ◽  
Author(s):  
Lei Shan Chen ◽  
Cun Jing Wang
Keyword(s):  
Electron Microscopy ◽  
Low Temperature ◽  
Aluminum Hydroxide ◽  
Large Scale ◽  
Iron Catalyst ◽  
Chemical Vapor ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Naoh Solution ◽  
Synthesis Reactions

Synthesis reactions were carried out by chemical vapor deposition using iron catalyst supported on aluminum hydroxide at 400 °C and 420 °C, in the presence of argon as carrier gas and acetylene as carbon source. The aluminum hydroxide support was separated by refluxing the samples in 40% NaOH solution for 2 h and 36% HCl solution for 24 h, respectively. The samples were characterized by field-emission scanning electron microscopy, energy dispersive spectroscopy, high-resolution transmission electron microscopy and X-ray diffraction. The results show that carbon nanotubes were the main products at 420 °C, while large scale high purity nano onion-like fullerenes encapsulating Fe3C, with almost uniform sizes ranging from 10-50 nm, were obtained at the low temperature of 400 °C.

Blue Shifting of Hydrogenated Silicon Carbide Multiple Quantum Wells

2011 ◽  
Vol 480-481 ◽  
pp. 629-633
Author(s):  
Wen Teng Chang ◽  
Yu Ting Chen ◽  
Chung Chin Kuo
Keyword(s):  
Silicon Carbide ◽  
Quantum Wells ◽  
Quantum Confinement Effect ◽  
Chemical Vapor ◽  
Blue Shift ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Plasma Chemical ◽  
Hydrogenated Silicon ◽  
Plasma Chemical Vapor Deposition

Five-period hydrogenated silicon carbide (SiC) multiple quantum wells with silicon dioxide (SiO2) or silicon nitride (SiN) dielectric that were synthesized by high density plasma chemical vapor deposition were studied using photoluminescence (PL) spectroscopy to understand its blue shift. Rapid thermal annealing induced significant blue shifting in the PL spectra after fluorine ion implantation due to crystallization. The thinning of the SiC causes blue shift due to the quantum confinement effect. The higher PL intensity of the amorphous SiC:H in SiO2 than in SiC/SiN may be attributed to the high number of non-radiative sites on its surface. Annealing with nitrogen may cause impurities in SiC/SiO2, thereby broadening the PL peak.

QUANTUM CONFINEMENT EFFECT IN HgTe NANOCRYSTALS AND VISIBLE LUMINESCENCE

2004 ◽  
Vol 03 (03) ◽  
pp. 393-401 ◽  
Author(s):  
S. RATH ◽  
A. K. DASH ◽  
S. N. SAHU ◽  
S. NOZAKI
Keyword(s):  
Valence Band ◽  
Quantum Confinement ◽  
Quantum Confinement Effect ◽  
Free Exciton ◽  
Confinement Effect ◽  
Electrochemical Technique ◽  
Cubic Phase ◽  
Exciton Transition ◽  
Mercury Telluride ◽  
Transmission Electron

Mercury Telluride ( HgTe ) nanocrystals with a mean size of 5.35 nm have been synthesized by an electrochemical technique. Structural analysis by transmission electron microscopy and glancing angle X-ray diffraction studies indicate the presence of cubic phase HgTe nanocrystals in the deposit. Optical absorption measurements reveal two well resolved excitonic peaks around 578.5 nm and 550 nm attributed to heavy hole valence band (HVB)–conduction band (CB) and light hole valence band (LVB)–CB transitions, respectively, and suggest a band opening of bulk inverted narrow band gap HgTe as a result of strong quantum confinement effect (QCE). Visible photoluminescence (PL) of HgTe nanocrystals indicates free exciton transition around 579.5 nm as observed from the PL measurement at 300 K along with a bound exciton dominated band around 588 nm. Micro-Raman measurements at 300 K indicate the 1LO vibrational mode at 142.6 cm-1 shifted by 6 cm-1 from its standard bulk value and confirm the QCE.

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