Transmittance, Absorbance and Emission of Ga related Defects in Ga-doped ZnO Nanocrystal Films

MRS Advances ◽  
2020 ◽  
Vol 5 (59-60) ◽  
pp. 3015-3022
Author(s):  
Tetyana V. Torchynska ◽  
Brahim El Filali ◽  
Jose L. Casas Espinola ◽  
Chetzyl I. Ballardo Rodriguez ◽  
Georgiy Polupan ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Emission Band ◽  
Free Exciton ◽  
Thermal Quenching ◽  
Ultrasonic Spray Pyrolysis ◽  
Optical Transmittance ◽  
Optical Bandgap ◽  
Zno Films ◽  
Near Band Edge ◽  
Phonon Replica

ZnO films grown by ultrasonic spray pyrolysis with different Ga contents in the range of 1.0-6.5 at% on quartz substrates have been studied. The ZnO:Ga films were annealed at 400°C for 4h in a nitrogen flow. Morphology, emission, transmittance, absorbance and electrical resistivity were controlled. It is revealed that with a small content of Ga ≤ 4.0 at%, the ZnO:Ga films maintain a flat morphology, their transmittance increases to 86% together with the increase of the ZnO optical bandgap to 3.28 eV and the intensity enlargement of the near band edge (NBE) emission band A (3.188 eV). Furthermore, the new NBE emission band B (3.072 eV) appears in photoluminescence (PL) spectra at Ga contents ≥ 1.5 at%. Simultaneously, the process of decreasing electrical resistivity becomes saturating. The last effect is attributed to the self-compensation effect in n-type ZnO:Ga films related to the generation of acceptor type complexes (VZn2- - GaZn+). The thermal quenching of the PL intensities of the A and B PL bands is studded at 18-290K, which allows assigning the PL band A to the LO-phonon replica of the free exciton emission and the band B to the emission in donor-acceptor pairs: shallow donors - acceptor complexes (VZn2- - GaZn+). The NBE emission intensity drops and the ZnO optical bandgap demonstrates the shift to a lower energy at Ga doping up to ≤ 6.5 at%. Optimal Ga concentrations have been estimated to produce ZnO:Ga films with flat morphology, high optical transmittance and bright NBE emission.

Emission Diversity of ZnO Nanocrystals with Different Growth Temperatures

2014 ◽  
Vol 1675 ◽  
pp. 45-51
Author(s):  
E. Velázquez Lozada ◽  
T. Torchynska ◽  
G. Camacho González
Keyword(s):  
Free Exciton ◽  
Ultrasonic Spray Pyrolysis ◽  
Second Order ◽  
Zno Films ◽  
Near Band Edge ◽  
Phonon Replica ◽  
Ultrasonic Spray ◽  
Zno Nanocrystals ◽  
Order Diffraction ◽  
Different Temperatures

ABSTRACTScanning electronic microscopy (SEM), X ray diffraction (XRD) and photoluminescence (PL) have been applied to the study of structural and optical properties of ZnO nanocrystals prepared by the ultrasonic spray pyrolysis (USP) at different temperatures. The variation of temperatures and times at the growth of ZnO films permits modifying the ZnO phase from the amorphous to crystalline, to change the size of ZnO nanocrystals (NCs), as well as to vary their photoluminescence spectra. The study has revealed three types of PL bands in ZnO NCs: defect related emission, the near-band-edge (NBE) PL, related to the LO phonon replica of free exciton (FE) recombination, and its second-order diffraction peaks. The PL bands, related to the LO phonon replica of FE, and its second-order diffraction in the room temperature Pl spectrum testify on the high quality of ZnO films prepared by the USP technology.

scholarly journals Optimization of the Cathode Arc Plasma Deposition Processing Parameters of ZnO Film Using the Grey-Relational Taguchi Method

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Shuo-Fu Hsu ◽  
Jyh-Horng Chou ◽  
Chun-Hsiung Fang ◽  
Min-Hang Weng
Keyword(s):  
Electrical Resistivity ◽  
Taguchi Method ◽  
Plasma Deposition ◽  
Optical Transmittance ◽  
Processing Parameters ◽  
Zno Thin Films ◽  
Zno Films ◽  
Arc Plasma ◽  
Cathode Arc ◽  
Grey Relational

We deposited undoped ZnO films on the glass substrate at a low temperature (<70°C) using cathode arc plasma deposition (CAPD) and the grey-relational Taguchi method was used to determine the processing parameters of ZnO thin films. The Taguchi method with an L9 orthogonal array, signal-to-noise (S/N) ratio, and analysis of variance (ANOVA) is employed to investigate the performances in the deposition operations. The effect and optimization of deposition parameters, comprising the Ar : O2gas flow ratio of 1 : 6, 1 : 8, and 1 : 10, the arc current of 50 A, 60 A, and 70 A, and the deposition time of 5 min, 10 min, and 15 min, on the electrical resistivity and optical transmittance of the ZnO films are studied. The results indicate that, by using the grey-relational Taguchi method, the optical transmittance of ZnO thin films increases from 88.17% to 88.82% and the electrical resistivity decreases from5.12×10-3Ω-cm to4.38×10-3Ω-cm, respectively.

Zinc Oxide Thin Films with Reduced Native Compensative Defects Grown by Ultrasonic Spray Pyrolysis at Atmosphere

2007 ◽  
Vol 336-338 ◽  
pp. 589-592
Author(s):  
Jian Ling Zhao ◽  
Xiao Min Li ◽  
Ji Ming Bian ◽  
Wei Dong Yu ◽  
C.Y. Zhang
Keyword(s):  
Spray Pyrolysis ◽  
Deep Level ◽  
Hole Concentration ◽  
Ultrasonic Spray Pyrolysis ◽  
Zno Films ◽  
Near Band Edge ◽  
Dense Microstructure ◽  
Ultrasonic Spray ◽  
High Hole Concentration ◽  
P Type

ZnO films were deposited on Si (100) substrate by ultrasonic spray pyrolysis at atmosphere. The film grown at optimum conditions is well crystallized with uniform, smooth and dense microstructure. Photoluminescence measurement shows a strong near band edge UV emission at 379nm and an almost undetectable deep-level emission band centered at 502nm. The resistivity of ZnO film is reduced by an order after N-In codoping, which produces p-type conduction with high hole concentration and hall mobility.

Photoluminescence of ZnO Nanocrystals Embedded in BaF2 Matrices by Magnetron Sputtering

2008 ◽  
Vol 8 (3) ◽  
pp. 1160-1164
Author(s):  
C. H. Zang ◽  
Y. C. Liu ◽  
R. Mu ◽  
D. X. Zhao ◽  
J. Y. Zhang ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Raman Scattering ◽  
Free Exciton ◽  
Wide Band ◽  
Zno Films ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Ultraviolet Emission ◽  
Pl Spectra ◽  
Zno Nanocrystals

This paper describes ZnO nanocrystals embedded in BaF2 matrices by the magnetron sputtering method in an attempt to use fluoride as a shell layer to embed ZnO nanocrystals core. BaF2 is a wide-band gap material, and can confine carriers in the ZnO films. As a result, the exciton emission intensity should be enhanced. The sample was annealed at 773 K, and X-ray diffraction (XRD) results showed that ZnO nanocrystals with wurtzite structure were embedded in BaF2 matrices. Raman-scattering spectra also confirmed the formation of ZnO nanoparticles. Abnormal longitudinal-optical (LO) phonon-dominant multiphonon Raman scattering was observed in the sample. Room-temperature photoluminescence (PL) spectra showed an ultraviolet emission peak at 374 nm. The origin of the ultraviolet emission is discussed here with the help of temperature-dependent PL spectra. The ultraviolet emission band was a mixture of free exciton and bound exciton recombination observed in the low temperature PL spectra (at 77 K). Abnormal temperature dependence of ultraviolet near-band-edge emission-integrated intensity of the sample was observed. The band tail state was observed in the absorption spectra, illustrating that the impurity-related defects were caused by the shell of the BaF2 grain layer. For comparison, ZnO films on BaF2 substrates were also fabricated by the magnetron sputtering method, and the same measurement methods were used.

Lasing Characteristics of Nano-structured Zinc Oxide

2006 ◽  
Vol 957 ◽  
Author(s):  
Shou-Yi Kuo ◽  
Wei-Chun Chen ◽  
Fang-I Lai
Keyword(s):  
Electron Microscope ◽  
Room Temperature ◽  
Free Exciton ◽  
Laser Action ◽  
Hexagonal Structure ◽  
Zno Films ◽  
Near Band Edge ◽  
Lasing Characteristic ◽  
Pl Spectra ◽  
Reported Data

ABSTRACTHighy-quality nano-structured ZnO samples have been synthesized by simple chemical solution and post-thermal treatment. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), temperature-dependent photoluminescence (PL) spectra measurements. XRD patterns illustrated that there were no second phases in these ZnO samples, and the TEM results indicated that the ZnO samples are single crystalline with a hexagonal structure. Room-temperature PL spectra of ZnO thin films showed a strong UV near-band-edge (NBE) emission located at about 390 nm and a green defect-related (G) emissions, where the intensity ratio (INBE/IG) varies with the annealing temperatures. Meanwhile, the ZnO samples exhibited free exciton and very sharp exciton emissions at low temperatures. Particularly, room-temperature UV random lasing characteristic of ZnO films has been observed as well. It is shown that these nano-structured ZnO samples can exhibit random laser action depending on the growth condition. The threshold intensity for the lasing is comparable to earlier reported data. These results indicate that nano-structured ZnO samples prepared by simple techniques may be a promising material for further photonic devices. Possible lasing mechanism is discussed and further investigation to clarify the mechanism between the nano-structured ZnO samples is still underway.

Substrate Temperature Effects on the Structural and Optical Properties of TiO2-Doped ZnO Films for Organic Photovoltaic Devices

2013 ◽  
Vol 275-277 ◽  
pp. 1964-1967 ◽  
Author(s):  
T. Zhang ◽  
Z.Y. Zhong ◽  
J. Zhou ◽  
F.L. Sun
Keyword(s):  
Optical Properties ◽  
Substrate Temperature ◽  
Crystallite Size ◽  
Rf Magnetron Sputtering ◽  
Optical Transmittance ◽  
Optical Bandgap ◽  
Zno Films ◽  
Glass Substrates ◽  
Doped Zno ◽  
Deposited Films

TiO2-doped ZnO thin films with highly (002)-preferred orientation were grown on glass substrates by RF magnetron sputtering. The effect of substrate temperature on structure and optical properties of the films were investigated by X-ray diffractometer and spectrophotometer. The results show that the polycrystalline TiO2-doped ZnO films consist of the hexagonal crystal structures with c-axis as the preferred growth orientation normal to the substrate. The substrate temperature significantly affects the crystallite size and optical transmittance of the deposited films, but slightly influences the refractive index and optical bandgap of the deposited films. The TiO2-doped ZnO film grown at substrate temperature of 470 K possesses the maximum crystallite size, an average transmittance of 76.2 % in the visible light range, and an optical bandgap of 3.46 eV.

Enhanced p-Type ZnO Films through Nitrogen and Argentum Codoping Grown by Ultrasonic Spray Pyrolysis

2008 ◽  
Vol 25 (9) ◽  
pp. 3400-3402 ◽  
Author(s):  
Wang Jing-Wei ◽  
Bian Ji-Ming ◽  
Liang Hong-Wei ◽  
Sun Jing-Chang ◽  
Zhao Jian-Ze ◽  
...  
Keyword(s):  
Spray Pyrolysis ◽  
Ultrasonic Spray Pyrolysis ◽  
Zno Films ◽  
Ultrasonic Spray ◽  
P Type

scholarly journals Influence of the First Preparation Steps on the Properties of GaN Layers Grown on 6H-SiC by MBE

1999 ◽  
Vol 4 (S1) ◽  
pp. 310-315 ◽  
Author(s):  
R. Lantier ◽  
A. Rizzi ◽  
D. Guggi ◽  
H. Lüth ◽  
B. Neubauer ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Free Exciton ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Edge Emission ◽  
Rocking Curve ◽  
A Value ◽  
Dislocations Density ◽  
Aln Buffer ◽  
Atomically Flat

The Gan heteroepitaxy on 6H-SiC is affected by the bad morphology of the substrate surface. We performed a hydrogen etching at 1550oC on the 6H-SiC(0001) substrates to obtain atomically flat terraces. An improvement of the structural properties of GaN grown by MBE on such substrates after deposition of a LT-AlN buffer layer is observed. A value of less than 220 arcsec of the FWHM of the XRD rocking curve, showing a reduced screw dislocations density, is comparable with the best results reported until now for thick GaN samples. Photoluminescence showed a structured near band edge emission spectrum with evidence of the A, B and C free exciton recombinations.

scholarly journals Влияние температуры фотонного отжига на структурные и оптические свойства пленок ZnO, синтезированных методом дуального магнетронного распыления

2019 ◽  
Vol 53 (2) ◽  
pp. 267
Author(s):  
С.В. Зайцев ◽  
В.С. Ващилин ◽  
В.В. Колесник ◽  
М.В. Лимаренко ◽  
Д.С. Прохоренков ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Crystallite Size ◽  
Annealing Temperature ◽  
Optical Transmittance ◽  
Degree Of Crystallinity ◽  
Zno Films ◽  
Gas Atmosphere ◽  
Oxygen Gas ◽  
Microstructure Density ◽  
The Degree Of Crystallinity

AbstractZinc-oxide films 1.4 μm in thickness are deposited onto glassy substrates by the dual magnetron-assisted sputtering of zinc targets in an argon and oxygen gas atmosphere. The dependences of the structural and optical characteristics of the ZnO films on the temperature of postdeposition photonic annealing are studied. It is established that an increase in the annealing temperature yields an increase in the degree of crystallinity of the films. Electron microscopy shows that the deposited ZnO coatings are columnar in structure and the microstructure density and crystallite size increase upon annealing. It is found that, at an annealing temperature of 450–650°C, the optical transmittance increases to >90% in the spectral range 400–1100 nm. The experimental results show that the temperature of vacuum photonic annealing has the most profound effect on the final properties of ZnO coatings.

Enhancement of near-band-edge photoluminescence from ZnO films by face-to-face annealing

2003 ◽  
Vol 259 (4) ◽  
pp. 335-342 ◽  
Author(s):  
Y.G. Wang ◽  
S.P. Lau ◽  
X.H. Zhang ◽  
H.H. Hng ◽  
H.W. Lee ◽  
...  
Keyword(s):  
Band Edge ◽  
Zno Films ◽  
Near Band Edge ◽  
Face To Face
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