Nature of red luminescence in oxygen treated hydrothermally grown zinc oxide nanorods (original) (raw)
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Materials Chemistry and Physics, 2006
ZnO nanorods had been successfully prepared by annealing the precursors, which are produced by the chemical precipitation method. The annealing temperature is found to be a key parameter for the preparation of ZnO nanorods. The largest ratio of the length to diameter for nanorods has been obtained at the annealing temperature of 400 • C. The microstructure of the resultant nanorods was studied by means of X-ray diffraction, transmission electron microscopy and photoluminescence spectra. The UV and visible emission are observed at room temperature. Spectra analyses show that the green emission depends strongly on the annealing temperature. The green and the yellow emission are attributed to the single ionized oxygen vacancy Vo + and the interstitial oxygen O i − , respectively.
Chemical Physics Letters, 2011
A novel approach for enhancing the ultraviolet emission properties of ZnO nanorods (NRs) using a in situ facile hydrothermal technique in the presence of excess zinc metal in addition to zinc acetate in the precursor has been demonstrated. The photoluminescence studies show a higher ultra-violet (UV) emission (I UV /I VIS 38)intheNRsgrownwith15mMexcesszincmetalcomparedtothat(IUV/IVIS38) in the NRs grown with 15 mM excess zinc metal compared to that (I UV /I VIS 38)intheNRsgrownwith15mMexcesszincmetalcomparedtothat(IUV/IVIS5.5) of the NRs grown without excess metal. Electron paramagnetic resonance studies reveal a higher intensity signal at g $1.95 for NRs grown with 15 mM excess zinc indicating the presence of paramagnetic Zn i in higher concentration.
Photoluminescence of ZnO nanorods prepared by hydrothermal method
Journal of Physics: Conference Series, 2019
In this research, the effects of calcination temperature and reaction time on the photoluminescent properties of ZnO nanorods prepared by hydrothermal processes were studied. Morphology, crystalline structure and photoluminescent properties of the prepared samples were analyzed by scanning electron microscope (SEM), X-ray diffractrometer (XRD) and fluorescent spectrophotometer. The study found that a reaction time of 5 hours on a glass slide and calcination at 500°C was the best preparation condition. The prepared ZnO nanorods were aligned without direction and distributed throughout the substrate. The average diameter of the prepared ZnO nanorods was 91.96 ± 21.16 nm. The prepared ZnO nanorods comprised a hexagonal crystalline structure with an emission peak in the UV range.
Effects of postgrowth annealing treatment on the photoluminescence of zinc oxide nanorods
Journal of Applied Physics, 2006
Postgrowth annealing was carried out to investigate the photoluminescence of zinc oxide ͑ZnO͒ nanorods synthesized using a thermal chemical vapor deposition method. The observed change in photoluminescence after the annealing processes strongly suggests that positively charged impurity ions or interstitial Zn ions are the recombination centers for green luminescence observed in the present sample. A model based on the interplay between the band bending at the surface and the migration of positively charged impurity ions or Zn ions was proposed, which satisfactorily explains the observed photoluminescence.
Visible Luminescence from ZnO Nanostructures
MRS Proceedings, 2006
ABSTRACTRoom temperature photoluminescence (PL) spectra from zinc oxide (ZnO) nanostructures were studied. ZnO samples were produced via thermal chemical vapor deposition (thermal-CVD) and a variety of ZnO nanostructures were synthesized by adjusting the oxygen content during the growth process. All samples exhibit a sharp and strong ultra-violet near-band-edge (NBE) emission at about 3.18 eV. The visible emission from the samples deposited under an oxygen-deficient condition were dominated by blue-green band emission at 2.34 eV. The intensity of the blue-green band was greatly reduced (so-called green band free) for the ZnO deposited at the center of the wafer while strong violet-blue emission bands and broad bands at yellow-orange-red range were collected from the ZnO grown along the edge of the wafer. We believe that the spatial inhomogeniety was caused by turbulent gas flow in the reaction chamber, which resulted in different local oxygen concentration. Origin of visible lumines...
Substrate effect of hydrothermally grown ZnO nanorods and its luminescence properties
Journal of Experimental Nanoscience, 2012
We report the hexagonal wurtzite crystalline structure of ZnO nanorod growth by hydrothermal chemical wet synthesis at low temperature (90°C). We have used p-Si (100), n-Si (100), α-quartz (0001), MgO (0001) and ITO (polycrystalline) substrates to understand the growth mechanism of ZnO nanorods with a low pressure environment. X-ray diffraction study confirms the hexagonal structure of the ZnO nanorod. Scanning electron microscopy (SEM) also shows the hexagonal structure along with different size and width of the nanorods. The substrate effect of nanorods has been explained on the basis of adatom kinetics during the growth. We observed that the nanorods were grown from a single nucleation point with 4–5 different branches on the ITO substrate with uniform length and width, whereas MgO substrate shows curled flower architecture across the whole area. The photoluminescence illustrates strong substrate effect. A wide range of UV emission bands along with visible emission has been observed from the ZnO nanorods deposited on different substrates.
Synthesized ZnO nanorod with different range of morphologies using a simple hydrothermal method
INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2019, 2020
Zinc oxide nanorods have been synthesized by a hydrothermal method using a two different synthesis condition at low temperature. First sample have been grown at 122 C° temperature for 4 hours in the autoclave then at room temperature for two days and the second sample have been synthesized at 122C° for 4 hours in autoclave only. All products have been checked by using UV-Visible absorption and photoluminescence (PL), and the morphology have been studied by (FE-SEM), and AFM. In this work have been synthesized the hexanol nanorods (HZNR) at 122C° temperature for 4 hours in autoclave, while the Zinc oxide nanorod (ZNR) have been growth at 122C° for 4 hours in autoclave then two days at room temperature. UV-visible spectra show increased at excitonic absorption peaks in visible region with HZNR more than ZNR. All samples were observed that had high absorption in UV regain of spectra. Energy gup (Eg) degreased at HZNR (3) eV compared with ZNR (3.2) eV. In PL spectra, the band visible emission peaks were observed for all synthesized products (HZNR &ZNR) at 430 and 480 nm and high intense band centers at 688 for ZNR and 670 for HZNR However, the PL intensity peaks were reduced at (670 nm) for (HZNR) sample. the morphology of the sample was different when the temperature was changed. a hydrothermal method is uncomplicated, simple, cheap and environmentally, which made it favorable for huge-scale preparation for design and other application.
Thermal annealing studies of the deep level emission in solution-grown zinc oxide nanorods
Applied Physics A, 2017
In this report, the effects of thermal annealing on the room temperature (RT) photoluminescence characteristics of solution-grown ZnO nanorods (ZNs) are presented. It is shown that the near surface regions of asgrown ZNs are rich in Zn. Within the detection limit of X-ray photoelectron spectroscopy (XPS), it is confirmed that the environment of annealing affects indeed the activation of intrinsic defects. Furthermore, thermal treatment at high temperatures removes H-related defects as expected; and this removal process is found to affect significantly the RT luminescence properties of ZNs, especially when ZNs are annealed sequentially from 300 °C to ~700 °C. Specifically, the passivation of vacancy-related defects by H is demonstrated following thermal treatment in this temperature range. Finally, the green luminescence (~500 nm) that evolves following annealing above ~800 °C is assigned to Zn vacancy defects.
Journal of Crystal Growth, 2006
In this study, we investigated the effect of post-annealing treatment on the UV photoluminescence of ZnO nanorods deposited on (0 0 0 1) GaN by hydrothermal synthesis. The temperature dependence of the photoluminescence spectra of ZnO nanorods annealed in nitrogen and oxygen was also studied. The as-grown ZnO nanorods were annealed in nitrogen and oxygen at 800 1C in 30 min. Results showed that UV light emission was greatly enhanced by annealing the as-grown ZnO nanorods in nitrogen ambient. Meanwhile, strong visible light emission was observed from the ZnO nanorods annealed in oxygen ambient. The effect of the annealing ambient and the photoluminescence temperature dependence were discussed with the relations to the structural defects. The time-resolved photoluminescence measurement was also proceeded to characterize the optical quality of the annealed ZnO nanorods. The decay times were 74 and 84 ps for oxygen and nitrogen annealed ZnO nanorods, respectively. Once again, these results confirmed that the nitrogen annealed ZnO nanorods had better optical quality with less nonradiative related defects.