Cesium doped and undoped ZnO nanocrystalline thin films: a comparative study of structural and micro‐Raman investigation of optical phonons
TL;DR: In this article, undoped and cesium-doped zinc oxide (ZnO) thin films have been applied to sapphire substrate (0001) using the sol-gel method.
Abstract: Undoped and cesium-doped zinc oxide (ZnO) thin films have been deposited on sapphire substrate (0001) using the sol–gel method. Films were preheated at 300 °C for 10 min and annealed at 600 and 800 °C for 1 h. The grown thin films were confirmed to be of wurtzite structure using X-ray diffraction. Surface morphology of the films was analyzed using scanning electron microscopy. The photoluminescence (PL) spectra of ZnO showed a strong ultraviolet (UV) emission band located at 3.263 eV and a very weak visible emission associated with deep-level defects. Cesium incorporation induced a blue shift of the optical band gap and quenching of the near-band-edge PL for nanocrystalline thin film at room temperatures because of the band-filling effect of free carriers. A shift of about 10–15 cm−1 is observed for the first-order longitudinal-optical (LO) phonon Raman peak of the nanocrystals when compared to the LO phonon peak of bulk ZnO. The UV resonant Raman excitation at RT shows multiphonon LO modes up to fifth order. Copyright © 2010 John Wiley & Sons, Ltd.
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TL;DR: In this paper, a relaxation in the q-vector selection rule for the excitation of the Raman active optical phonons was proposed to increase the red shift and broadening of the signal from microcrystalline silicon films.
Abstract: The red shift and the broadening of the Raman signal from microcrystalline silicon films is described in terms of a relaxation in the q-vector selection rule for the excitation of the Raman active optical phonons. The relationship between width and shift calculated from the known dispersion relation in c-Si is in good agreement with available data. An increase in the decay rate of the optical phonons predicted on the basis of the same model is confirmed experimentally.
105 citations
TL;DR: In this paper, a facile all-solution approach for the growth of nanostructured p-CuO and n-ZnO thin films was reported, which showed rectification behavior with a turn on voltage of 2.5 V and an ideality factor of 3.15.
Abstract: We report a facile all-solution approach for the growth of nanostructured p-CuO and n-ZnO thin films. The influence of annealing temperature on the physical properties of CuO and ZnO thin films was examined. XRD and Raman spectra depict the structural and phase purity of solution grown CuO and ZnO films. The electrical as well as the optical properties of thin films were also studied. The average optical transmission of CuO and ZnO thin films in the visible spectral region was found to be above 80 and 95% respectively. Band gap energy variations on annealing temperature were investigated for CuO as well as ZnO films. Surface morphology analyzed by FESEM shows that the films are very smooth. All solution grown p-n heterojunction using p-CuO and n-ZnO films was fabricated in the structure ITO/n-ZnO/p-CuO/Au which showed rectification behavior with a turn on voltage of 2.5 V and an ideality factor of 3.15.
61 citations
Cites background from "Cesium doped and undoped ZnO nanocr..."
...The A1 (LO) peak at 547 cm 1 is associated from smaller scattering cross sections [70] while the Raman peak at 213 cm 1 represent the phonon scattering from 2E2 (low) mode [66,70] and that of 645 cm 1 is the acoustic overtone with A1 symmetry [71]....
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...The non polar E2 modes have two wave numbers, specifically, E2 (high) and E2 (low) related with the motion of oxygen and Zn sub lattice respectively [66]....
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TL;DR: In this article, a review extensively focused on the comprehensive cross-section of ZnO's luminescent, structural, optical, magnetic properties and various applications, with the key directions of development, serving as beginning, an orientation, and stimulation for upcoming research.
54 citations
TL;DR: In this article, two highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N4,N6-dibutyl-1,3,5-triazine-4,6diamine probe were synthesized via normal synthetic routes.
Abstract: Two novel highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N4,N6-dibutyl-1,3,5-triazine-4,6-diamine probe were synthesized via normal synthetic routes Both dendrimers (TPAD1 and TPAD2) form H-bonded donor–acceptor–donor (D–A–D) supramolecular triads TPAD1-PBI-TPAD1 and TPAD2-PBI-TPAD2 with 3,4,9,10-perylene tetra carboxylic diimide derivative (PBI) The presence of multiple H-bonds in the solution state was elucidated by 1H NMR titrations and IR spectral studies J-aggregations and electron/energy transfers provided by both dendrimers were verified by UV–Vis and photoluminescence (PL) titrations with PBI and the particle sizes of supramolecular triads were calculated by X-ray diffraction (XRD) analysis Similarly, both dendrimers also showed sensitivities towards Cu2+ in comparison with 19 interfering metal ions, which were evidenced via UV–Vis and PL titraions in both single and dual metal systems The maximum detection limit of Cu2+ ions was determined to be 20 ppm from PL titrations for both dendrimers, and the 1 : 2 stoichiometry of the complexes formed by both dendrimers (TPAD1-Cu2+ and TPAD2-Cu2+) were calculated by Job plots based on UV–Vis absorption titrations More importantly, the binding mechanism of the 1,3,5-triazine-4,6-diamine probe of both dendrimers was well characterized by 1H and 13C NMR titrations ([D8]THF : D2O = 2 : 1 in vol) and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially
48 citations
TL;DR: Ruthenium (Ru = 0, 1% and 2%) doped nano-crystalline zinc oxide (ZnO) nanorods were synthesized by using well-known sol-gel technique as discussed by the authors.
38 citations
References
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TL;DR: In this article, the authors explore the interrelationships between the green 510 nm emission, the free-carrier concentration, and the paramagnetic oxygen vacancy density in commercial ZnO phosphors by combining photoluminescence, optical absorption, and electron paramagnetic resonance spectroscopies.
Abstract: We explore the interrelationships between the green 510 nm emission, the free‐carrier concentration, and the paramagnetic oxygen‐vacancy density in commercial ZnO phosphors by combining photoluminescence, optical‐absorption, and electron‐paramagnetic‐resonance spectroscopies. We find that the green emission intensity is strongly influenced by free‐carrier depletion at the particle surface, particularly for small particles and/or low doping. Our data suggest that the singly ionized oxygen vacancy is responsible for the green emission in ZnO; this emission results from the recombination of a photogenerated hole with the singly ionized charge state of this defect.
3,487 citations
TL;DR: In this paper, a relaxation in the q-vector selection rule for the excitation of the Raman active optical phonons was proposed to increase the red shift and broadening of the signal from microcrystalline silicon films.
2,059 citations
TL;DR: In this article, the effect of the exact shape of the microcrystal and the relationship between the width, shift and asymmetry of the Raman line is calculated and is in good agreement with available experimental data.
1,957 citations
TL;DR: In this paper, the frequency and symmetry character of the fundamental modes of the Raman effect in zinc oxide has been determined using the continuous helium-neon and ionized argon lasers as sources.
Abstract: The Raman effect in zinc oxide has been measured using the continuous helium-neon and ionized argon lasers as sources. The frequency and symmetry character of the fundamental modes have been determined. The results are: two ${E}_{2}$ vibrations at 101 and 437 ${\mathrm{cm}}^{\ensuremath{-}1}$; one transverse ${A}_{1}$ at 381 ${\mathrm{cm}}^{\ensuremath{-}1}$ and one transverse ${E}_{1}$ at 407 ${\mathrm{cm}}^{\ensuremath{-}1}$; one longitudinal ${A}_{1}$ at 574 ${\mathrm{cm}}^{\ensuremath{-}1}$ and one longitudinal ${E}_{1}$ at 583 ${\mathrm{cm}}^{\ensuremath{-}1}$.
1,757 citations
TL;DR: In this paper, a quantitative theory for the shapes of the absorption bands of F -centres is given on the basis of the Franck-Condon principle, and it is shown that the absorption constant as a function of frequency and temperature can be expressed in terms of Bessel functions with imaginary arguments.
Abstract: A quantitative theory for the shapes of the absorption bands of F -centres is given on the basis of the Franck-Condon principle. Underlying the treatment are two simplifying assumptions: namely, ( a ) that the lattice can be approximately treated as a dielectric continuum; ( b ) that in obtaining the vibrational wave functions for the lattice, the effect of the F -centre can be considered as that of a static charge distribution. Under these assumptions, it is shown that the absorption constant as a function of frequency and temperature can be expressed in terms of the Bessel functions with imaginary arguments. The theoretical curves for the absorption constant compare very favourably with the experimental curves for all temperatures. Also considered in the paper are the probabilities of non-radiative transitions, which are important in connexion with the photo-conductivity observed following light absorption by F -centres. The treatment given differs from the qualitative considerations hitherto in one important aspect, namely, the strength of the coupling between the electron and the lattice is taken into account. The adiabatic wave functions for the F -centre electron required for the discussion are obtained by perturbation methods. The probability for an excited F -centre to return to its ground state by non-radiative transitions is shown to be negligible; similar transitions to the conduction band are, however, important if the excited state is separated from the conduction band by not much more than 0·1 eV. The temperature dependence of such transitions is complicated, but, for a wide range of temperatures, resembles e - w/k T . Tentative estimates show that the result is Consistent with the observed steep drop of the photo-conductive current with temperature.
1,314 citations