Structural and optical properties of single-crystalline ultraviolet-emitting needle-shaped ZnO nanowires

Umar, Ahmad; Kim, S.H.; Kim, J.H.; Park, Y.K.; Hahn, Yoon‐Bong

doi:10.1016/j.matlet.2007.03.079

Cited by 15 publications

(10 citation statements)

References 29 publications

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“…An increase in the E 2 phonon frequency (blueshift) is ascribed to compressive stress, whereas a decrease in the E 2 phonon frequency (redshift) is ascribed to tensile stress [32]. A redshift in the E 2 high frequency could also be attributed to an increase in oxygen vacancies (V O ) [33,34], but this would be accompanied by a higher intensity of the LO phonon in the A 1 mode, which is around 575-580 cm -1 [18,35]. The tensile stress also increases the d-spacing which causes the peaks to shift in the X-Ray diffractogram towards lower 2ϑ values, whereas the compressive stress decreases the d-spacing, which results in the shifting of peaks towards higher 2ϑ values in the XRD pattern [17].…”

Section: Ramanmentioning

confidence: 99%

Room temperature sintering of polar ZnO nanosheets: II-mechanism

Fernández-Pérez

Rodríguez-Casado

Valdés-Solı́s

et al. 2017

Phys. Chem. Chem. Phys.

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In a previous work by the authors (A. Fernández-Pérez el al., Room temperature sintering of polar ZnO nanosheets: I-evidence, 2017, DOI: 10.1039/C7CP02306E), polar ZnO nanosheets were stored at room temperature under different atmospheres and the evolution of their textural and crystal properties during storage was followed. It was found that the specific surface area of the nanosheets drastically decreased during storage, with a loss of up to 75%. The ZnO crystals increased in size mainly through the partial merging of their polar surfaces at the expense of narrow mesoporosity, in a process triggered by the action of moisture, oxygen and, in their absence, by light. In the present work, a set of spectroscopic techniques (FTIR, Raman and XPS) has been used in an attempt to unravel the mechanism behind this spontaneous sintering process. The mechanism starts with the molecular adsorption of water, which takes place on Zn atoms close to oxygen vacancies on the (100) surface, where HO dissociates to form two hydroxyl groups and to heal one oxygen vacancy. This process triggers the room temperature migration of Zn interstitials towards the outer surface of the polar region. What were previously interstitial Zn atoms now gradually occupy the mesopores, with interstitial oxygen being used to build up the O sublattice until total occupancy of the narrow mesoporosity is achieved.

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Section: Ramanmentioning

confidence: 99%

Room temperature sintering of polar ZnO nanosheets: II-mechanism

Fernández-Pérez

Rodríguez-Casado

Valdés-Solı́s

et al. 2017

Phys. Chem. Chem. Phys.

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“…8 shows the Raman-scattering spectra for the asgrown ZnO nanostructures on silicon substrate with and without the hydrogen pretreatment step prior to the deposition. A sharp and strong peak in the range of 436.7-437.4 cm À1 , for all the cases, is attributed to the Raman-active E 2 mode and characteristic of hexagonal wurtzite phase of ZnO [23][24][25]. The appearance of a short and suppressed peak in all the spectra in the range of 578-581 cm À1 , assigned as E 1L , originated due to the impurities and formation of defects such as oxygen vacancies, zinc interstitial, free carriers, etc.…”

Section: Article In Pressmentioning

confidence: 77%

Effect of hydrogen pretreatment combined with growth temperature on the morphologies of ZnO nanostructures: Structural and optical properties

Umar

Kim

Suh

et al. 2007

Journal of Crystal Growth

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“…The Raman spectrum is characteristic of pure and well‐crystallized hexagonal wurtzite:20 it is mostly dominated by a sharp peak at 438 cm −1 attributed to the E 2H mode, but other weaker peaks are observed at 335, 381 and 1095 cm −1 , which correspond to the E 2H ‐E 2L , A 1T multiphonon contributions, and the acoustic combination of A 1 and E 2 modes, respectively. The absence of contribution around 578–583 cm −1 (A 1L and E 1L modes) reveals the absence of punctual defects such as interstitial zinc cations or oxygen vacancies, in the ZnO lattice 21. The spectra of the ZnO fibers indicate that ZnO structure remains unchanged upon extrusion, and that no significant defects associated to the extrusion process have been created.…”

Section: Resultsmentioning

confidence: 93%

ZnO/PVA Macroscopic Fibers Bearing Anisotropic Photonic Properties

Kinadjian

Achard

Julián‐López

et al. 2012

Adv Funct Materials

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Composite PVA/ZnO‐nanorods fibers, synthesized through co‐axial flux extrusion exhibit higher anisotropic photonic properties, both in absorption and emission, as a result of the collective alignment of the ZnO nanorods along the main axis of the PVA fiber. This photonic anisotropy is triggered by a synergistic interaction between the PVA matrix, stretched above the glass transition temperature (Tg), and cooled down under strain. Compared with non‐elongated fibers that present an isotropic emission, composite fibers previously submitted to a tensile stress absorb selectively UV emission when the polarized laser beam is parallel to the main axis of the fiber. In addition, their photolumincescence is also anisotropic, with a waveguide behavior along the main axis of the fiber. Mechanical properties of these composite fibers are also drastically improved, compared with pure PVA fibers: the longitudinal Young modulus of these fibers is increased from 2 to 6 GPa upon ZnO addition, a value similar to those already observed for composite fibers, prepared either with carbon nanotubes, or V2O5 macroscopic fibers.

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Structural and optical properties of single-crystalline ultraviolet-emitting needle-shaped ZnO nanowires

Cited by 15 publications

References 29 publications

Room temperature sintering of polar ZnO nanosheets: II-mechanism

Room temperature sintering of polar ZnO nanosheets: II-mechanism

Effect of hydrogen pretreatment combined with growth temperature on the morphologies of ZnO nanostructures: Structural and optical properties

ZnO/PVA Macroscopic Fibers Bearing Anisotropic Photonic Properties

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