Excitonic emissions observed in ZnO single crystal nanorods

Park, Won Il; Jun, Yin; Jung, Sungmoon; Yi, Gyu‐Chul

doi:10.1063/1.1544437

Cited by 445 publications

(293 citation statements)

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“…29͒ to 383 nm, 30 and the exact energy position depends on the contribution between the free exciton and the transition between free electrons to acceptor bound holes. [31][32][33][34] The deep level emission band has previously been attributed to several defects in the crystal structure such as 42 and extrinsic impurities such as substitutional Cu. 43 Recently, this deep level emission band had been identified and at least two different defect origins ͑V O and V Zn ͒ with different optical characteristics were claimed to contribute to this deep level emission band.…”

Section: Resultsmentioning

confidence: 99%

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Yang

Zhao

Willander

et al. 2009

Journal of Applied Physics

128

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Vertically well-aligned ZnO nanorods on Si substrates were prepared by a two-step chemical bath deposition method. The structure and optical properties of the grown ZnO nanorods were investigated by Raman and photoluminescence spectroscopy. The results showed that after an annealing treatment at around 500°C in air atmosphere, the crystal structure and optical properties became much better due to the decrease in surface defects. The resonant Raman measurements excited by 351.1 nm not only revealed that the surface defects play a significant role in the as-grown sample, which was supported by low temperature time-resolved photoluminescence measurements, but also suggested that the strong intensity increase in some Raman scatterings was due to both outgoing resonant Raman scattering effect and deep level defect scattering contribution for ZnO nanorods annealed from 500 to 700°C.

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Section: Resultsmentioning

confidence: 99%

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Yang

Zhao

Willander

et al. 2009

Journal of Applied Physics

128

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“…[13][14][15] It is also notable that the dominant emission of our GaN nanowires grown by Ni-catalyst-assisted MOVPE was observed at 3.437 eV with additional peaks at 3.472 and 3.266 eV although the dominant emission peak of GaN nanowires previously grown by other groups has previously been observed at 3.2-3.35 eV. [3][4][5][6]8 As mentioned above, the PL peaks at 3.472 and 3.266 eV are commonly observed from many epitaxial films grown by MOVPE, associated with defects presumably due to the same growth process. Meanwhile, the new PL peak at 3.437 eV is not well known for epitaxial GaN films, so it may result from Ni-related defects.…”

mentioning

confidence: 92%

“…7 Meanwhile, optical characterization methods such as photoluminescence ͑PL͒ spectroscopy requiring no physical contacts are useful for defect characterization of the nanomaterials. 8 In particular, low temperature PL spectroscopy is a very sensitive and nondestructive tool for characterizing radiative defects in semiconductors. 9 Although a few papers on synthesis and PL spectra of GaN nanowires have previously been reported, 10 near-band-edge ͑NBE͒ PL peak positions from catalyst-assisted grown GaN nanowires have not been consistent with those of epitaxial thin films.…”

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confidence: 99%

Photoluminescent characteristics of Ni-catalyzed GaN nanowires

Yoo

Hong

et al. 2006

Applied Physics Letters

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The authors report on time-integrated and time-resolved photoluminescence ͑PL͒ of GaN nanowires grown by the Ni-catalyst-assisted vapor-liquid-solid method. From PL spectra of Ni-catalyzed GaN nanowires at 10 K, several PL peaks were observed at 3.472, 3.437, and 3.266 eV, respectively. PL peaks at 3.472 and 3.266 eV are attributed to neutral-donor-bound excitons and donor-acceptor pair, respectively. Furthermore, according to the results from temperature-dependent and time-resolved PL measurements, the origin of the PL peak at 3.437 eV is also discussed. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2243710͔One-dimensional GaN nanostructures including nanowires, nanorods, and nanotubes have recently attracted much attention because of their potential applications for optoelectronic devices in the nanoscale. 1,2 GaN nanowires have been synthesized by many different nanowire growth methods. [3][4][5][6] Among numerous nanowire synthesis methods, the metal catalyst-assisted vapor-liquid-solid ͑VLS͒ growth method has been widely employed because this technique offers easy and size-controllable growth of many semiconductor nanowires. However, since the metal catalysts used for nanowire growth may act as impurities in the nanomaterial and even a small amount of impurities in semiconductors can significantly change physical properties of the host materials, it is very important to characterize the impurities and defects in catalyst-assisted grown semiconductor nanomaterials. The effect of impurities and defects on the physical properties of host materials is also expected to increase with a reduction in the size of the materials. In addition, the unintentionally doped impurities in semiconductors make it difficult to accurately control their conductivities and optical properties. Nevertheless, the defect characterization of catalyst-assisted grown semiconductor nanowires has rarely been reported because of difficulties in elemental analysis and electrical device fabrications. 7 Meanwhile, optical characterization methods such as photoluminescence ͑PL͒ spectroscopy requiring no physical contacts are useful for defect characterization of the nanomaterials. 8 In particular, low temperature PL spectroscopy is a very sensitive and nondestructive tool for characterizing radiative defects in semiconductors. 9 Although a few papers on synthesis and PL spectra of GaN nanowires have previously been reported, 10 near-band-edge ͑NBE͒ PL peak positions from catalyst-assisted grown GaN nanowires have not been consistent with those of epitaxial thin films. 5,6 Furthermore, time-resolved PL ͑TRPL͒ spectroscopy enables the investigation of exciton lifetime, an important parameter related to defects in materials and device performance. Despite the importance of TRPL measurements, TRPL behavior in GaN nanowires has rarely been reported. 11 In this letter, we report on both time-integrated and time-resolved photoluminescent properties of GaN nanowires grown by the Nicatalyst-assisted VLS method.GaN nanowires were grown on a 2-nm-...

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“…The main peak is at 378 nm and there is no yellow luminescence related to deep levels. 13 The emissions due to deep levels associated with defects in ZnO is often observed in other ZnO nanostructures, 14 but our ZnO nanodisks showed strong band-edge emissions with no deep level emissions affiliated with defects, implying that our ZnO nanodisks have good crystal quality and are more appropriate for photonic nanodevices.…”

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confidence: 99%

Whispering-gallery-modelike-enhanced emission from ZnO nanodisk

Kim

Jang

et al. 2006

Applied Physics Letters

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Hexagonal nanodisks of ZnO were fabricated by a solution process using ZnO nanoparticles and their cathodoluminescence characteristics were investigated. Monochromatic cathodoluminescence images showed that luminescence was spatially localized near the boundary of the nanodisk and spectral analysis in conjunction with the intensity profile consistently ascribed the spatial localization of luminescence to whispering-gallery-modelike-enhanced emission. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2174122͔With the successful demonstration of various nanostructures and increasing demand for integrable optoelectronic components with existing silicon technology, small-scale dielectric resonators applicable to photonic nanodevices with low-thresholds have gained importance because they can be used as low-power-consumption light sources in integrated circuits. Reducing the size of photonic devices, however, results in decrease of luminescence intensity in such a way that careful design of intensity enhancement mechanism should be introduced. For this reason, the whispering-gallery mode, which has been particularly utilized in applications to optical communication, has attracted much attention because it is a very efficient mechanism of luminescence enhancement even in small-scale resonators. 1-4 Since a top-down approach, such as lithography, has been among the best technological methods to fabricate tailored nanostructures appropriatue for specific research or application purposes, much effort has been made in order to fabricate nanoresonators via lithography to achieve low-threshold photonic nanodevices. There are, however, a few important generic problems in top-down fabrication of nanoresonators. There is unavoidable damage to films associated with lithographic etching process. An unwanted strain effect is also involved due to the limited choice of substrates to accommodate lattice misfit. In contrast, photonic nanodevices with bottom-up-based nanoscale resonant cavity employing whispering-gallery modes ͑WGMs͒ are very promising integrable components with high luminescence efficiency. More than that, a bottom-up approach typically does not depend on the choice of substrates, which is a major advantage in integration with current silicon technology.Due to direct and wide-band-gap characteristics with a large binding exciton energy, ZnO has drawn much attention for potential application to short-wavelength optoelectronic devices. In addition to single-crystalline ZnO thin films, ZnO nanowires and nanorods with perfect crystallinity were recently fabricated, and newly developed ZnO-based nanostructures demonstrated the possibility for nanoscale optoelectronic devices. [5][6][7] In contrast with one-dimensional nanostructures, such as nanorods, hexagonal nanodisk resonators employing WGMs have a smaller effective volume of gain medium, so that it is easier to fabricate compact photonic nanodevices. In addition, nanodisks are more confined to the surface of substrate and mechanical stability of nanodisks for pos...

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Excitonic emissions observed in ZnO single crystal nanorods

Cited by 445 publications

References 23 publications

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Annealing effects on optical properties of low temperature grown ZnO nanorod arrays

Photoluminescent characteristics of Ni-catalyzed GaN nanowires

Whispering-gallery-modelike-enhanced emission from ZnO nanodisk

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