Random lasing in ZnO nanocrystals

Fallert, J.; Dietz, R. J. B.; Hauser, Mario; Stelzl, Felix; Klingshirn, C.; Kalt, H.

doi:10.1016/j.jlumin.2009.02.022

Cited by 48 publications

(40 citation statements)

References 12 publications

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“…19,21,22 Robin et al 13 detected the Y 0 transition in ZnO nanowires with diameters of about 300 nm on GaN substrates but not on sapphire substrates, where the ZnO nanowires had a diameter of about 150 nm. In ZnO nanocrystals similar observations were reported by Fallert et al 15 Untreated ZnO nanocrystals with diameters between 70 and 120 nm did not exhibit the Y 0 transition. However, after annealing larger polycrystalline clusters with diameters up to 1 μm were formed and a pronounced Y 0 line could be observed.…”

Section: Introductionsupporting

confidence: 88%

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Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

et al. 2011

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ZnO single crystals, epilayers, and nanostructures often exhibit a variety of narrow emission lines in the spectral range between 3.33 and 3.35 eV which are commonly attributed to deeply bound excitons (Y lines). In this work, we present a comprehensive study of the properties of the deeply bound excitons with particular focus on the Y 0 transition at 3.333 eV. The electronic and optical properties of these centers are compared to those of the shallow impurity related exciton binding centers (I lines). In contrast to the shallow donors in ZnO, the deeply bound exciton complexes exhibit a large discrepancy between the thermal activation energy and localization energy of the excitons and cannot be described by an effective mass approach. The different properties between the shallow and deeply bound excitons are also reflected by an exceptionally small coupling of the deep centers to the lattice phonons and a small splitting between their two electron satellite transitions. Based on a multitude of different experimental results including magnetophotoluminescence, magnetoabsorption, excitation spectroscopy (PLE), time resolved photoluminescence (TRPL), and uniaxial pressure measurements, a qualitative defect model is developed which explains all Y lines as radiative recombinations of excitons bound to extended structural defect complexes. These defect complexes introduce additional donor states in ZnO. Furthermore, the spatially localized character of the defect centers is visualized in contrast to the homogeneous distribution of shallow impurity centers by monochromatic cathodoluminescence imaging. A possible relation between the defect bound excitons and the green luminescence band in ZnO is discussed. The optical properties of the defect transitions are compared to similar luminescence lines related to defect and dislocation bound excitons in other II-VI and III-V semiconductors.

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Section: Introductionsupporting

confidence: 88%

“…This line was reported in a multitude of different ZnO samples such as substrates, 3-6 homoepitaxial 7-9 and heteroepitaxial films, [10][11][12][13] microcrystals and nanocrystals, [14][15][16][17][18] nanowires, 19 and quantum wells. 20 In nanomaterials the Y 0 line is only observed in structures with sufficiently large dimensions.…”

Section: Introductionmentioning

confidence: 67%

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

et al. 2011

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“…The mean particle size is of the order of the effective wavelength in the medium [14,15]. This powder showed the lowest threshold for random lasing, compared to several other ones with lower or larger mean particle sizes [16]. Studies on the linear optical properties of these powders can be found in Refs.…”

mentioning

confidence: 98%

Random lasing in nanocrystalline ZnO powders

Kalt

Fallert

Dietz

et al. 2010

Physica Status Solidi (b)

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We investigate the properties of random lasing in nanocrystalline ZnO powders. The lowest threshold for lasing occurs for average particle diameters of about 260 nm. Reproducible lasing features are achieved for reduced ensemble sizes. Spatially resolved luminescence spectroscopy is used to probe directly the degree of localization of random laser mode. We find that strongly confined and extended modes can co-exist in the same spatial area. However, localized modes appear for small optical gain while extended modes are only supported in the presence of large optical gain, as is expected from theory.Localized and extended random-laser modes co-exist in space but appear in spectral regions of low and high optical gain, respectively.

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“…1 Because the only requirements are that the host medium be turbid and a gain medium be present, research has shown that this type of laser action can be observed in a range of scattering media such as laser and semiconductor powders, 2 nanocrystals, 3 and even biological tissues. 4 Not only is the physics underpinning these lasers rich, but they have great technological potential.…”

Section: Introductionmentioning

confidence: 99%

Lowering the excitation threshold of a random laser using the dynamic scattering states of an organosiloxane smectic A liquid crystal

Morris

Gardiner

Qasim

et al. 2012

Journal of Applied Physics

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Smectic A liquid crystals, based upon molecular structures that consist of combined siloxane and mesogenic moieties, exhibit strong multiple scattering of light with and without the presence of an electric field. This paper demonstrates that when one adds a laser dye to these compounds it is possible to observe random laser emission under optical excitation, and that the output can be varied depending upon the scattering state that is induced by the electric field. Results are presented to show that the excitation threshold of a dynamic scattering state, consisting of chaotic motion due to electro-hydrodynamic instabilities, exhibits lower lasing excitation thresholds than the scattering states that exist in the absence of an applied electric field. However, the lowest threshold is observed for a dynamic scattering state that does not have the largest scattering strength but which occurs when there is optimization of the combined light absorption and scattering properties.

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Random lasing in ZnO nanocrystals

Cited by 48 publications

References 12 publications

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

Random lasing in nanocrystalline ZnO powders

Lowering the excitation threshold of a random laser using the dynamic scattering states of an organosiloxane smectic A liquid crystal

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