Recombination dynamics of deep defect states in zinc oxide nanowires

Lettieri, S.; Amato, Luigi Santamaria; Maddalena, P.; Comini, Elisabetta; Baratto, C.; Todros, Silvia

doi:10.1088/0957-4484/20/17/175706

Cited by 37 publications

(22 citation statements)

References 28 publications

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“…Luminescence output was integrated over the thickness of the crystal by taking into account reabsorption [5]. The obtained values of exciton bimolecular recombination coefficient b r = 10 -10 cm 3 s -1 and diffusion coefficient D = 3 cm 2 /s are in line with the published values for ZnO [2,6,10]. Similar luminescence decay profiles were observed for other highly 1P excited ZnO samples.…”

supporting

confidence: 85%

Luminescence of ZnO crystals under surface and bulk excitation regimes

Serevičius

Miasojedovas

Gavryushin

et al. 2009

Phys. Status Solidi (c)

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Luminescence properties of vapor phase grown ZnO single crystals with different content of deep traps were explored under one‐photon and two‐photon excitation. Room‐temperature near bandgap emission of highly excited ZnO crystals was originated by inelastic exciton scattering. Under surface excitation regime, luminescence decay profile was governed by exciton diffusion and bimolecular recombination. At higher excitation, exciton recombination transients were significantly altered by stimulated emission. Two‐photon bulk‐like excitation revealed exciton recombination dynamics related to defect states. Correlation between the luminescence decay rate and the density of deep trap states of variously annealed crystals was observed. Results on crystal optical quality were in line with estimated values of stimulated emission threshold. The largest value of the average luminescence decay time τlu = 1.5 ns and the lowest value of the stimulated emission threshold Iexc = 0.6 mJ/cm2 were obtained for ZnO crystal annealed in vacuum. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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supporting

confidence: 85%

Luminescence of ZnO crystals under surface and bulk excitation regimes

Serevičius

Miasojedovas

Gavryushin

et al. 2009

Phys. Status Solidi (c)

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“…III A., the cores of the highly crystalline particles dictate the CL emission, thus the coefficient value for bulk ZnO was used instead of those for ZnO nanostructures. 37 Assuming a shallow donor concentration of N D present in ZnO, the neutrality condition must be satisfied n + n T = p + N D .…”

Section: B Dependence Of Gl Intensities On CL Excitation Powermentioning

confidence: 99%

Characteristics of point defects in the green luminescence from Zn- and O-rich ZnO

2012

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Cathodoluminescence spectra have been measured to determine the characteristics of ubiquitous green luminescence (GL) in nonstoichiometric zinc oxide (ZnO). Zn-and O-rich ZnO were found to exhibit characteristic emissions at 2.53 eV [full width at half-maximum (FWHM) 340 meV] and 2.30 eV (FWHM 450 meV), respectively. Hydrogen was used to probe the physical nature of GL centers. The Zn-rich GL is enhanced upon H incorporation, whereas the O-rich GL is completely quenched as its underlying acceptor-like V Zn centers are passivated by H. The GL emission bands each exhibit remarkably different excitation-power dependencies. The Zn-rich GL follows a close to linear relationship with excitation power, while the O-rich GL exhibits a square-root dependence. Calculations based on bimolecular recombination equations show the defect concentration in Zn-rich ZnO is three orders of magnitude greater than that in O-rich ZnO, indicating V O is more readily formed than V Zn in thermochemical treatments of ZnO.

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“…[13][14][15][16][17][18][19][20][21][22][23] Unfortunately, approaches based on intensity measurement of the PL emission are also prone to errors. In particular, fluctuations in the excitation light intensity can hinder the understanding of the experimental data when real-time monitoring is performed and small integration times in the PL measurement have to be used.…”

mentioning

confidence: 99%

Unconventional ratiometric-enhanced optical sensing of oxygen by mixed-phase TiO2

Lettieri

Pallotti

Gesuele

et al. 2016

Applied Physics Letters

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Abstract. We show that mixed-phase titanium dioxide (TiO2) can be effectively employed as an unconventional, inorganic, dual-emitting and ratiometric optical sensor of O2. Simultaneous availability of rutile and anatase TiO2 PL and their peculiar "anti-correlated" PL responses to O2 allow using their ratio as measurement parameter associated to O2 concentration, leading to an experimental responsivity being by construction larger than the one obtainable for single-phase PL detection. A proof of this concept in given, showing a two-fold enhancement of the optical responsivity provided by the ratiometric approach. Besides the peculiar ratiometric-enhanced responsivity, other characteristics of mixed phase TiO2 can be envisaged as favorable for O2 optical probing, namely: a) low production costs, b) absence of heterogeneous components, c) self-supporting properties. These characteristics encourage experimenting its use for applications requiring high indicator quantities at competitive price, possibly also tackling the need to develop supporting matrixes that carry the luminescent probes and avoiding issues related to the use of different components for ratiometric sensing.Determining the content of molecular oxygen (O2) in gas mixtures and/or aqueous environments is important in many different fields. For example, monitoring the O2 concentration in the exhaust stream of an internal combustion engine provides information on the air-fuel ratio of the combustion process, whose control is relevant for reducing harmful emission [1][2][3] . Knowing the concentration of O2 dissolved in water (also "dissolved oxygen", DO) is also crucial in many applications. DO level is intimately related to the state of health of marine habitats, to the concentration of organic pollutants in water 4 and is of great importance for biological studies. In fact, DO content in cell culture media affects cell growth rate, metabolism and protein synthesis, exerting a decisive influence on the cellular functions and behaviors. To mention a few examples, hypoxia/re-oxygenation induce stem cell like

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Recombination dynamics of deep defect states in zinc oxide nanowires

Cited by 37 publications

References 28 publications

Luminescence of ZnO crystals under surface and bulk excitation regimes

Luminescence of ZnO crystals under surface and bulk excitation regimes

Characteristics of point defects in the green luminescence from Zn- and O-rich ZnO

Unconventional ratiometric-enhanced optical sensing of oxygen by mixed-phase TiO2

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