Temperature dependence of bulk luminescence from ZnO

Cui, Miao; Zhang, Zili; Wang, Yafang; Finch, Adrian A.; Townsend, Peter

doi:10.1002/bio.3460

Cited by 10 publications

(4 citation statements)

References 34 publications

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“…Since the point defects concentration is enhanced, reducing the dimensions, this result confirms that the intensity of the exciton luminescence is strongly affected by the presence of defect states. Furthermore, the excitonic emission, almost resonant with the ZnO band gap, can be reabsorbed by the sample [ 66 , 67 ], thus increasing the probability of interaction between the excitation and the defects. Our suggested interpretation is that, in nano-systems, the probability that the excitations transfer their energy non-radiatively to emissive defects or quenching centers—rather than undergoing radiative relaxation—is higher than in micrometric and bulk samples, which typically are affected by a lower degree of defectiveness.…”

Section: Discussionmentioning

confidence: 99%

Morphology Related Defectiveness in ZnO Luminescence: From Bulk to Nano-Size

et al. 2020

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This study addresses the relationship between material morphology (size, growth parameters and interfaces) and optical emissions in ZnO through an experimental approach, including the effect of different material dimensions from bulk to nano-size, and different excitations, from optical sources to ionizing radiation. Silica supported ZnO nanoparticles and ligand capped ZnO nanoparticles are synthesized through a sol–gel process and hot injection method, respectively. Their optical properties are investigated by radioluminescence, steady-state and time-resolved photoluminescence, and compared to those of commercial micrometric powders and of a bulk single crystal. The Gaussian spectral reconstruction of all emission spectra highlights the occurrence of the same emission bands for all samples, comprising one ultraviolet excitonic peak and four visible defect-related components, whose relative intensities and time dynamics vary with the material parameters and the measurement conditions. The results demonstrate that a wide range of color outputs can be obtained by tuning synthesis conditions and size of pure ZnO nanoparticles, with favorable consequences for the engineering of optical devices based on this material.

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Section: Discussionmentioning

confidence: 99%

Morphology Related Defectiveness in ZnO Luminescence: From Bulk to Nano-Size

et al. 2020

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“…Each CL spectrum was fitted to a linear superposition of the NBE, S, DE1, and DE2 peaks, where the energy and width of the distributions were fixed according to fits from the CL (NBE and S) and PL (DE1 and DE2) spectra 41 (see Figures SI2 and SI3 and Table 1). Although room-temperature PL is used to fit defect peaks, the temperature dependence of the peak positions is expected to be weak; recent measurements of defect emission have shown only small shifts (∼0.1 eV) between 300 and 100 K. 42 This deconvolution routine accurately accounts for the full hyperspectral CL image (Figure SI5) and allows amplitude maps of each component to be plotted (Figure 3b−e). The errors in the peak amplitudes from the deconvolution routine are mapped in Figure SI6.…”

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confidence: 99%

Mapping the Origins of Luminescence in ZnO Nanowires by STEM-CL

Kennedy

White

Howkins

et al. 2019

J. Phys. Chem. Lett.

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In semiconductor nanowires, understanding both the sources of luminescence (excitonic recombination, defects, etc.) and the distribution of luminescent centers (be they uniformly distributed, or concentrated at structural defects or at the surface) is important for synthesis and applications. We develop scanning transmission electron microscopy−cathodoluminescence (STEM-CL) measurements, allowing the structure and cathodoluminescence (CL) of single ZnO nanowires to be mapped at high resolution. Using a CL pixel resolution of 10 nm, variations of the CL spectra within such nanowires in the direction perpendicular to the nanowire growth axis are identified for the first time. By comparing the local CL spectra with the bulk photoluminescence spectra, the CL spectral features are assigned to internal and surface defect structures. Hyperspectral CL maps are deconvolved to enable characteristic spectral features to be spatially correlated with structural features within single nanowires. We have used these maps to show that the spatial distribution of these defects correlates well with regions that show an increased rate of nonradiative transitions.

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“…Even the excitation wavelength is comparable with the bandgap of the ZnO but different intensity from different orientation points that the emission sites concentration varies as we change the orientation. The presence of high NBE emission in <0001> face with weak emission in DLE region states that, in <0001> the electron-hole recombination is dominant and the vacancies level is lower in this orientation as we know that the deep level emission is mainly attributed to various intrinsic defects as shown in Figure 6 (such as VZn, VO, Zni, and Oi) [34][35][36]. Generally, in intrinsic ZnO, Vo and Zni are two notable defects that act as deep and shallow defects, respectively [37].…”

Section: Room-temperature and Low-temperature Photoluminescence Spect...mentioning

confidence: 97%

Orientation-Mediated Luminescence Enhancement and Spin-Orbit Coupling in ZnO Single Crystals

et al. 2022

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Temperature-, excitation wavelength-, and excitation power-dependent photoluminescence (PL) spectroscopy have been utilized to investigate the orientation-modulated near band edge emission (NBE) and deep level emission (DLE) of ZnO single crystals (SCs). The near-band-edge emission of ZnO SC with <0001> orientation exhibits strong and sharp emission intensity with suppressed deep level defects (mostly caused by oxygen vacancies Vo). Furthermore, Raman analysis reveals that <0001> orientation has dominant E2 (high) and E2 (low) modes, indicating that this direction has better crystallinity. At low temperature, the neutral donor-to-bound exciton (DoX) transition dominates, regardless of the orientation, according to the temperature-dependent PL spectra. Moreover, free-exciton (FX) transition emerges at higher temperatures in all orientations. The PL intensity dependence on the excitation power has been described in terms of power-law (I~Lα). Our results demonstrate that the α for <0001>, <1120>, and <1010> is (1.148), (1.180), and (1.184) respectively. In short, the comprehensive PL analysis suggests that DoX transitions are dominant in the NBE region, whereas oxygen vacancies (Vo) are the dominant deep levels in ZnO. In addition, the <0001> orientation contains fewer Vo-related defects with intense excitonic emission in the near band edge region than other counterparts, even at high temperature (~543 K). These results indicate that <0001> growth direction is favorable for fabricating ZnO-based highly efficient optoelectronic devices.

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Temperature dependence of bulk luminescence from ZnO

Cited by 10 publications

References 34 publications

Morphology Related Defectiveness in ZnO Luminescence: From Bulk to Nano-Size

Morphology Related Defectiveness in ZnO Luminescence: From Bulk to Nano-Size

Mapping the Origins of Luminescence in ZnO Nanowires by STEM-CL

Orientation-Mediated Luminescence Enhancement and Spin-Orbit Coupling in ZnO Single Crystals

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