Optical Properties of ZnO

Reynolds, D. C.; Litton, C. W.; Collins, T. C.

doi:10.1002/9781119991038.ch2

Cited by 4 publications

(3 citation statements)

References 65 publications

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“…However, this picture is not reliable since radiative carrier recombination is dominated by minority carrier (hole) distribution. Our estimation suggests that an uncompensated piezoelectric field at the ZnO NR apex (7.53 × 10 8 V/cm) can be significantly larger than what is needed to dissociate ZnO FX with a Bohr radius of a B = 1.35 nm (4.4 × 10 5 V/cm). However, such an electric field higher than the typical bulk ZnO breakdown field (2 × 10 6 V/cm) is not maintained, and more realistically the piezoelectric charges should be compensated by residual carriers (Supplementary Note 4).…”

Section: Resultsmentioning

confidence: 87%

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Band-Gap Deformation Potential and Elasticity Limit of Semiconductor Free-Standing Nanorods Characterized in Situ by Scanning Electron Microscope–Cathodoluminescence Nanospectroscopy

et al. 2015

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Modern field-effect transistors or laser diodes take advantages of band-edge structures engineered by large uniaxial strain εzz, available up to an elasticity limit at a rate of band-gap deformation potential azz (= dEg/dεzz). However, contrary to aP values under hydrostatic pressure, there is no quantitative consensus on azz values under uniaxial tensile, compressive, and bending stress. This makes band-edge engineering inefficient. Here we propose SEM-cathodoluminescence nanospectroscopy under in situ nanomanipulation (Nanoprobe-CL). An apex of a c-axis-oriented free-standing ZnO nanorod (NR) is deflected by point-loading of bending stress, where local uniaxial strain (εcc = r/R) and its gradient across a NR (dεcc/dr = R(-1)) are controlled by a NR local curvature (R(-1)). The NR elasticity limit is evaluated sequentially (εcc = 0.04) from SEM observation of a NR bending deformation cycle. An electron beam is focused on several spots crossing a bent NR, and at each spot the local Eg is evaluated from near-band-edge CL emission energy. Uniaxial acc (= dEg/dεcc) is evaluated at regulated surface depth, and the impact of R(-1) on observed acc is investigated. The acc converges with -1.7 eV to the R(-1) = 0 limit, whereas it quenches with increasing R(-1), which is attributed to free-exciton drift under transversal band-gap gradient. Surface-sensitive CL measurements suggest that a discrepancy from bulk acc = -4 eV may originate from strain relaxation at the side surface under uniaxial stress. The nanoprobe-CL technique reveals an Eg(εij) response to specific strain tensor εij (i, j = x, y, z) and strain-gradient effects on a minority carrier population, enabling simulations and strain-dependent measurements of nanodevices with various structures.

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Section: Resultsmentioning

confidence: 87%

“…The statistical E FX 0 difference does not affect the accuracy of the obtained a cc N , the first derivative of δ E g . Any effect by quantum confinement energy is ignored since the FX Bohr radius ( a B = 1.35 nm) is much smaller than the NR diameter ( D = 150 nm).…”

Section: Methodsmentioning

confidence: 99%

Band-Gap Deformation Potential and Elasticity Limit of Semiconductor Free-Standing Nanorods Characterized in Situ by Scanning Electron Microscope–Cathodoluminescence Nanospectroscopy

et al. 2015

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“…Figure 5(c) indicates that heated albumen-covered ZnO NRs increase NBE emission intensity while decreasing DL emission intensity. A high NBE to DL emission ratio indicates that the semiconductor material has a high degree of crystallinity and indicates that there are fewer deep-level defects in the semiconductor material [55,56]. Also, it confirms that the majority of the photons emitted are from the near band-edge of the semiconductor material.…”

Section: Optical Properties Of the Zno Nrsmentioning

confidence: 84%

The effects of nontoxic bio-based substances (egg white) on the performance and passivation of ZnO nanorods arrays-based light emitting devices

Chuang,

Feria,

et al. 2024

Nanotechnology

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An innovative approach is proposed to passivate the existing defects from metal oxide semiconductors by functionalizing nontoxic bio-based substances. As a demonstration, we synthesized zinc oxide nanorods (ZnO NRs) using a hydrothermal method and incorporated chicken egg white (albumen) as a passivator to the defects. XRD analysis of ZnO NRs shows enhanced quality and crystallinity features after incorporating albumen. XPS measurements were performed not only to introduce the chemical bonding between the albumen and the bare ZnO NRs but also specifically provide evidence of successful capping and defect passivation to the surface layer of ZnO NRs. It was observed that when the albumen was annealed, it formed sulfhydryl groups and disulfide bonds (which created disulfide bridges) from the chemical reaction in irreversible thermal denaturation. Steady-state photoluminescence of ZnO NRs showed two emission bands, i.e., near band-edge emission (NBE) and deep-level emission (DL). The NBE is significantly improved as compared to DL emission after capping and annealing the albumen, while the quenching of DL emission confirmed the reduced defects arising from the surface of ZnO NRs. The advantages and enhanced characteristics of the albumen-capped ZnO NRs led to fabricating a stable and highly efficient light-emitting device. This work opens the great potential of utilizing nontoxic and low-cost biomaterials in passivating the defects of metal oxide nanomaterials for the development of bio-inspired and stable optoelectronic devices.

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Synthesis and optical properties of undoped and Eu-doped ZnS nanoparticles

Ashwini¹,

Pandurangappa²,

Nagabhushana

2012

Phys. Scr.

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Pure and europium (Eu)-doped zinc sulfide (ZnS) nanoparticles were synthesized by the solvothermal method and characterized by powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and photoluminescence (PL). The XRD pattern showed that as-prepared samples are a mixture of complex chemical groups. Heat treatment of the samples at 300 °C showed a phase transformation of the complex chemical mixture to the ZnS state. The crystallite size of undoped ZnS was found to be ∼23 nm. However, ZnS:Eu nanoparticles showed a crystallite size of ∼28 nm. The lattice constant of undoped ZnS was found to be 5.382 Å and that of Eu-doped ZnS was 5.34 Å. Further heating the samples to 500 °C showed a phase transition to the ZnO state. The SEM studies revealed that ZnS nanoparticles are agglomerated, crispy and porous. The FTIR spectrum showed the presence of hydroxyl groups in the sample. The PL studies showed a shift in the emission peak from 390 to 420 nm upon heating the samples from 300 to 500 °C.

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Optical Properties of ZnO

Cited by 4 publications

References 65 publications

Band-Gap Deformation Potential and Elasticity Limit of Semiconductor Free-Standing Nanorods Characterized in Situ by Scanning Electron Microscope–Cathodoluminescence Nanospectroscopy

Band-Gap Deformation Potential and Elasticity Limit of Semiconductor Free-Standing Nanorods Characterized in Situ by Scanning Electron Microscope–Cathodoluminescence Nanospectroscopy

The effects of nontoxic bio-based substances (egg white) on the performance and passivation of ZnO nanorods arrays-based light emitting devices

Synthesis and optical properties of undoped and Eu-doped ZnS nanoparticles

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