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Localized excitons mediate defect emission in ZnO powders
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Image of FIG. 1.
FIG. 1.

(a) PL spectra of ZnO:Zn at different temperatures showing both the UV band edge and green defect emission when excited by the Xe lamp at 350 nm. (b) Temperature dependence of integrated UV and peak green emission overlaid by the corresponding Arrhenius fit.

Image of FIG. 2.
FIG. 2.

(a) UV PL spectra, (b) UV PLE spectra, and (c) green PLE spectra of ZnO:Zn at various temperatures. The vertical dotted line under I 9 (green online) suggests common origin of three peaks. The PL spectra were obtained by exciting the sample with the Xe lamp at 350 nm.

Image of FIG. 3.
FIG. 3.

Schematic energy diagram illustrating the relevant photoionization and thermal delocalization pathways for the proposed bound excitonic processes. (Exciton: blue oval. Donor: red circle.)

Image of FIG. 4.
FIG. 4.

(a) Intensity of the green emission at each excitation energy as a function of temperature. (b) Activation energies associated with the green emission as a function of excitation energy Eexc above the T = 0 band gap energy Eg .

Image of FIG. 5.
FIG. 5.

(a) PL intensity, (b) external quantum efficiencies ηUV and ηGR , and (c) the ratio PL/η of the UV and green emissions plotted as a function of cw pump intensity for the HeCd laser operating at 325 nm.

Image of FIG. 6.
FIG. 6.

Comparison of the UV and green PLE spectra with the quantum efficiency spectrum for green emission at room temperature.


Generic image for table
Table I.

Best-fit parameters for PL thermal quenching of UV and green emission bands.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Localized excitons mediate defect emission in ZnO powders