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Photoluminescence of spray pyrolysis deposited ZnO nanorods.

Kärber E, Raadik T, Dedova T, Krustok J, Mere A, Mikli V, Krunks M - Nanoscale Res Lett (2011)

Bottom Line: A dominant near band edge (NBE) emission is observed at 300 K and at 10 K.High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions.It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia. malle@staff.ttu.ee.

ABSTRACT
Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km.

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Excitonic photoluminescence spectra at 10 K of ZnO nanorod layers deposited at different growth temperatures. The growth temperature is kept at 480°C, 530°C, or 550°C, illustrated by spectrum A, B, and C, respectively. The ZnO nanorod layers are deposited onto ITO/SGL substrates from aqueous solution at similar spray rate (2.2 ml/min). Spectrum C is shown with fitting results, Raman spectrum of the corresponding ZnO nanorod sample is presented in Figure 1 and the SEM image is presented in Figure 3a. The SEM image of the sample corresponding to spectrum A is presented in Figure 3b.
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Figure 5: Excitonic photoluminescence spectra at 10 K of ZnO nanorod layers deposited at different growth temperatures. The growth temperature is kept at 480°C, 530°C, or 550°C, illustrated by spectrum A, B, and C, respectively. The ZnO nanorod layers are deposited onto ITO/SGL substrates from aqueous solution at similar spray rate (2.2 ml/min). Spectrum C is shown with fitting results, Raman spectrum of the corresponding ZnO nanorod sample is presented in Figure 1 and the SEM image is presented in Figure 3a. The SEM image of the sample corresponding to spectrum A is presented in Figure 3b.

Mentions: From our previous study, it is known that the increase of TG from 480°C up to 550°C minimizes the intensity of the green PL band at 300 K [25]. The spectra recorded at T = 10 K (Figure 5) reveal that an increase of TG from 480°C up to 550°C results in a PL spectra with significantly increased excitonic intensity, showing FWHM of 4.5 meV for ZnONRL grown at TG = 550°C onto ITO/SGL substrate. Such low values of FWHM (4.5 meV) can be correlated to a very low concentration of defects [42]. In addition, the increase of the growth temperature of ZnONRL results in an increase of the ratio of NBE to red band intensity (the red band is not shown in Figure 5). The INBE/IRED emission ratio increases as follows: 34, 39, and 160, illustrated by spectrum A, B, and C (in Figure 5), respectively. This is an indication of significant change in the defect composition in the ZnONRL and an increase of the crystal quality due to an increase of the growth temperature of ZnONRL. According to SEM study, the characteristic morphology of the samples changes with different TG. The SEM image in Figure 3a is a characteristic of ZnONRL grown at TG = 550°C. A significantly lower surface-to-volume area (no quantitative calculations were made) could be estimated from Figure 3b, presenting the SEM image of ZnONRL deposited at TG = 480°C. At the same time, an increase of the excitonic PL band was registered without a decrease of the FWHM of the fitted peaks (Figure 5, spectra A-C). Therefore, the increase of the intensity of the excitonic band could be due to a higher surface-to-volume ratio of the ZnONRL, in addition to an increased crystal quality. A similar effect was described for the electrochemically synthesized ZnO nanowires [20].


Photoluminescence of spray pyrolysis deposited ZnO nanorods.

Kärber E, Raadik T, Dedova T, Krustok J, Mere A, Mikli V, Krunks M - Nanoscale Res Lett (2011)

Excitonic photoluminescence spectra at 10 K of ZnO nanorod layers deposited at different growth temperatures. The growth temperature is kept at 480°C, 530°C, or 550°C, illustrated by spectrum A, B, and C, respectively. The ZnO nanorod layers are deposited onto ITO/SGL substrates from aqueous solution at similar spray rate (2.2 ml/min). Spectrum C is shown with fitting results, Raman spectrum of the corresponding ZnO nanorod sample is presented in Figure 1 and the SEM image is presented in Figure 3a. The SEM image of the sample corresponding to spectrum A is presented in Figure 3b.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211449&req=5

Figure 5: Excitonic photoluminescence spectra at 10 K of ZnO nanorod layers deposited at different growth temperatures. The growth temperature is kept at 480°C, 530°C, or 550°C, illustrated by spectrum A, B, and C, respectively. The ZnO nanorod layers are deposited onto ITO/SGL substrates from aqueous solution at similar spray rate (2.2 ml/min). Spectrum C is shown with fitting results, Raman spectrum of the corresponding ZnO nanorod sample is presented in Figure 1 and the SEM image is presented in Figure 3a. The SEM image of the sample corresponding to spectrum A is presented in Figure 3b.
Mentions: From our previous study, it is known that the increase of TG from 480°C up to 550°C minimizes the intensity of the green PL band at 300 K [25]. The spectra recorded at T = 10 K (Figure 5) reveal that an increase of TG from 480°C up to 550°C results in a PL spectra with significantly increased excitonic intensity, showing FWHM of 4.5 meV for ZnONRL grown at TG = 550°C onto ITO/SGL substrate. Such low values of FWHM (4.5 meV) can be correlated to a very low concentration of defects [42]. In addition, the increase of the growth temperature of ZnONRL results in an increase of the ratio of NBE to red band intensity (the red band is not shown in Figure 5). The INBE/IRED emission ratio increases as follows: 34, 39, and 160, illustrated by spectrum A, B, and C (in Figure 5), respectively. This is an indication of significant change in the defect composition in the ZnONRL and an increase of the crystal quality due to an increase of the growth temperature of ZnONRL. According to SEM study, the characteristic morphology of the samples changes with different TG. The SEM image in Figure 3a is a characteristic of ZnONRL grown at TG = 550°C. A significantly lower surface-to-volume area (no quantitative calculations were made) could be estimated from Figure 3b, presenting the SEM image of ZnONRL deposited at TG = 480°C. At the same time, an increase of the excitonic PL band was registered without a decrease of the FWHM of the fitted peaks (Figure 5, spectra A-C). Therefore, the increase of the intensity of the excitonic band could be due to a higher surface-to-volume ratio of the ZnONRL, in addition to an increased crystal quality. A similar effect was described for the electrochemically synthesized ZnO nanowires [20].

Bottom Line: A dominant near band edge (NBE) emission is observed at 300 K and at 10 K.High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions.It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia. malle@staff.ttu.ee.

ABSTRACT
Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km.

No MeSH data available.


Related in: MedlinePlus