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Enhancement of electroluminescence from embedded Si quantum dots/SiO2multilayers film by localized-surface-plasmon and surface roughening.

Li W, Wang S, Hu M, He S, Ge P, Wang J, Guo YY, Zhaowei L - Sci Rep (2015)

Bottom Line: The result shows that electroluminescence intensity was significantly enhanced.And, the turn-on voltage of the luminescent device was reduced to 3 V.The other factors were the improved absorption of excitation light and the increase of light extraction ratio by surface roughening structures.

View Article: PubMed Central - PubMed

Affiliation: 1] College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing, 210003 China [2] Key Laboratory of Radio Frequency and Micro-Nano Electronics of Jiangsu Province, Nanjing 210023, Jiangsu, China [3] Department of Electrical and Computer Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0407, USA.

ABSTRACT
In this paper, we prepared a novel structure to enhance the electroluminescence intensity from Si quantum dots/SiO2multilayers. An amorphous Si/SiO2 multilayer film was fabricated by plasma-enhanced chemical vapor deposition on a Pt nanoparticle (NP)-coated Si nanopillar array substrate. By thermal annealing, an embedded Si quantum dot (QDs)/SiO2 multilayer film was obtained. The result shows that electroluminescence intensity was significantly enhanced. And, the turn-on voltage of the luminescent device was reduced to 3 V. The enhancement of the light emission is due to the resonance coupling between the localized-surface-plasmon (LSP) of Pt NPs and the band-gap emission of Si QDs/SiO2 multilayers. The other factors were the improved absorption of excitation light and the increase of light extraction ratio by surface roughening structures. These excellent characteristics are promising for silicon-based light-emitting applications.

No MeSH data available.


The curves of ln(I/V2) and 1/V for the samples with pillar.The inset is the curves for the sample without pillar.
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f5: The curves of ln(I/V2) and 1/V for the samples with pillar.The inset is the curves for the sample without pillar.

Mentions: Figure 3(a) and Fig. 3(b) show the EL spectra of a Si QDs/SiO2 multilayer film deposited on substrate without and with the Pt NP-coated nanopillar array. The EL signals were collected when applying DC voltage (from 3 V to15 V) and it shows that the EL band is quite broad. It looks like that the EL spectra of the sample without Si nanopillar contains at least two sub-bands located at 520 nm and 650 nm, respectively due to the different luminescence routes22232425.This spectra is from QCE in Si nanocrystals and defect-related EL bands in SiO2-based nanostructures. And these two bands also appear in the EL spectra of the sample with Si nanopillar. As observed from Fig. 3, the EL intensity increases with increased voltage. And the most important is that the EL intensity is obviously enhanced for the sample with Pt NPs-coated Si nanopillar compared to that without Pt NPs-coated Si nanopillar. Figure 4a depicts the normalized integrated EL intensities IEL of the samples with and without Pt NPs-coated Si nanopillar as a function of applied voltage. The IEL of both samples increases with increased voltage. When the applied voltage is 8 V or 10 V, the integrated EL intensities of the sample with Pt NPs-coated Si nanopillars are about 10 times stronger than that of without Pt NPs-coated Si nanopillars. Figure 4b shows the ratio of integrated EL intensity to the injection current as a function of applied voltage for both samples. The ratio of integrated EL intensity to the injection current directly reflects the external quantum efficiency. It is clearly shown that the external quantum efficiency is obviously enhanced for samples with Si pillar. The EL efficiency can be improved by almost two orders of magnitude as shown in Fig. 4(b). It was reported that the EL intensity can be improved due to the enhanced Fowler-Nordheim (F-N) tunneling process by introducing Si interfacial nano-pyramids26. The plots of ln (I/V2) vs 1/V for both samples are shown in Fig. 5. A nearly linear behavior for the samples with Si nanopillar indicates that the EL follows F-N tunneling mechanism in our case. Meanwile, it is found that the threshold voltage to initiate F-N tunneling is reduced obviously.The enhancement of the light emission is due to the resonance coupling between the LSP of Pt NPs. When the light emission wavelength of Si QDs/SiO2 multilayer is close to the extinction peak of Pt nanoparticles, this coupling process occurs. It is reported that the LSP energy of Pt NPs can be tuned in a wide range from the deep-UV to visible region by size control2728. Figure 6 shows the extinction spectra of Pt nanoparticles. As expected, there is a wide extinction peak in this spectra. And, the FWHM of the peak is around 200 nm. In our researches, the Pt nanoparticle size is in the range of about 40 nm to 80 nm, shown in Fig. 1(b). This is the reason of the wide FWHM. Langhammer has reported that Pt nanoparticles have broader resonance peak and larger nonradiative damping than Au2930. In our case, the peak of EL spectra from Si QDs is also wide (Fig. 3a). So, the LSP energy of Pt nanoparticle is close to the band-gap emission of the sample. Meanwhile, the larger nanoradiative damping make the more energy transfer from Pt nanoparticles to Si QDs. In addition, the better contract between Pt nanoparticles and Si QDs/SiO2 multilayer is formed after annealing. It is helpful for the LSP coupling.


Enhancement of electroluminescence from embedded Si quantum dots/SiO2multilayers film by localized-surface-plasmon and surface roughening.

Li W, Wang S, Hu M, He S, Ge P, Wang J, Guo YY, Zhaowei L - Sci Rep (2015)

The curves of ln(I/V2) and 1/V for the samples with pillar.The inset is the curves for the sample without pillar.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490393&req=5

f5: The curves of ln(I/V2) and 1/V for the samples with pillar.The inset is the curves for the sample without pillar.
Mentions: Figure 3(a) and Fig. 3(b) show the EL spectra of a Si QDs/SiO2 multilayer film deposited on substrate without and with the Pt NP-coated nanopillar array. The EL signals were collected when applying DC voltage (from 3 V to15 V) and it shows that the EL band is quite broad. It looks like that the EL spectra of the sample without Si nanopillar contains at least two sub-bands located at 520 nm and 650 nm, respectively due to the different luminescence routes22232425.This spectra is from QCE in Si nanocrystals and defect-related EL bands in SiO2-based nanostructures. And these two bands also appear in the EL spectra of the sample with Si nanopillar. As observed from Fig. 3, the EL intensity increases with increased voltage. And the most important is that the EL intensity is obviously enhanced for the sample with Pt NPs-coated Si nanopillar compared to that without Pt NPs-coated Si nanopillar. Figure 4a depicts the normalized integrated EL intensities IEL of the samples with and without Pt NPs-coated Si nanopillar as a function of applied voltage. The IEL of both samples increases with increased voltage. When the applied voltage is 8 V or 10 V, the integrated EL intensities of the sample with Pt NPs-coated Si nanopillars are about 10 times stronger than that of without Pt NPs-coated Si nanopillars. Figure 4b shows the ratio of integrated EL intensity to the injection current as a function of applied voltage for both samples. The ratio of integrated EL intensity to the injection current directly reflects the external quantum efficiency. It is clearly shown that the external quantum efficiency is obviously enhanced for samples with Si pillar. The EL efficiency can be improved by almost two orders of magnitude as shown in Fig. 4(b). It was reported that the EL intensity can be improved due to the enhanced Fowler-Nordheim (F-N) tunneling process by introducing Si interfacial nano-pyramids26. The plots of ln (I/V2) vs 1/V for both samples are shown in Fig. 5. A nearly linear behavior for the samples with Si nanopillar indicates that the EL follows F-N tunneling mechanism in our case. Meanwile, it is found that the threshold voltage to initiate F-N tunneling is reduced obviously.The enhancement of the light emission is due to the resonance coupling between the LSP of Pt NPs. When the light emission wavelength of Si QDs/SiO2 multilayer is close to the extinction peak of Pt nanoparticles, this coupling process occurs. It is reported that the LSP energy of Pt NPs can be tuned in a wide range from the deep-UV to visible region by size control2728. Figure 6 shows the extinction spectra of Pt nanoparticles. As expected, there is a wide extinction peak in this spectra. And, the FWHM of the peak is around 200 nm. In our researches, the Pt nanoparticle size is in the range of about 40 nm to 80 nm, shown in Fig. 1(b). This is the reason of the wide FWHM. Langhammer has reported that Pt nanoparticles have broader resonance peak and larger nonradiative damping than Au2930. In our case, the peak of EL spectra from Si QDs is also wide (Fig. 3a). So, the LSP energy of Pt nanoparticle is close to the band-gap emission of the sample. Meanwhile, the larger nanoradiative damping make the more energy transfer from Pt nanoparticles to Si QDs. In addition, the better contract between Pt nanoparticles and Si QDs/SiO2 multilayer is formed after annealing. It is helpful for the LSP coupling.

Bottom Line: The result shows that electroluminescence intensity was significantly enhanced.And, the turn-on voltage of the luminescent device was reduced to 3 V.The other factors were the improved absorption of excitation light and the increase of light extraction ratio by surface roughening structures.

View Article: PubMed Central - PubMed

Affiliation: 1] College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing, 210003 China [2] Key Laboratory of Radio Frequency and Micro-Nano Electronics of Jiangsu Province, Nanjing 210023, Jiangsu, China [3] Department of Electrical and Computer Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0407, USA.

ABSTRACT
In this paper, we prepared a novel structure to enhance the electroluminescence intensity from Si quantum dots/SiO2multilayers. An amorphous Si/SiO2 multilayer film was fabricated by plasma-enhanced chemical vapor deposition on a Pt nanoparticle (NP)-coated Si nanopillar array substrate. By thermal annealing, an embedded Si quantum dot (QDs)/SiO2 multilayer film was obtained. The result shows that electroluminescence intensity was significantly enhanced. And, the turn-on voltage of the luminescent device was reduced to 3 V. The enhancement of the light emission is due to the resonance coupling between the localized-surface-plasmon (LSP) of Pt NPs and the band-gap emission of Si QDs/SiO2 multilayers. The other factors were the improved absorption of excitation light and the increase of light extraction ratio by surface roughening structures. These excellent characteristics are promising for silicon-based light-emitting applications.

No MeSH data available.