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Origin and spectral degradation of the photoluminescence from a-SiOx
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View: Figures


Image of FIG. 1.
FIG. 1.

PL spectra of a-SiO with 39 at. % < [Si] < 59 at. %. (a) The initial spectra shift to the blue spectral range with decreasing Si content. (b) After degradation, the emission maxima coincide at  = 2.16 eV for [Si] < 47 at. %. The spectrum of the sample with [Si] = 59 at. % is not affected by the degradation.

Image of FIG. 2.
FIG. 2.

Summary of emission maxima of both initial and degraded PL-spectra. The spectral degradation restricts the emission maxima to  < 2.16 eV. The emission maxima of samples with  < 2.16 eV are not affected by the spectral degradation. Most other publications did not report on luminescence of a-SiO above  = 2.16 eV. 3,13,23 Probably, spectral degradation for these samples already occurred before the PL measurements.

Image of FIG. 3.
FIG. 3.

Measured initial (solid curves) and modeled (dotted curves) PL spectra. The modeled spectra calculate from and according to the band tail luminescence model (Eq. (1) ). Both measured and modeled spectra agree well in and the spectral shape. The overestimation of the low energetic and the underestimation of the high energetic shoulder are in accordance with the explanatory approach.

Image of FIG. 4.
FIG. 4.

The measured and modeled initial PL spectra differ in shape. The overestimation of the low energetic ΔΦ shoulder arises from (a) non-radiative recombination via defect states. The underestimation on the high energetic ΔΦ side results from (b) the excitation of defect states and (c) the contribution of change carriers excited above the conduction band edge.

Image of FIG. 5.
FIG. 5.

Initial (dashed curves) and degraded (solid curves) PL spectra replotted from Figures 1(a) and 1(b) . (a) For samples with  > 2.16 eV, the degradation causes a redshift by Δ . The degraded spectra share a common maximum around  ≈ 2.16 eV. The sample with [Si] = 47 at. % remains unchanged since  ≈   ≈ 2.16 eV. (b) In the spectra of samples with  < 2.16 eV, a high-energetic shoulder emerges. The difference between degraded and initial spectra (dotted curves) unveils that this recombination center has the same energy  ≈ 2.16 eV. The sample with [Si] = 59 at. % remains unaffected by the spectral degradation.

Image of FIG. 6.
FIG. 6.

The impact of Si = O on the degradation depends on the density of emerging trap states. The density of Si = O states is schematically represented by the red and blue bars. The higher the oxygen content, the higher is the density of Si = O trap states. For [Si] < 47 at. %, excited charge carriers are trapped at the Si = O states. Recombination is dominated by these localized states. In the range 51 at. % < [Si] < 55 at. %, only few excitons are trapped at the Si = O states. For [Si] > 59 at. %, the density of Si = O states is too low to affect the initial luminescence mechanism.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Origin and spectral degradation of the photoluminescence from a-SiOx