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Temperature Dependence of the Photoluminescence from Ensembles of Amorphous Silicon Nanoparticles with Various Average Sizes

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Abstract:

Amorphous SiOx thin films with three different oxygen contents (x = 1.3, 1.5, and 1.7) have been deposited by thermal evaporation of SiO in vacuum. Partial phase separation in the films has been induced by annealing at 773 or 973 K in argon for 60 and 120 min and thus Si-SiOx composite films have been prepared containing amorphous Si nanoparticles of various sizes (<3 nm). Photoluminescence from the films has been measured in the temperature range 20–296 K. The single Gauss band observed in the photoluminescence spectra of the samples with x = 1.3 and centered in the range 1.55–1.75 eV has been related to radiative recombination in Si nanoparticles. Two bands, a red-orange one (related to radiative recombination in Si nanoparticles) and a green band peaked at ∼2.3 eV (related to radiative recombination via defects) have been resolved in the photoluminescence spectra of the films with x = 1.5 and 1.7. The band in the spectra of the x = 1.3 samples has shown a relative strong thermal quenching but it is significantly weaker than the photoluminescence quenching in bulk a-Si. Besides, the higher the initial oxygen content, the weaker is the photoluminescence thermal quenching. These observations have been related to carrier confinement which is stronger in smaller nanoparticles. The thermally induced photoluminescence decrease with increasing temperature in the samples with x = 1.3 obeys the relation that is characteristic for bulk a-Si:H while the photoluminescence decrease in x = 1.5 and 1.7 samples is of Arrhenius type. We suggest that in nanoparticles larger than 2 nm recombination via band tail states is the dominating photoluminescence mechanism while in smaller nanoparticles exciton-like recombination dominates.

Keywords: AMORPHOUS SILICON; NANOCRYSTALS; NANOPARTICLES; PHOTOLUMINESCENCE; SILICON; SIZE-DEPENDENCE

Document Type: Research Article

DOI: https://doi.org/10.1166/jnn.2011.3103

Publication date: 2011-02-01

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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