In situ spectroscopic ellipsometric investigation of vacuum annealed and oxidized porous silicon layers

M. Fried, Herbert Wormeester, E. Zoethout, T. Lohner, O. Polgar, I. Barsony

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Vacuum annealed and oxidized porous silicon layers (PSL) were investigated by in situ spectroscopic ellipsometry (SE). The nominal porosity of the layers was between 60 and 77% and the nominal thickness was 500 nm. The annealing was performed by direct ohmic heating (R.T.<450°C) in 5×10−10 Torr vacuum. The oxidation was performed in two steps, the first step at 5×10−5 Torr, the second at 10 Torr. Two optically different types of silicon compounds, a bulk-type silicon (c-Si) and a fine-grain polycrystalline silicon with enhanced absorption due to extensive grain-boundary regions (p-Si) were mixed with voids in the appropriate ratio to fit the spectra of as-prepared PSL. For the annealed PSL amorphous silicon (a-Si) was needed in conjunction with p-Si. The oxidized PSL could be fitted with a reduced a-Si content. We can interpret the annealing effect as a depassivation process of the inner surfaces of the PSL (a-Si fraction). At the same time, oxidation leads to a repassivation process.
Original languageEnglish
Pages (from-to)460-464
Number of pages5
JournalThin solid films
Issue number313
Publication statusPublished - 1998



  • IR-73674
  • Annealing
  • Porous Silicon
  • Oxidation
  • Spectroscopic ellipsometry
  • METIS-128688

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