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

M. Fried, H. Wormeester, E. Zoethout, T. Lohner, O. Polgár, I. Bársony

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Abstract

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)459-463
Number of pages5
JournalThin Solid Films
Volume313-314
DOIs
Publication statusPublished - Feb 13 1998

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Keywords

  • Annealing
  • Oxidation
  • Porous silicon
  • Spectroscopic ellipsometry

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

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