Determination of complex dielectric functions of ion implanted and implanted-annealed amorphous silicon by spectroscopic ellipsometry

M. Fried, T. Lohner, W. A.M. Aarnink, L. J. Hanekamp, A. Van Silfhout

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Abstract

Measuring with a spectroscopic ellipsometer (SE) in the 1.8-4.5 eV photon energy region we determined the complex dielectric function (ε = ε1 + iε2) of different kinds of amorphous silicon prepared by self-implantation and thermal relaxation (500°C, 3 h). These measurements show that the complex dielectric function (and thus the complex refractive index) of implanted a-Si (i-a-Si) differs from that of relaxed (annealed) a-Si (r-a-Si). Moreover, its ε differs from the ε of evaporated a-Si (e-a-Si) found in the handbooks as ε for a-Si. If we use this ε to evaluate SE measurements of ion implanted silicon then the fit is very poor. We deduced the optical band gap of these materials using the Davis-Mott plot based on the relation: (ε2E2) 1/3 ∼ (E- Eg). The results are: 0.85 eV (i-a-Si), 1.12 eV (e-a-Si), 1.30 eV (r-a-Si). We attribute the optical change to annihilation of point defects.

Original languageEnglish
Pages (from-to)5260-5262
Number of pages3
JournalJournal of Applied Physics
Volume71
Issue number10
DOIs
Publication statusPublished - Dec 1 1992

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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