Application of the Holomorphic Tauc-Lorentz-Urbach Function to Extract the Optical Constants of Amorphous Semiconductor Thin Films

Manuel Ballester, Marcos García, Almudena P. Márquez, Eduardo Blanco, Susana M. Fernández, Dorian Minkov, Aggelos K. Katsaggelos, Oliver Cossairt, Florian Willomitzer, Emilio Márquez*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The Tauc–Lorentz–Urbach (TLU) dispersion model allows us to build a dielectric function from only a few parameters. However, this dielectric function is non-analytic and presents some mathematical drawbacks. As a consequence of this issue, the model becomes inaccurate. In the present work, we will adopt a procedure to conveniently transform the TLU model into a self-consistent dispersion model. The transformation involves the integration of the original TLU imaginary dielectric function (Formula presented.) by using a Lorentzian-type function of semi-width, (Formula presented.). This novel model is analytic and obeys the other necessary mathematical requirements of the optical constants of solid-state materials. The main difference with the non-analytic TLU model occurs at values of the photon energy near or lower than that of the bandgap energy (within the Urbach absorption region). In particular, this new model allows us to reliably extend the optical characterization of amorphous-semiconductor thin films within the limit to zero photon energy. To the best of our knowledge, this is the first time that the analytic TLU model has been successfully used to accurately determine the optical constants of unhydrogenated a-Si films using only their normal-incidence transmission spectra.

Original languageEnglish (US)
Article number1549
JournalCoatings
Volume12
Issue number10
DOIs
StatePublished - Oct 2022

Keywords

  • amorphous semiconductors
  • dielectric function
  • optical properties
  • Tauc–Lorentz model
  • Tauc–Lorentz–Urbach model
  • thin-film characterization

ASJC Scopus subject areas

  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

Fingerprint

Dive into the research topics of 'Application of the Holomorphic Tauc-Lorentz-Urbach Function to Extract the Optical Constants of Amorphous Semiconductor Thin Films'. Together they form a unique fingerprint.

Cite this