Evaluation of the Tauc method for optical absorption edge determination

ZnO thin films as a model system

Brian D. Viezbicke, Shane Patel, Benjamin E. Davis, Dunbar P Birnie

Research output: Contribution to journalArticle

172 Citations (Scopus)

Abstract

One of the most frequently used methods for characterizing thin films is UV-Vis absorption. The near-edge region can be fitted to a simple expression in which the intercept gives the band-gap and the fitting exponent identifies the electronic transition as direct or indirect (see Tauc et al., Phys. Status Solidi 15, 627 (1966); these are often called "Tauc" plots). While the technique is powerful and simple, the accuracy of the fitted band-gap result is seldom stated or known. We tackle this question by refitting a large number of Tauc plots from the literature and look for trends. Nominally pure zinc oxide (ZnO) was chosen as a material with limited intrinsic deviation from stoichiometry and which has been widely studied. Our examination of the band gap values and their distribution leads to a discussion of some experimental factors that can bias the data and lead to either smaller or larger apparent values than would be expected. Finally, an easily evaluated figure-of-merit is defined that may help guide more accurate Tauc fitting. For samples with relatively sharper Tauc plot shapes, the population yields Eg(ZnO) as 3.276±0.033eV, in good agreement with data for single crystalline material.

Original languageEnglish
Pages (from-to)1700-1710
Number of pages11
JournalPhysica Status Solidi (B) Basic Research
Volume252
Issue number8
DOIs
Publication statusPublished - Aug 1 2015

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Zinc Oxide
Zinc oxide
zinc oxides
Light absorption
Oxide films
Energy gap
optical absorption
plots
Thin films
evaluation
thin films
figure of merit
Stoichiometry
stoichiometry
examination
exponents
Crystalline materials
deviation
trends
electronics

Keywords

  • Band gaps
  • Near-edge absorptivity ratio
  • Optical absorption
  • Polycrystalline semiconductors
  • Tauc plots
  • Thin films
  • ZnO

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Evaluation of the Tauc method for optical absorption edge determination : ZnO thin films as a model system. / Viezbicke, Brian D.; Patel, Shane; Davis, Benjamin E.; Birnie, Dunbar P.

In: Physica Status Solidi (B) Basic Research, Vol. 252, No. 8, 01.08.2015, p. 1700-1710.

Research output: Contribution to journalArticle

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