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 language | English |
|---|---|
| Pages (from-to) | 1700-1710 |
| Number of pages | 11 |
| Journal | Physica Status Solidi (B) Basic Research |
| Volume | 252 |
| Issue number | 8 |
| DOIs | |
| Publication status | Published - Aug 1 2015 |
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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 journal › Article
}
TY - JOUR
T1 - Evaluation of the Tauc method for optical absorption edge determination
T2 - ZnO thin films as a model system
AU - Viezbicke, Brian D.
AU - Patel, Shane
AU - Davis, Benjamin E.
AU - Birnie, Dunbar P
PY - 2015/8/1
Y1 - 2015/8/1
N2 - 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.
AB - 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.
KW - Band gaps
KW - Near-edge absorptivity ratio
KW - Optical absorption
KW - Polycrystalline semiconductors
KW - Tauc plots
KW - Thin films
KW - ZnO
UR - http://www.scopus.com/inward/record.url?scp=84938526316&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84938526316&partnerID=8YFLogxK
U2 - 10.1002/pssb.201552007
DO - 10.1002/pssb.201552007
M3 - Article
VL - 252
SP - 1700
EP - 1710
JO - Physica Status Solidi (B): Basic Research
JF - Physica Status Solidi (B): Basic Research
SN - 0370-1972
IS - 8
ER -