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Assessing Tauc Plot Slope Quantification: ZnO Thin Films as a Model System
Author(s) -
Coulter Jennifer B.,
Birnie Dunbar P.
Publication year - 2018
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201700393
Subject(s) - plot (graphics) , band gap , materials science , analytical chemistry (journal) , magnitude (astronomy) , thin film , absorption edge , optics , mathematics , physics , statistics , chemistry , nanotechnology , optoelectronics , chromatography , astronomy
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 where the intercept gives the band gap and the fitting exponent identifies the electronic transition as direct or indirect. [See Tauc et al., Physica Status Solidi 15, 627 (1966); naturally, these are usually called “Tauc” plots.] In earlier work, we found that direct band gaps fitted using Tauc's method can be quite accurate, to ∼1% [see Viezbicke et al., Phys. Status Solidi B 252, 1700 (2015)]. Still, slopes of these Tauc plots are less frequently quantified, even though the slopes are directly rooted in key band‐structure parameters. In this study, we examine the reproducibility of Tauc plot slopes for ZnO as a model direct‐gap material and compare these experimental values with the theoretically derived slope. In contrast to the band gap accuracy, the experimental slope values varied by several orders of magnitude. The histogram of slope values was significantly more compact for Tauc plots exhibiting less Urbach tail contribution. In these cases, the Tauc slopes can provide an order‐of‐magnitude quantification of other key band characteristics such as carrier effective mass.