Assessing Tauc Plot Slope Quantification: ZnO Thin Films as a Model System

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 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.

PVA assisted ZnO based mesoporous ternary metal oxides nanomaterials: synthesis, optimization, and evaluation of antibacterial activity

“…The nature of the direct allowed/direct forbidden and indirect allowed/indirect forbidden electronic transition is dependent on the 1/n value. The 1/2, 3/2, 2, and 3 are the values for direct allowed, direct forbidden, indirect allowed, and indirect forbidden, respectively [23]. The direct allowed transition for code 90(0.4) and 50(0.7) was determined to be 3.23 and 3.32 eV, and the indirect allowed transition is obtained to be 3.03 and 2.99 eV, respectively.…”

Growth of 4-N,N-Dimethylamino-4'-N'-methyl-stilbazolium Tosylate (DAST) Organic Single Crystals Controlled by Oleic Acid

“…The smaller NEAR value suggests lower defect density in a material [27]. Further calculations about the related NEAR value in our work reveal that the NEAR of the crystal grown without the OA control was calculated to be 0.92, while a lower NEAR of 0.86 was estimated from the crystal grown under the control of the OA.…”

“…According to the results reported by Mondal et al [26], the reduction in the slope of the linear portion of the Tauc plot suggests the introduction of defect states within the band gap, due to the coupling of an impurity band into the conduction band, thus reducing the optical band gap. According to the UV-vis measurement results, the defect density can be further semi-quantitatively investigated by a near edge absorptivity ratio (NEAR) [27]:…”

Magnesium Incorporation in n-CdTe to Produce Wide Bandgap p-Type CdTe:Mg Window Layers

“…According to Figure 6a, with the increase of Mg inclusion to the ED bath there appears a gradual disappearance of typical absorption point of CdTe (~1.45 eV) when the growth voltage has been kept constant at 1400 mV. The steepness of the slope at the absorption edge weakens gradually which may indicate a presence of high defect state [20,21]. The graph also depicts that at a high (~50%) Mg concentration in the bath, the grown layer does not demonstrate any absorption around the typical CdTe absorption point, therefore indicates a change in the band gap energy.…”