Tauc 图方法的局限性,Advanced Functional Materials

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Tauc 图方法的局限性
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2023-09-03 , DOI: 10.1002/adfm.202304523
Julian Klein ₁ , Laura Kampermann ₁ , Benjamin Mockenhaupt _{2,

3} , Malte Behrens _{2,

4} , Jennifer Strunk ₅ , Gerd Bacher ₁

Affiliation

Tauc图是一种最初开发用于推导非晶半导体（例如非晶锗或硅）的光学间隙的方法。通过测量吸收系数α ( hν ) 并绘图

{（ α H v ）}^{\frac{1}{2}} $(\alpha {hv})^{\frac{1}{2}}$

相对于光子能量hν ，光学间隙（Tauc 间隙）的值被确定。以这种方式，可以检查近似抛物线带之间的非直接光学跃迁。在过去的几十年中，这种针对（多）晶半导体的方法的修改已成为研究直接和间接带间跃迁的流行方法。为此， ( ahν ) ⁿ ( n =

\frac{1}{2} $\frac{1}{2}$

, 2) 相对于hν绘制以确定电子带隙的值。由于易于进行紫外-可见光测量，该方法现已成为分析各种（多）晶体固体的标准，无论其电子结构如何。尽管这部分导致名义上相同材料的各自带隙值存在很大差异，但仍然没有研究批判性地质疑电子结构中的哪些特性阻碍了（多）晶固体的Tauc 图的使用以及哪些材料类别这适用。本研究旨在通过讨论具有不同电子结构的示例性（多）晶固体的Tauc 图及其限制因素来缩小这一差距。

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Limitations of the Tauc Plot Method

The Tauc plot is a method originally developed to derive the optical gap of amorphous semiconductors such as amorphous germanium or silicon. By measuring the absorption coefficient α(hν) and plotting

{(α h v)}^{\frac{1}{2}} $(\alpha {hv})^{\frac{1}{2}}$

versus photon energy hν, a value for the optical gap (Tauc gap) is determined. In this way non-direct optical transitions between approximately parabolic bands can be examined. In the last decades, a modification of this method for (poly-) crystalline semiconductors has become popular to study direct and indirect interband transitions. For this purpose, (ahν)ⁿ (n =

\frac{1}{2} $\frac{1}{2}$

, 2) is plotted against hν to determine a value of the electronic bandgap. Due to the ease of performing UV–vis measurements, this method has nowadays become a standard to analyze various (poly-) crystalline solids, regardless of their different electronic structure. Although this leads partially to widely varying values of the respective bandgap of nominally identical materials, there is still no study that critically questions which peculiarities in the electronic structure prevent a use of the Tauc plot for (poly-) crystalline solids and to which material classes this applies. This study aims to close this gap by discussing the Tauc plot and its limiting factors for exemplary (poly-) crystalline solids with different electronic structures.

更新日期：2023-09-03

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