Methodological Investigation of the Band Gap Determination of Solid Semiconductors via UV/Vis Spectroscopy

Welter, Eike S.; Garg, Seema; Gläser, Roger; Goepel, Michael

doi:10.1002/cptc.202300001

Cited by 14 publications

(1 citation statement)

References 92 publications

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“…The few studies dealing with a critical evaluation of the Tauc plot method consider selected materials (i.e., ZnO, TiO 2 ) and follow a mathematical approach. [20][21][22] It was investigated, for example, how the respective bandgaps for a combination of two materials can be calculated or which steepness the absorption edge must have to be able to successfully determine a bandgap value by a Tauc plot. Other critical studies of the Tauc plot method primarily present alternative methods of evaluating optical absorption spectra.…”

Section: Introductionmentioning

confidence: 99%

Limitations of the Tauc Plot Method

Klein,

Kampermann,

Mockenhaupt

et al. 2023

Adv Funct Materials

128

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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 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 = , 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.

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Section: Introductionmentioning

confidence: 99%

Limitations of the Tauc Plot Method

Klein,

Kampermann,

Mockenhaupt

et al. 2023

Adv Funct Materials

128

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Efficient Separation of Adjacent Rare Earths in One Step by Using Ion‐microporous Metal–Organic Frameworks

Song,

Yang,

et al. 2024

Adv Funct Materials

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High‐purity rare earth (REEs) materials are key raw materials for the development of cutting‐edge technologies. However, due to similar physical and chemical properties, separating adjacent REEs from actual samples faces a formidable challenge. To overcome this challenge, an ion‐microporous metal–organic framework (ATZ‐BTC‐Zn; MOFs) is designed and synthesized, featuring densely packed nano‐trap pockets constructed from non‐coordinating carboxyl and amino groups. The synergistic effect of open nano‐trap pockets and suitable ions channel in ATZ‐BTC‐Zn is highly responsive to the size variation of lighter REEs. Notably, the configuration of Zn(H2O)62+ counterion in ATZ‐BTC‐Zn is similar to lanthanide hydrated ions (Ln(H2O)63+), facilitating the efficient ion exchange between them in the high‐speed ion transport channel. This accelerates the diffusion of REEs within the MOF pores, enhancing the utilization of active adsorption sites and promoting the efficient capture of adjacent REEs by nano‐traps. The binary model experiments show high separation factors for adjacent REEs (SFLa/Nd = 908, SFCe/La = 543), demonstrating efficient separation by ATZ‐BTC‐Zn in one step. This capability achieves the selective separation of adjacent REEs in tailings wastewater, providing a strategy to infer the compatibility between MOFs and REEs.

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Investigation of Optical Properties of Pentasodium Trioxoundecafluoro‐Trititanate for Optoelectronic Applications

Mbulanga,

Erasmus,

Ahia

et al. 2024

Physica Status Solidi (a)

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A successful application of the Kubelka–Munk model, modified Kubelka–Munk model and unified methodology for estimating the bandgap in semiconducting materials to the analysis of diffuse reflectance spectra for pentasodium trioxoundecafluoro‐trititanate (Na5(Ti3O3F11)) plates grown using a hydrothermal method is reported. The steps involved in interpreting the Kubelka–Munk F(R) function and using it for bandgap determination are presented. Bandgap energy (Eg) calculations are performed after establishing, through an extensive literature review, that (i) values can be obtained by extrapolating a linear fit of the Tauc diagram to zero–using the photon energy axis as the abscissa–for a sample that exhibits negligible absorption of gaps in the sub‐bands, but (ii) if absorption of gaps in the sub‐bands is observed in the Tauc diagram, a linear fit of the Tauc diagram can be performed as in the method described in (i). In addition, another linear line fit is added and used as a new abscissa to replace the photon energy axis used in point (ii). It is established that pentasodium trioxoundecafluoro‐trititanate is a wide‐bandgap material, with bandgap energies of 3.70 eV (p = 1/2) and 4.0 eV (p = 2), respectively.

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Methodological Investigation of the Band Gap Determination of Solid Semiconductors via UV/Vis Spectroscopy

Cited by 14 publications

References 92 publications

Limitations of the Tauc Plot Method

Limitations of the Tauc Plot Method

Efficient Separation of Adjacent Rare Earths in One Step by Using Ion‐microporous Metal–Organic Frameworks

Investigation of Optical Properties of Pentasodium Trioxoundecafluoro‐Trititanate for Optoelectronic Applications

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