Band structures and optical properties related to substitutional impurities in TlGaSe<sub>2</sub> layered crystals: first-principles study

Kharkhalis, L. Yu.; Глухов, К. Э.; Babuka, T.; Liakh, M. V.

doi:10.1080/01411594.2019.1583339

Cited by 7 publications

(8 citation statements)

References 32 publications

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“…The simulation was carried out for fully geometry optimized structure, i.e., the lattice parameters and atomic positions were relaxed under preserved symmetry. As was shown already in previous papers concerning materials characterized by a vdW gap [14][15][16], the inclusion of the dispersion correction in the DFT calculations gives a possibility to describe in a correct way interlayer distances. As a result, the obtained relaxed TlInS 2 structural parameters are as follows, a = b = 7.783385 Å, c = 15.267074 Å, α = β = 96.882950 • , γ = 90.035269 • , V = 911.507392 Å 3 .…”

Section: First-principle Calculation Results Of the Electronic Propermentioning

confidence: 69%

Electronic and Optical Properties of the TlInS₂ Crystal: Theoretical and Experimental Studies

et al. 2019

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Investigations on the electronic and optical properties of a TlInS2 layered crystal in the framework of density functional theory were carried out. The electronic band spectrum and the partial density of states were calculated including the dispersion correction. The impact of +U correction term on the bandgap values was analyzed as well. Based on the band structure calculations, optical characterisation was made for the first time for TlInS2, such as the real and imaginary parts of the dielectric function, the refractive index, and the absorption coefficient. Theoretical results of dielectric function and refractive index were compared to the measurement results.

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Section: First-principle Calculation Results Of the Electronic Propermentioning

confidence: 69%

Electronic and Optical Properties of the TlInS₂ Crystal: Theoretical and Experimental Studies

et al. 2019

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“…The stoichiometric TlGaSe 2 bulk sample is a brick -red compound. The first -principles electronic band structure calculations demonstrate that the perfect monolayer of TlGaSe 2 must exhibit a direct energy band gap at G -point of the Brillouin zone [4,[31][32][33][34][35][36][37]. It is also important to mention that the experimentally evaluated band gap values for undoped TlGaSe 2 samples are large enough than expected for a brick -red colored compound.…”

Section: Introductionmentioning

confidence: 89%

Modification of the optical and elastic properties of TlGaSe₂ layered semiconductor produced by the memory effect

Cengiz,

Gören,

Sönmez

et al. 2023

Phys. Scr.

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A comparative analysis of the temperature behaviors of optical and elastic properties of TlGa Se 2 single crystals under a memory effect experimental condition are presented for the first time. A memory effect condition suggests that the sample is thermally annealed inside the incommensurate (INC) phase for a time interval the corresponding physical parameters is measured experimentally. From ultrasound velocity measurements, carried out before and after the thermal annealing process subjected to the sample, the noticeable changes in the temperature variation of the longitudinal ultrasonic wave velocity associated with the elastic constants C 33 of TlGa Se 2 due to the memory effect was detected. Our results reveal that thermal annealing performed at the INC - phase has some influence on the optical absorption of TlGa Se 2 crystals in the visible spectral region. We assumed that thermal annealing within INC - phase is accompanied with the appearance, inside TlGa Se 2 samples, a new quasiperiodic frozen structure formed from the intrinsic defects migrated into the lowest energy diffusion barriers of the INC - modulation wave. Such structural modulation is incommensurate with the underlying lattice of TlGa Se 2 and can lead to changes in the electronic band structure and the optical bandgaps of TlGa Se 2 .

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“…By analyzing the above optical data, we can obtain information about modifying the fundamental absorption edge of the TlGaSe 2 crystal induced by the electric field poling. Although the undoped TlGaSe 2 semiconductor is a direct bandgap material with a fundamental absorption edge ranging between about E d g ∼ 2.0-2.2 eV at ambient temperature and pressure, some researchers have assumed that TlGaSe 2 is an indirect bandgap semiconductor with a bandgap width varying from ∼1.8 to ∼2.0 eV [25,[56][57][58][59]. As is well known, phononassisted optical transitions occur in indirect bandgap semiconductor materials [56][57][58][59].…”

Section: Optical Absorption Measurementsmentioning

confidence: 99%

“…Although the undoped TlGaSe 2 semiconductor is a direct bandgap material with a fundamental absorption edge ranging between about E d g ∼ 2.0-2.2 eV at ambient temperature and pressure, some researchers have assumed that TlGaSe 2 is an indirect bandgap semiconductor with a bandgap width varying from ∼1.8 to ∼2.0 eV [25,[56][57][58][59]. As is well known, phononassisted optical transitions occur in indirect bandgap semiconductor materials [56][57][58][59]. In contrast to the indirect energy bandgap model, it has been recently suggested that intrinsic imperfections of the undoped TlGaSe 2 crystal, such as Se vacancies, may introduce the defect-induced electronic levels inside the bandgap of TlGaSe 2 with the absolute energy minimum located away from the center of the Brillouin zone [25].…”

Section: Optical Absorption Measurementsmentioning

confidence: 99%

The Franz–Keldysh effect in the optical absorption spectrum of a TlGaSe₂ layered semiconductor caused by charged native defects

Gören,

Şale,

Seyidov

2024

Semicond. Sci. Technol.

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The Franz-Keldysh effect in the optical absorption edge of bulk TlGaSe2 layered semiconductor poled under an external electric field was investigated in the present work. The Franz-Keldysh shift below the optical band gap absorption region, as well as the quasi-periodic oscillations above the fundamental band gap of TlGaSe2, were observed. The measured changes in optical light absorption of the TlGaSe2 sample were revealed after poling processing. The poling technique is used to produce the built-in internal electric field within the TlGaSe2 semiconductor. The frozen-in internal electric field in TlGaSe2 was experimentally monitored through changes in the line–shape of the absorption spectra at the fundamental band edge. The observed results are accurately fitted with the theoretical line-shape function of the Franz - Keldysh absorption tail below the bandgap of TlGaSe2 and quasi-periodic oscillations above the bandgap. A good agreement between theoretical and experimental results took place. The present study demonstrated that the Franz - Keldysh effect can be used to identify and characterize the localized internal electric fields originating from the electrically active native imperfections in the TlGaSe2 crystals.

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Band structures and optical properties related to substitutional impurities in TlGaSe₂ layered crystals: first-principles study

Cited by 7 publications

References 32 publications

Electronic and Optical Properties of the TlInS₂ Crystal: Theoretical and Experimental Studies

Electronic and Optical Properties of the TlInS₂ Crystal: Theoretical and Experimental Studies

Modification of the optical and elastic properties of TlGaSe₂ layered semiconductor produced by the memory effect

The Franz–Keldysh effect in the optical absorption spectrum of a TlGaSe₂ layered semiconductor caused by charged native defects

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Band structures and optical properties related to substitutional impurities in TlGaSe2 layered crystals: first-principles study

Cited by 7 publications

References 32 publications

Electronic and Optical Properties of the TlInS2 Crystal: Theoretical and Experimental Studies

Electronic and Optical Properties of the TlInS2 Crystal: Theoretical and Experimental Studies

Modification of the optical and elastic properties of TlGaSe2 layered semiconductor produced by the memory effect

The Franz–Keldysh effect in the optical absorption spectrum of a TlGaSe2 layered semiconductor caused by charged native defects

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Band structures and optical properties related to substitutional impurities in TlGaSe₂ layered crystals: first-principles study

Electronic and Optical Properties of the TlInS₂ Crystal: Theoretical and Experimental Studies

Electronic and Optical Properties of the TlInS₂ Crystal: Theoretical and Experimental Studies

Modification of the optical and elastic properties of TlGaSe₂ layered semiconductor produced by the memory effect

The Franz–Keldysh effect in the optical absorption spectrum of a TlGaSe₂ layered semiconductor caused by charged native defects