Temperature-dependent absorption edge in AgGaS2 compound semiconductor

Eom, Sung‐Hwan; Kim, D.J.; Yu, Young‐Moon; Choi, Yong Dae

doi:10.1016/j.jallcom.2004.07.031

Cited by 12 publications

(9 citation statements)

References 36 publications

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“…For most compound semiconductors, the temperature dependence of the energy band gap can be described using an empirical relation such as the Varshni equation . An anomalous blue‐shift of the band gap energy has been observed for some copper‐ and silver‐based chalcogenide compounds at low temperature . More recently, although the transition energy values were slightly different, Raadik et al have observed the blue‐shift of A‐band with increasing temperature from 10 to 130 K. However, considering the strong absorption tailing, the temperature‐dependent band gap energy could not be evaluated precisely for the Cu‐poor CTS thin film in the present study.…”

Section: Resultsmentioning

confidence: 99%

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu₂SnS₃ Thin Films

Aihara

Araki

Tanaka

2017

Physica Status Solidi (b)

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Temperature‐dependent optical absorption spectra from transmittance and reflectance measurements of Cu2SnS3 (CTS) thin films which are promising material for solar cells were investigated. Thin film CTS samples with Cu‐poor, near‐stoichiometric, and Cu‐rich compositions were prepared on glass substrates by thermal co‐evaporation and sulfurization. At low temperature, three band‐to‐band (BB) transitions that are allowed between triple upper valence bands and a single lower conduction band were observed for all samples. The square of the product of the absorption coefficient and the photon energy was plotted to estimate the band gap energy for three bands of the Cu‐poor sample. On the other hand, excitonic (EX) transitions that corresponded to three bands were observed for the Cu‐rich and near‐stoichiometric samples. Temperature‐dependent optical absorption spectra with the triple BB and EX transitions were resolved using a simplified fitting equation with Lorentzian functions as the EX transitions. The band gap, EX transition, and exciton binding energies for the lowest energy band of the Cu‐rich sample were determined to be 0.945 eV, 0.936 eV, and 8.9 meV at 6 K, respectively. In the low‐temperature region, anomalous blue‐shifts of the estimated band gap energy with increasing temperature were obtained for three bands of all samples.

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Section: Resultsmentioning

confidence: 99%

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu₂SnS₃ Thin Films

Aihara

Araki

Tanaka

2017

Physica Status Solidi (b)

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“…In contrast, chromium strongly influences the positioning in energy of the charge transfer. Indeed, the O 2-Cr 3+ charge transfer is expected to take place at a lower energy than the O 2-Fe 3+ one because the 3d 4 high spin electronic configuration of Cr 2+ ions is expected to lye below the 3d 6 high spin configuration of Fe 2+ cations 31 . Consequently, the Cr 3+ /Fe 3+ substitution simulates a temperature increase, the higher the substitution rate, the more red-shifted the charge transfer.…”

Section: Optical Properties Of Cr-doped Y 3 Fe 5 O 12mentioning

confidence: 99%

“…For oxide compounds, reversible thermochromism can be explained by a gradual reduction of the semiconductors band-gap 4 with a temperature increase (red-shift), or a crystallographic phase transition and/or an insulator/metal transition [5][6][7][8][9] . The restriction of semiconductors lies in the limited color choice and the likely slight color contrast due to a continuous variation of the color from pale yellow to red.…”

Section: Introductionmentioning

confidence: 99%

Thermochromism in Yttrium Iron Garnet Compounds

et al. 2014

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Polycrystalline yttrium iron garnet (Y3Fe5O12, hereafter labeled YIG) has been synthesized by solid-state reaction, characterized by X-ray diffraction, Mössbauer spectroscopy, and UV-vis-NIR diffuse reflectance spectroscopy, and its optical properties from room temperature (RT) to 300 °C are discussed. Namely, its greenish color at RT is assigned to an O(2-) → Fe(3+) ligand-to-metal charge transfer at 2.57 eV coupled with d-d transitions peaking at 1.35 and 2.04 eV. When the temperature is raised, YIG displays a marked thermochromic effect; i.e., the color changes continuously from greenish to brownish, which offers opportunities for potential application as a temperature indicator for everyday uses. The origin of the observed thermochromism is assigned to a gradual red shift of the ligand-to-metal charge transfer with temperature while the positioning in energy of the d-d transitions is almost unaltered. Attempts to achieve more saturated colors via doping (e.g., Al(3+), Ga(3+), Mn(3+), ...) remained unsuccessful except for chromium. Indeed, Y3Fe5O12:Cr samples exhibit at RT the same color than the undoped garnet at 200 °C. The introduction of Cr(3+) ions strongly impacts the color of the Y3Fe5O12 parent either by an inductive effect or, more probably, by a direct effect on the electronic structure of the undoped material with formation of a midgap state.

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“…where hν p is the energy of the phonons associated with Urbach's tail and σ 0 a constant. Different values of hν p for the same material, some of them much higher than the highest optical mode observed in the vibrational spectra of each material, have been reported in ternary chalcopyrite [18,[20][21][22] and chalcopyrite-related structure compounds [23][24][25][26]. The existence of these unusually higher energy modes is explained by assuming that they are due to the structural disorder caused by the deviation from ideal molecularity and valence stoichiometry in the samples studied [18].…”

Section: Theorymentioning

confidence: 84%

Urbach’s tail in the absorption spectra of Cu2GeSe3 semiconducting compound

et al. 2018

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In the present work we report on the analysis of the Urbach’s tail in pure and Mn-doped Cu2GeSe3 samples having small deviation from its ideal stoichiometry. It is found that the high values of the phonon energy hnp involved in the electrons/excitons-phonon interaction in the formation of this tail are due to structural disorder caused by deviation from ideal stoichiometry. Values of hnp for pure and doped samples were found to be 48, 60 and 81 meV, respectively, whereas the phonon energy for an entirely ordered Cu2GeSe3 sample was estimated to be about 25 meV.

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Temperature-dependent absorption edge in AgGaS2 compound semiconductor

Cited by 12 publications

References 36 publications

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu₂SnS₃ Thin Films

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu₂SnS₃ Thin Films

Thermochromism in Yttrium Iron Garnet Compounds

Urbach’s tail in the absorption spectra of Cu2GeSe3 semiconducting compound

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Temperature-dependent absorption edge in AgGaS2 compound semiconductor

Cited by 12 publications

References 36 publications

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu2SnS3 Thin Films

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu2SnS3 Thin Films

Thermochromism in Yttrium Iron Garnet Compounds

Urbach’s tail in the absorption spectra of Cu2GeSe3 semiconducting compound

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Product

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Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu₂SnS₃ Thin Films

Excitonic and Band‐to‐Band Transitions in Temperature‐Dependent Optical Absorption Spectra of Cu₂SnS₃ Thin Films