Vacancy ordering of Ga2Se3 films by molecular beam epitaxy

Teraguchi, N.; Kato, F.; Konagai, Makoto; Takahashi, Kiyoshi; Nakamura, Yoshio; Ōtsuka, N.

doi:10.1063/1.105388

Cited by 41 publications

(14 citation statements)

References 13 publications

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“…During the deposition of Ga‐Se at 620 K, the main reflexes can be attributed to the α‐Ga 2 Se 3 (ICDD card 03‐65‐6161) phase (Figure 4b). The α‐Ga 2 Se 3 crystallizes in a structure similar to that of zinc blende, where Ga vacancies are distributed randomly on the metallic sublattice and the Se atomic layers are organized following an ABCABC type stacking 17. Again, the measured lattice spacings are larger than the reported ones due to the higher temperature of the measurement (620 K) compared to that of the reference (300 K).…”

Section: Resultsmentioning

confidence: 77%

Formation of CuInSe₂ and CuGaSe₂ Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Rodríguez-Alvarez

Weber

Lauche

et al. 2013

Advanced Energy Materials

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Thin film solar cells based on co‐evaporated Cu(In,Ga)Se2 absorber films present the highest efficiencies among current polycrystalline thin‐film technologies. Thanks to the development of a novel experimental setup for in situ growth studies, it was possible to follow the formation of the crystalline phases during such deposition processes for the first time. This synchrotron‐based energy‐dispersive X‐ray diffraction and fluorescence setup is suited for real‐time studies of thin film vapor deposition processes. Focusing on the growth of CuInSe2 and CuGaSe2 fabricated by three‐stage processing, we find that the phase transitions in the Cu‐In‐Se system follow the reported pseudo‐binary In2Se3‐Cu2Se phase diagram. This requires a transformation of the Se sublattice during the incorporation of Cu‐Se into the In2Se3 precursor film from the first process stage. In the Cu‐Ga‐Se system, besides an increase in the lattice spacings, we observe no transformation of the Se sublattice. Furthermore, the structural defects of the Ga‐Se precursor film are preserved until the CuGaSe2 stoichiometry is reached. By means of model calculations of the fluorescence signals, we confirm in both systems the segregation of Cu2Se at the surface near a concentration of 25 at.% Cu shortly after the recrystallization of the films. The modeling also reveals that Cu2Se penetrates into the CuInSe2 film, whereas it remains at the surface of the CuGaSe2 film.

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Section: Resultsmentioning

confidence: 77%

Formation of CuInSe₂ and CuGaSe₂ Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Rodríguez-Alvarez

Weber

Lauche

et al. 2013

Advanced Energy Materials

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“…7 It has been expected that Ga 2 Te 3 and Ga 2 Se 3 have a mesoscopic superstructured phase, having vacancy planes. 8,9 In our previous studies, 10,11 the existence of regularly arranged two-dimensional (2D) vacancy planes with approximately 10 lattice (equivalent to 3.5 nm) intervals was confirmed in Ga 2 Te 3 . 10 Furthermore, in solid solutions of (Ga,In) 2 Te 3 , such vacancy planes also existed, but the periodicity of the intervals was random.…”

Section: Introductionmentioning

confidence: 70%

Effect of Vacancy Distribution on the Thermal Conductivity of Ga2Te3 and Ga2Se3

Kim

Kurosaki

Ishimaru

et al. 2011

Journal of Elec Materi

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“…[1][2][3] When epitaxialized, for example, Ga 2 Se 3 has an orthorhombic defect zinc-blende structure, [4][5][6] where every atom is located at the zinc-blende site and one third of the cation sites are occupied by the vacancies. Since the vacancies form an array along the [110] direction, the characteristic electronic properties are expected compared to the familiar zinc-blende and chalcopyrite semiconductors.…”

Section: §1 Introductionmentioning

confidence: 99%

Raman Spectra Calculation of Ordered-Vacancy Ga₂Se₃Compounds; Origin of Anisotropy

2000

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Polarized Raman spectra of ordered-vacancy Ga 2 Se 3 were calculated using the sp 3 s * tightbinding and vibration models. We found a large peak around 150 cm −1 which originates from the breathing-like movement of Se atoms around the vacancy. Reflecting the localized nature of vibration and the dangling-bond direction of three-coordinated Se atoms, this peak shows large intensity and anisotropy; the intensity is large for the light polarization perpendicular to the vacancy array, in contrast to the anisotropy observed in the photo-absorption and luminescence. These results well explain the experiments.Due to the misvalency between III and VI atoms, III 2 IV 3 compounds show a variety of crystal polymorphism depending on the growth condition. 1-3) When epitaxialized, for example, Ga 2 Se 3 has an orthorhombic defect zinc-blende structure, 4-6) where every atom is located at the zinc-blende site and one third of the cation sites are occupied by the vacancies. Since the vacancies form an array along the [110] direction, the characteristic electronic properties are expected compared to the familiar zinc-blende and chalcopyrite semiconductors. In fact, Okamoto et al. found that both the photo-absorption and luminescence around the fundamental band-gap energy are extremely anisotropic; they are large for the light polarization parallel to the vacancy array. 7, 8) Nakayama and Ishikawa calculated the electronic structures and the absorption spectra of this system, 9) and clarified that the dangling bonds of twocoordinated Se produce one-dimensional band along the [110] direction at the valence band top and the optical transitions from this band become the origin of such anisotropy.On the other hand, to clarify the crystal quality of MBE-grown orthorhombic Ga 2 Se 3 , Yamada et al. carried out the polarized Raman spectrum experiment in a back-scattering geometry. 6, 10) They found that there appears a large peak around 155 cm −1 and its intensity is large for the light polarization perpendicular to the vacancy array, in contrast to the cases of photoabsorption and luminescence. 7, 8) Using a simple vibration model with the interatomic force constants, they assigned that this peak originates from the A 1 -symmetry vibration mode and supposed that such mode is closely related to the vacancy array. However, the origins of the observed large intensity and the different anisotropy from that in the photo-absorption and emission have not been clarified yet. The purpose of this paper is to clarify 3860 these origins by calculating polarized Raman spectra of orthorhombic Ga 2 Se 3 , using the simple vibration model for phonons and the tight-binding method for electronic structures. §2. Geometry and Calculational Method Figure 1 shows the schematic picture of orthorhombic Ga 2 Se 3 viewed from the [001] direction. The unit cell denoted by the arrows is three times large along y compared to x, where x and y denote the [110] and [110] directions, respectively. Vacancies are arranged along x and this system has C 20 2v symmetry. I...

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Vacancy ordering of Ga2Se3 films by molecular beam epitaxy

Cited by 41 publications

References 13 publications

Formation of CuInSe₂ and CuGaSe₂ Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Formation of CuInSe₂ and CuGaSe₂ Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Effect of Vacancy Distribution on the Thermal Conductivity of Ga2Te3 and Ga2Se3

Raman Spectra Calculation of Ordered-Vacancy Ga₂Se₃Compounds; Origin of Anisotropy

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Vacancy ordering of Ga2Se3 films by molecular beam epitaxy

Cited by 41 publications

References 13 publications

Formation of CuInSe2 and CuGaSe2 Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Formation of CuInSe2 and CuGaSe2 Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Effect of Vacancy Distribution on the Thermal Conductivity of Ga2Te3 and Ga2Se3

Raman Spectra Calculation of Ordered-Vacancy Ga2Se3Compounds; Origin of Anisotropy

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Formation of CuInSe₂ and CuGaSe₂ Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Formation of CuInSe₂ and CuGaSe₂ Thin‐Films Deposited by Three‐Stage Thermal Co‐Evaporation: A Real‐Time X‐Ray Diffraction and Fluorescence Study

Raman Spectra Calculation of Ordered-Vacancy Ga₂Se₃Compounds; Origin of Anisotropy