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Journal ArticleDOI

Optical absorption and electrical conductivity of flash evaporated CuGaTe2 thin films

01 Mar 1986-Pramana (Springer Science and Business Media LLC)-Vol. 26, Iss: 3, pp 269-276
TL;DR: In this article, the optical absorption edge of CuGaTe2 thin films in the energy range 1 to 2·3 eV was studied and the characteristic band gaps were found to be 1·23 eV and 1·28 eV whereas the acceptor ionization energy was 170 meV.
Abstract: The optical absorption edge of CuGaTe2 thin films in the energy range 1 to 2·3 eV was studied. The characteristic band gaps were found to be 1·23 eV and 1·28 eV whereas the acceptor ionization energy was 170 meV. Electrical conductivity measurements were carried out in the temperature range 300–550 K and two acceptor states with ionization energies 400 meV and 140 meV were found. The origin of acceptor states is explained based on covalent model.
Citations
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Journal ArticleDOI
TL;DR: It is shown that through alloying of isoelectronic elements In and Ag in CuGaTe2 , a quinary alloy compound system Cu1- x Agx Ga0.4 In0.6 Te2 with complex nanosized strain domain structure can effectively suppress its thermal conductivity and elevate its thermoelectric performance remarkably.
Abstract: Chalcopyrite compound CuGaTe2 is the focus of much research interest due to its high power factor. However, its high intrinsic lattice thermal conductivity seriously impedes the promotion of its thermoelectric performance. Here, it is shown that through alloying of isoelectronic elements In and Ag in CuGaTe2 , a quinary alloy compound system Cu1-x Agx Ga0.4 In0.6 Te2 (0 ≤ x ≤ 0.4) with complex nanosized strain domain structure is prepared. Due to strong phonon scattering mainly by this domain structure, thermal conductivity (at 300 K) drops from 6.1 W m-1 K-1 for the host compound to 1.5 W m-1 K-1 for the sample with x = 0.4. As a result, the optimized chalcopyrite sample Cu0.7 Ag0.3 Ga0.4 In0.6 Te2 presents an outstanding performance, with record-high figure of merit (ZT) reaching 1.64 (at 873 K) and average ZT reaching 0.73 (between ≈300 and 873 K), which are ≈37 and ≈35% larger than the corresponding values for pristine CuGaTe2 , respectively, demonstrating that such domain structure arising from isoelectronic multielement alloying in chalcopyrite compound can effectively suppress its thermal conductivity and elevate its thermoelectric performance remarkably.

50 citations

Journal ArticleDOI
TL;DR: In this article, thin films of CuGaTe2 with thickness in the range, 0.1-1.0 μm were deposited on Corning 7059 glass substrates by flash evaporation.

44 citations

Journal ArticleDOI
TL;DR: In this paper, a polycrystalline and single-phase CuGaTe2 thin films were prepared by flashevaporation of the pre-reacted material, synthesized from its constituent elements.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of substrate temperature (T s ) on the electrical characteristics of thin films of 0.7 μm thickness was studied and the electrical resistivity was found to decrease with film thickness, whereas the mobility increased.

2 citations

Journal ArticleDOI
TL;DR: In this article , a planetary ball milling of the source element powders (Cu, Al, Ga, and Te) was used to produce polycrystalline semiconductors with a tetragonal chalcopyrite structure with (1 1 2) orientation.
Abstract: The CuAlxGa1−xTe2 powders used in this study were made by planetary ball milling the source element powders (Cu, Al, Ga and Te). All of the produced powders and thin films were polycrystalline, with a tetragonal chalcopyrite structure with (1 1 2) orientation, according to XRD analysis. The structural and electronic features of the CuAlxGa1−xTe2 semiconductors were predicted using ab initio calculations based on Density Function Theory (DFT). The acquired results demonstrated that once the Al concentration increased, the lattice parameters and energy band gap changed in a way that was consistent with the experimental data.
References
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Journal ArticleDOI
W. Hörig1, H. Neumann1, H. Sobotta1, B. Schumann, G. Kühn 
TL;DR: In this article, the optical absorption in flash-evaporated CuInSe 2 thin films was studied in the photon energy range from 1 to about 3 eV, and it was shown that at energies well above the edge there exists an additional optical absorption due to forbidden direct transitions with the same characteristic gap energy.

163 citations

Journal ArticleDOI
H. Neumann1, W. Hörig1, E. Reccius1, H. Sobotta1, B. Schumann, G. Kühn 
TL;DR: In this paper, a model for the band structure of CuGaTe2 near the point Γ of the Brillouin zone was proposed and three transverse optical mode frequencies were obtained from an analysis of the optical transmission spectra in the photon energy range from 1 to about 3 eV.

129 citations

Journal ArticleDOI
H. Neumann1
TL;DR: The electrical properties of all AIBIIIC compounds can be interpreted in a consistent manner if the electrical activity (donor or acceptor) of the intrinsic defects is considered in the covalent bonding model as mentioned in this paper.
Abstract: The electrical parameters of undoped melt grown AIBIIICVI2 crystals are compared with predictions which can made considering the deviations from stoichiometry due to the incongruent evaporation of these compounds. It is shown that the electrical properties of all AIBIIIC compounds can be interpreted in a consistent manner if the electrical activity (donor or acceptor) of the intrinsic defects is considered in the covalent bonding model. Die elektrischen Parameter undotierter, aus der Schmelze gezuchteter AIBIIIC-Kristalle werden mit den Voraussagen verglichen, die sich aus einer Betrachtung der durch die inkongruente Verdampfung bedingten Stochiometrieabweichungen ergeben. Es wird gezeigt, das eine widerspruchsfreie Interpretation der elektrischen Eigenschaften aller AIBIIIC-Verbindungen moglich ist, wenn die elektrische Wirkung (Donator oder Akzeptor) der Eigendefekte im Modell der kovalenten Bindung betrachtet wird.

82 citations

Journal ArticleDOI
TL;DR: In this paper, the resistivity and Hall coefficient for undoped p-type CuGaS2 were measured at temperatures between 77 and 400°K, where the acceptor ionization energy increased from 0.073 to 0.39 eV with the decrease of acceptor concentration.
Abstract: The resistivity and Hall coefficient for undoped p‐type CuGaS2 were measured at temperatures between 77 and 400°K. The crystals were grown from both the stoichiometric melt and the vapor phase. The crystals were heat treated under an excess sulfur atmosphere in the temperature range 400–660°C. An analysis of the hole concentration data showed that the heat treatment changed the acceptor concentration from 6×1014 to 2×1018 cm−3. The acceptor ionization energy increased from 0.073 to 0.39 eV with the decrease of the acceptor concentration. The effective mass of the hole in CuGaS2 from the Hall analysis was ∼0.69me. The formation energy of the Cu vacancy, which is presumably an intrinsic acceptor, was ∼0.68 eV in CuGaS2. The acceptor energy of the Cu vacancy in the lower concentration limit was ∼0.12 eV. The mobility shows the dominance of lattice scattering through a deformation potential at higher temperatures than 110°K, while the observed mobility data at lower temperatures can be reasonably explained by taking into account the effect of space‐charge scattering.

66 citations