Structure modifications in chalcopyrite semiconductors (original) (raw)
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Effect of Na substitution on electronic and optical properties of CuInS2 chalcopyrite semiconductor
Journal of Solid State Chemistry, 2015
We observe significant effects of structural distortion on electronic and optical properties of CdGa 2 X 4 (X = S, Se, Te) defect chalcopyrite. The calculation is carried out within Density functional theory based tight binding linear muffin tin orbital (TB-LMTO) method. Structural parameters and band gap of CdGa 2 X 4 agree well with the available experimental values within LDA limit. Change in band gap due to structural distortion is 3.63%, 4.0%, and 8.8% respectively. We observe significant change in optical properties also due to this effect. Effects on optical properties come mainly from optical matrix elements. Our results of these response functions agree well with the available experimental values.
Journal of Physics: Conference Series, 2019
The current work reports the synthesis and characterization of a photovoltaic material based on the CuIn1−xGaXSe2(X = 0.3 y 0.5) system, making use of the doctor blade method. For this purpose, homogeneous inks were obtained and worked under previous stoichiometry arrangement. The deposition process of thin films, were made in a heating plate on conventional glass substrates, previously washed and treated for this purpose. Once the layers of Cu, In, and Ga were deposited by chemical bath, a thermal treatment was performed at 550 °C for 30 min in a conditioned oven, in which the selenization process was performed. The obtained films were characterized by X-ray diffraction, Raman spectroscopy, solid-state impedance spectroscopy, UV spectroscopy and scanning electron microscopy techniques. The identification of the main crystalline phase could be corroborated, as well as the conductive and optoelectronic behavior of the solids in accordance with reported in literature. Simultaneously, ...
Electronic properties of chalcopyrite CuAlX 2(X=S,Se,Te) compounds
Solid State Communications, 2008
We present results of the band structure and density of states for the chalcopyrite compounds CuAlX 2 (X = S, Se, Te) using the state-of-the-art full potential linear augmented plane wave (FP-LAPW) method. Our calculations show that these compounds are direct band gap semiconductors. The energy gap decreases when S is replaced by Se and Se replaced by Te in agreement with the experimental data. The values of our calculated energy gaps are closer to the experimental data than the previous calculations. The electronic structure of the upper valence band is dominated by the Cu-d and X-p interactions. The existence of Cu-d states in the upper valence band has significant effect on the optical band gap.
Defect physics of the CuInSe2 chalcopyrite semiconductor
Journal of Physics and Chemistry of Solids, 1999
The activation energies of acceptor E A and donor levels E D in the chalcopyrite compound CuInSe 2 are calculated by using a simpler model based in the effective-mass theory for the case of single, double and triple point defect centers. Despite of the simplicity of this model, it is found that the values of E A and E D thus calculated for shallow and deep levels are in reasonable agreement with those reported from the experimental data. In the case of not shallow donor levels values of E D in good agreement with these data are calculated by using the free electron mass m 0 instead of the effective electron mass. From the analysis of the results, most of these levels have been identified as due to the presence of several native point defects.
Influence of secondary phase Cu[sub x]Se on the optoelectronic quality of chalcopyrite thin films
Applied Physics Letters, 2011
The effect of secondary phase Cu x Se on the absorber quality of epitaxial CuGaSe 2 films is studied by spatially resolved photoluminescence combined with scanning electron microscopy. We show that the presence of Cu x Se crystals on the absorber during growth under Cu excess results in a locally increased crystal quality in the vicinity of the Cu x Se crystallites, affecting the defect structure of the absorber. This effect remains after removal of Cu x Se and induces a local reduction in the recombination centers, resulting in locally higher excess carrier concentrations and larger splitting of quasi-Fermi levels.
A mild solvothermal route to chalcopyrite quaternary semiconductor CuIn(SexS1 − x)2 nanocrystallites
Journal of Materials Chemistry, 2001
Chalcopyrite quaternary semiconductor CuIn(Se x S 12x ) 2 nanocrystallites (0¡x¡1) were successfully prepared via a relatively simple and convenient solvothermal route. From X-ray data it is found that the cell constants a and c vary linearly with the composition x as: a(Å )~5.5299z0.2665x, c(Å )~11.1004z0.5139x. The sample CuInSeS was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (IR). The optical property of CuIn(Se x S 12x ) 2 nanocrystallites was also recorded by means of UV-Vis absorption spectroscopy. In addition, the effect of different solvents on the formation of the product was studied to indicate that ethylenediamine is the optimal solvent for this reaction. Finally, the reaction mechanism in ethylenediamine was also investigated.
Vibrational and crystalline properties of polymorphic CuInC2 (C=Se,S) chalcogenides
Physical Review B, 2005
This paper deals with the analysis of the vibrational and crystallographic properties of CuInC 2 ͑C =S,Se͒ chalcogenides. Experimentally, evidence on the coexistence in epitaxial layers of domains with different crystalline order-corresponding to the equilibrium chalcopyrite ͑CH͒ and to CuAu ͑CA͒-has been obtained by cross section transmission electron microsopy ͑TEM͒ and high resolution TEM ͑HREM͒. Electron diffraction and HREM images give the crystalline relationship ͓110͔ CH ʈ ͓100͔ CA and ͑112͒ CH ʈ ͑011͒ CA , observing the existence of a ͑112͒ CH ʈ ͑001͒ CA interphase between different ordered domains. The vibrational properties of these polytypes have been investigated by Raman scattering. Raman scattering, in conjunction with XRD, has allowed identifying the presence of additional bands in the Raman spectra with vibrational modes of the CA ordered phase. In order to interpret these spectra, a valence field force model has been developed to calculate the zone-center vibrational modes of the CA structure for both CuInS 2 and CuInSe 2 compounds. The results of this calculation have led to the identification, in both cases, of the main additional band in the spectra with the total symmetric mode from the CuAu lattice. This identification is also supported by first-principles frozenphonon calculations. Finally, the defect structure at the interphase boundaries between different polymorphic domains has also been investigated.
Thin Solid Films, 2003
In this work the occurrence of two polytypic structures, chalcopyrite (CH) and cationic fcc CuAu-ordering (CA), in epitaxial CuInS samples on Si (1 1 1) oriented substrates has been studied. Samples with different Cu-to-In ratios and grown at 500 and 2 575 8C, respectively, have been analysed. Cross-section Transmission electron microscopy (TEM) samples have been prepared and studied in two directions normal to the growth direction w2 2 1x , namely, w1-1 0x , which is parallel to w1 0 0x , and CH CH CA w1 1-1x that is parallel to w0 1-1x . Electron diffraction and high resolution TEM images corroborate the existence of both CH CA polytypes and give the orientation relationship between them, namely, w1-1 0x NNw1 0 0x and (1 1 2) NN(0 1 1) . Cu-rich CH CA CH CA samples have good crystalline quality with large grains and sharp interfaces between both polytypes, the most important being between the (1 1 2) and (0 1 1) planes. On the contrary, the crystalline quality of Cu-poor samples is minor, no clear CH CA interfaces can be observed, and a high density of twins in the (0 1-1) planes can be observed. The results on the crystalline CA quality are in agreement with previous results on polycrystalline CuInS films.