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Nearly stoichiometric thin films of CdGa2Se4 were deposited, by conventional thermal evaporation of presynthesized ingot material, onto quartz and Corning glass substrates. The chemical composition of the samples was determined by means of energy-dispersive X-ray spectrometry. X-ray diffraction studies revealed that the as-deposited and annealed films at Ta = 473 and 573 K have an amorphous phase, while those annealed at Ta ≥ 673 K are crystalline with a single phase of a defective chalcopyrite structure similar to that of the synthesized material. The unit cell lattice parameters of both the synthesized material and the crystalline films were determined and compared with reported data. The optical constants (n, k) and the film thickness (t) of the films were determined from optical transmittance data using the Swanepoel method. The dispersion parameters were determined from an analysis of the refractive index. An analysis of the optical absorption spectra revealed a non-direct energy gap characterizing the amorphous films, while a direct energy gap characterized the crystalline films. The annealing temperature dependence of the corresponding energy gaps was found to fit a polynomial equation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Polycrystalline ingot of AgGa0.5In0.5Te2 was synthesized. Thin films of AgGa0.5In0.5Te2 were prepared by thermal evaporation of the prereacted material on Corning glass substrates. Chemical composition of the starting material as well as thin films has been revealed that they are nearly stoichiometric. The crystal structure and the unit cell lattice parameters of both the starting material and thin films were determined from X-ray diffraction (XRD) studies. It has been revelead that the as-deposited and annealed films at 373, 423 K are amorphous, while those annealed at 473 and 523 K are polycrystalline with single-phase of a tetragonal chalcopyrite structure as that of bulk material. The optical absorption, of the annealed films at 523 K, was determined from the optical transmittance data. Three characteristics energy gaps of 1.142, 1.213 and 1.907 eV were obtained from an analysis of the optical absorption spectrum. The band structure of AgGa0.5In0.5Te2 at the center of the Brillouin zone was investigated and the d-like character was determined to be 19.87%. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thin films of CuxAg1–xInTe2 solid solutions (x = 0.25, 0.50 and 0.75) were deposited by thermal evaporation of prereacted materials on glass substrates. X-ray diffraction (XRD) studies has revealed that the as-deposited and thermally annealed films are polycrystalline with single-phase of a tetragonal chalcopyrite structure as that of bulk material with (112) predominant reflecting plane. The films compositions were confirmed by using energy dispersive analysis of X-rays (EDAX). The refractive index, n, and the extinction coefficient, k, of the annealed films with different compositions were determined in the spectral range, 400–2500 nm. Three characteristic energy gaps have been determined from the analysis of optical absorption spectrum for each composition. The three energy gaps are attributed to the optical transitions from the valence sub-bands to the conduction band minimum. Besides, a fourth energy gap has also been obtained for each composition, which may be attributed to the transition from the copper 3d-level to the conduction band minimum. However, the band gaps showed linear variation with the value of x.