The results of experimental and theoretical studies of the optical-energy properties of CdS thin films are reported. The synthesis procedure and the results of structural and optical studies...

The optical constants and thickness of CdSe thin films prepared by quasi close-space sublimation method are determined. The structural investigations performed by means of XRD technique showed that the films have a polycrystalline and hexagonal structure. The optical constants and the band gap of the films under study have been determined (E_g= 1.68 eV). Optical properties (refractive index n(λ), absorption coefficient α(λ), and extinction coefficient k(λ)) of thin films and thickness d can be determined from the transmission spectrum. The dispersion of the refractive index was explained using a single oscillator model. Single oscillator energy and dispersion energy are obtained from fitting. Optical parameters of the films were determined using the Cauchy, Sellmeier and Wemple models.

We investigate an influence of the crystal structure imperfections on the electronic properties and dielectric functions of the In_0.5Tl_0.5I semiconductor in the frame of the density functional theory calculations. The tensor of electron effective mass \( m^{*}_{ij} \) for the InI, In_0.5Tl_0.5I and TlI crystals has been calculated for the valence and conduction bands at different K-points of the Brillouin zone. The dielectric functions ε(hν) of the imperfect crystals based on In_0.5Tl_0.5I solid state solution with iodine vacancy and a thallium interstitial atom were calculated taking into consideration the inter-band and intra-band electron transitions. The studies of the imperfect crystals reveal increased low-frequency and stationary electron conductivity with anisotropy resulted from the anisotropy of the electron effective mass tensor. Our findings explain the origin of crucial changes in the band structure by formation of the donor half-occupied levels close to the unoccupied conduction bands due to the crystal structure defects, i.e., iodine vacancy or a thallium interstitial atom. It has been shown that in the case of real crystals, in particular metal-halides, the proper consideration of defects in quantum-chemical calculations results in a better matching with experimental data and, opposite to the perfect structure calculations, gives opportunities to explain the observed phenomena.

Journal of Nano- and Electronic Physics. Scientific journal. ISSN: 2077-6772. Journal abbreviation: J. Nano- Electron. Phys. No page charges. All articles are freely available on-line. Issued 4 times per year. Publisher: Sumy State University. (Sumy, Ukraine)