Generally the a.c. conductivity shows a power law in frequency s  ()  where the exponent s ≤ 1. As the frequency goes to zero the conductivity become frequency independent. The a.c. conductivity was studied for the Ge1-xSex thin films to see how the selenium contents affect the permittivity and the permeability for the Ge1-x Sex. The thin films prepared by thermal evaporation at room temperature and under vacuum (~2 x10-5toor) using Edward coating unit model 306A. From the relation between ln conductivity and ln w, the effect of selenium contents in Ge1-x Sex thin films on the exponent value, the relaxation time and the maximum barrier height. An algebric fitting method for circles and circular arcs was used to find the permit

SnO2 thin films of different two thicknesses were prepared an glass substrate by DC magnetron sputtering. The crystal structure and orientation of the films were investigated by XRD patterns. All the deposited films are polycrystalline. The grain size was calculated as 25.35, 28.8 nm. Morphological and compositions of the films were performed by SEM and EDX analyses respectively. The films appeared compact and rougher surface in nature. The allowed direct band gap was evaluated as 3.85 eV, and other optical constants such as refractive index, extinction coefficient, real and imaginary parts of dielectric constants were determined from transmittance spectrum in the wavelength range (300-900) nm and also analyzed.
 

Spin coating technique used to prepare ZnPc, CdS and ZnPc/CdS blend thin films, these films annealed at 423K for 1h, 2h and 3h. Optical behavior of these films were examined using UV-Vis. and PL. The absorption spectrum of ZnPc shows a decreasing in absorption with the increase of annealing time while CdS spectrum give a clearly absorption peak at~510 nm. Energy gap of ZnPc increases from 1.41 to 1.52 eV by increasing the annealing time. E_g of CdS decrease by increasing annealing time, from 2.3 eV to 2.2 eV. The intensities of the peaks obtained from PL spectra were strongly dependent on annealing time and confirmed the results obtained from UV-Vis. D.C. conductivity measurement showed that all the thin films have two differen

Polyaniline (PANI) and Ag/PANI nanocomposite thin films have prepared by microwave induced plasma. The Ag powder of average particle size of 50 nm, were used to prepare Ag/PANI nanocomposite thin films. The Ag/PANI nanocomposite thin films prepared by polymerization in plasma and characterized by UV-VIS, FTIR, AFM and SEM to study the effect of silver nanoparticles on the optical properties, morphology and structure of the thin films. The optical properties studies showed that the energy band gap of the Ag/PANI (5%wt silver) decreased from 3.6 to 3.2 eV, where the substrate location varied from 4.4 to 3.4 cm from the axis of the cylindrical plasma chamber. Also the optical energy gap decreased systematically from 3.3 to 3 eV with increas

 X-ray diffraction pattern reveled the tetragonal crystal system of SnO2  Thin films of SnO2 were prepared on glass substrates using Spray Pyrolysis Technique. The absorption and transmition spectra were recorded in the rang of 300-900nm,  the   spectral   dependences   of   absorption coefficient were calculated   from   transmission spectra. The direct and allowed optical  energy gap has been evaluated from plots of   (αhÏ…)²  vs. (hÏ…) . The energy gap was found to be  2.4-2.6eV.  The optical constant such as extinction coefficient( k )  and absorption coefficient ( α) have been evaluated. 

Zinc Oxide (ZnO) is considered as one of the best materials already used as a window layer in solar cells due to its antireflective capability. The ZnO/MgF2 bilayer thin film is more efficient as antireflective coating. In this work, ZnO and ZnO/MgF2 thin films were deposited on glass substrate using pulsed laser deposition and thermal evaporation deposition methods. The optical measurements indicated that ZnO thin layer has an energy gap of (3.02 eV) while ZnO/MgF2 bilayer gives rise to an increase in the energy gap. ZnO/MgF2 bilayer shows a high energy gap (3.77 eV) with low reflectance (1.1-10 %) and refractive index (1.9) leading to high transmittance, this bilayer could be a good candidate optical material to improve the performance

     CuAlTe₂ thin films were evaporation on glass substrates using the technique of thermal evaporation at different range of thickness (200,300,400and500) ±2nm. The structures of these films were investigated by X-ray diffraction method; showing that films possess a good crystalline in tetragonal structure. AFM showed that the grain size increased from (70.55-99.40) nm and the roughness increased from (2.08-3.65) nm by increasing the thickness from (200-500) nm. The optical properties measurements, such as absorbance, transmtance, reflectance, and optical constant as a function of wavelength showed that the direct energy gap decreased from (2.4-2.34) eV by the gain of the thickness.

Structural, optical, and electrical properties of thin films of CdS : Zn prepared by the solution – growth technique are reported as a function of zinc concentration. CdS are window layers influencing the photovoltaic response of CIS solar cells. The zinc doping concentration was varied from 0.05 to 0.5 wt %, zinc doping apparently increase the band gap and lowers the resistivity. All beneficial optical properties of chemically deposited CdS thin films for application as window material in heterojunction optoelectronic devices are retained. Heat treatment in air at 400 °C for 1h modify crystalline structure, optical, and electrical properties of solution growth deposited CdS : Zn films.

(Sb₂S₃)_1-xSn_x thin films with different concentrations (0, 0.05 and
0.15) and thicknesses (300,500 and 700nm) have been deposited by
single source vacuum thermal evaporation onto glass substrates at
ambient temperature to study the effect of tin content, thickness and
on its structural morphology, and electrical properties. AFM study
revealed that microstructure parameters such as crystallite size, and
roughness found to depend upon deposition conditions. The DC
conductivity of the vacuum evaporated (Sb₂S₃)_1-x Sn_x thin films was
measured in the temperature range (293-473)K and was found to
increase on order of magnitude with