Structural , D.C , and A.C. Mechanism for thermally evaporated CdXSe1-X thin films

This thesis was including study the effect of different concentration (X=0.1,0.2,0.3,and 0.4), thickness, t (200-500)nm ,and substrate temperature ,Ts (300-393)K on the structural and electrical properties for
CdXSe1-X thin films ,which prepared by thermal evaporation on glass substrate under vacuum of (2 ×10-5 mbar), and studying the mechanism of transition for the d.c conductivity and a.c conductivity. CdXSe1-X alloys for different (X) was prepared inside quartz vacuum tube; then heated to melting point and left for five hours to get homogenous compound and then allowed to cool slowly to room temperature. From X-ray diffraction spectrum appeared that all alloys have polycrystalline structure with hexagonal Wurtzite phase at (X=0.2) and mixture phase of hexagonal and cubic at (X=0.1,0.3,0.4). XRD results shows that all CdXSe1-X films for thickness (400 nm) at (Ts=300 K) are polycrystalline with mixture of hexagonal and cubic phase at (X=0.1,0.3,0.4), while the other films at (X=0.2) at the same condition are polycrystalline with cubic structure and the preferred orientation is (111), also it has been found that the structure of the film at (X=0.3), and at room temperature (Ts=300 K) with different thicknesses are polycrystalline with mixture structure a hexagonal and cubic phase and the preferred orientation is (111), but at the same concentration (X=0.3) at thickness (400 nm) with different substrate temperature the films are polycrystalline with hexagonal and cubic structure, and the concentration of Se increases with substrate temperature increasing. D.C. conductivity showed irregular behavior with increasing concentration (X), but it's increases with the increase in thickness (t), while decrease when increase substrate temperature, and all films have two activation energy. From studying the variation of A.C. conductivity and the exponent factor (s) with angular frequency and temperature, we founded that the correlated barrier hopping (CBH) is a suitable model to explain
experimental result, also by use the Cole-Cole diagram we calculated relaxation time (t),(t D) for ideal and non ideal Debye model respectively , polarization (a), and the static dielectric constant (es) and we found that the static dielectric constant increasing from 3.7 to 28 with increasing the substrate temperature from 300 K to 393 K, but the relaxation time decreasing with increasing the substrate temperature. Hall measurements confirmed that all the films are (p-type).