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    CBD grown ZnO nanostructures: effects of solution temperature
    (Carl Hanser Verlag, 2013) Kahraman, Suleyman; Cakmak, Haci Mustafa; Cetinkaya, Samed; Cetinkara, Haci Ali; Guder, Husnu Salih
    In the present study, textured and highly oriented nano-structured ZnO films were synthesized via chemical bath deposition. The effects of solution temperature have been investigated. It is concluded that the solution temperature is crucial to the crystallography, morphology, electrical and optical behaviors of the ZnO films. X-ray diffraction studies and scanning electron microscopy observations revealed that the structures grown at 95 degrees C had a large aspect ratio, a faster c-axis growth and better vertical orientation than those obtained at relatively lower temperature. The variations depending on solution temperature have been provisionally explained theoretically. Electrical resistivity and activation energies of the films decreased with increasing solution temperature. The variation was attributed to enhancement in the crystallographic structure with increasing growth temperature and to delocalized phonon states. Through the optical absorption spectra a red shift was observed and attributed to crystal defects, non-stochiometry that Zn+2 ions substitute oxygen vacancies and delocalized phonon states.
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    Cu2SnS3 absorber thin films prepared via successive ionic layer adsorption and reaction method
    (Carl Hanser Verlag, 2013) Kahraman, Suleyman; Cetinkaya, Samed; Cakmak, Haci Mustafa; Cetinkara, Haci Ali; Guder, Husnu Salih
    In this paper, we report the production of Cu2SnS3 thin films with high phase purity via successive ionic layer adsorption and reaction method on soda lime glass substrates. Structural, morphological, compositional, optical and electrical investigations were carried out. The X-ray diffraction patterns of the samples matched very well with the reference pattern and proved the polycrystalline nature of the films. As a secondary phase, one weak peak indicating covallite Cu2-xS phase was observed in the pattern of the sample deposited by using equimolar Cu and Sn. The surface morphologies of the films were found to be continuous and composed of homogeneously distributed large grains. From the reflectance and transmittance data, the optical absorption coefficient values of the films were found to be about 10(4) cm(-1) and the films were found to be almost opaque in the wavelengths from 200 to 600 nm with a small reflectivity of about 10%. Band gap values of the films decreased from 1.45 to 1.35 eV with decreasing Cu content. Electrical characterization showed that the films were p-type semiconductor. Two different impurity levels for each film were found via resistivity-temperature characteristics.