Yazar "Guder, Husnu Salih" seçeneğine göre listele

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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.
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    Facile Synthesis of Cu2ZnSnS4 Photovoltaic Absorber Thin Films via Sulfurization of Cu2SnS3/ZnS Layers
    (Springer, 2014) Kahraman, Suleyman; Podlogar, Mateja; Bernik, Slavko; Guder, Husnu Salih
    Copper zinc tin sulfide (Cu2ZnSnS4) has been receiving a lot of attention in recent years as a new, alternative absorber for the production of cheap thin film solar cells owing to the high natural abundance of all the constituents, its tunable direct-band-gap energy, and its large optical absorption coefficient. In addition, to overcome the problem of expensive vacuum-based methods, solution-based approaches are being developed for Cu2ZnSnS4 deposition. In this study, Cu2ZnSnS4 thin films were grown on soda lime glass substrates via the sulfurization of solution grown Cu2SnS3/ZnS stacked sulfide layers. A new facile route to overcome the difficulty of depositing Cu2ZnSnS4 thin film with a desired stoichiometric composition in a single cation solution has been presented. The influences of deposition cycles of layers on the morphological, compositional, structural, and optical properties of the samples were investigated. It was observed from scanning electron microscopy (SEM) images that the films were continuous and composed of homogenously distributed large grains. Possible chemical formulations of the best samples were predicted to be Cu1.99Zn1.25Sn1.00S3.76 and Cu1.97Zn1.03Sn1.29S3.71 via energy-dispersive X-ray spectroscopy (EDXS) results. The X-ray diffraction (XRD) patterns of the samples matched very well with the reference values. The Raman-scattering analysis of the films proved the phase purity of the CZTS samples. The optical absorption coefficient of the films was found to be about 10(4) cm(-1) based on absorbance spectroscopy. The optical band gaps of the films were estimated to be between 1.36 and 1.50 eV. From these we are able to conclude that CZTS thin films can be effectively obtained via the vacuum-atmosphere sulfurization of Cu2SnS3/ZnS stacked sulfide layers. (C) The Minerals, Metals & Materials Society and ASM International 2013