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Öğe Alloying and phase transformation in CdS/CdSe bilayers annealed with or without CdCl2(Elsevier Sci Ltd, 2019) Ciris, A.; Basol, B. M.; Yilmaz, S.; Atasoy, Y.; Tomakin, M.; Kucukomeroglu, T.; Bacaksiz, E.The present paper studies the structural, compositional, morphological and optical properties of thin CdS/CdSe stacks annealed in an inert atmosphere or subjected to a CdCl2 treatment. The bilayer stacks were fabricated by chemical bath deposition (CBD) of a 50 nm thick CdS layer followed by evaporation of a CdSe film with equal thickness. It was found that when this stack was annealed at 400 degrees C for up to 10 min, no appreciable intermixing/alloying between the two layers was detected. Upon heating for 5-10 min in presence of a CdCl2 layer disposed over the CdSe film, however, led to appreciable alloying and formation of CdSSe, which was confirmed through XRD, optical transmission and room temperature photoluminescence measurements. XRD data further showed that the CdS layer in the CdS/CdSe stack had nano-amorphous structure that did not change upon annealing in inert atmosphere. The CdSe layer of the stack, which had a cubic structure, also preserved its phase upon annealing in inert atmosphere. When the CdS/CdSe stack was CdCl2 treated, the phase of the CdSSe alloy formed was transformed to hexagonal. These observations may have consequences in applications where CdS/CdSe bilayers are formed within device structures and subjected to various types of heat treatments.Öğe Comparative studies of CdS, CdS:Al, CdS:Na and CdS:(Al-Na) thin films prepared by spray pyrolysis(Academic Press Ltd- Elsevier Science Ltd, 2015) Yilmaz, S.; Atasoy, Y.; Tomakin, M.; Bacaksiz, E.In the present study, the spray pyrolysis technique was used to prepare pure CdS, 4 at.% Al-doped CdS, 4 at.% Na-doped CdS and (4 at.% Al, 4 at.% Na)-co-doped CdS thin films. It was found from X-ray diffraction data that all the specimens showed hexagonal wurtzite structure with the preferred orientation of (101). Scanning electron microscopy results indicated that 4 at.% Al-doping caused a grain growth in the morphology of CdS thin films whereas the 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping led to porous structure with small grains. The band gap value of CdS thin films increased to 2.42 eV after 4 at.% Al-doping. However, it reduced to 2.30 eV and 2.08 eV for 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping, respectively. The room temperature photoluminescence measurements illustrated that the peak intensity of CdS thin films enhanced with 4 at.% Al-doping while 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping caused a decline in the intensity. The maximum carrier concentration and minimum resistivity were obtained for 4 at.% Al-doped CdS thin films, which is associated with the grain growth. Furthermore, (4 at.% Al, 4 at.% Na)-co-doping gave rise to a slight reduction in the carrier concentration and a slight increment in the resistivity. As a result, it can be said that 4 at.% Al-doped CdS thin films exhibited the best electrical and optical properties, which is important for the optoelectronic applications. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Structural, morphological, optical and electrical evolution of spray deposited ZnO rods co-doped with indium and sulphur atoms(Springer, 2014) Yilmaz, S.; Polat, I.; Atasoy, Y.; Bacaksiz, E.Undoped and (In-S) co-doped ZnO films were grown by the spray pyrolysis method on glass substrates. The structural, morphological, optical and electrical properties of all the samples were studied in detail. X-ray diffraction results showed that all the samples have a hexagonal wurtzite structure with the preferred orientation that changed from (002) to the random orientation after (In-S) co-doping. From the scanning electron microscopy analysis, it is noted that the morphology of ZnO changed from rods to thin film upon (In-S) co-doping. Compared to undoped ZnO rods, transparency of (In-S) co-doped ZnO thin films significantly increased whereas their band gap values gradually decreased. From photoluminescence measurements, it is observed that the UV peak completely quenched after (In-S) co-doping while the deep level band intensity slightly increased especially for 2 and 4 at.% (In, S) co-doped ZnO samples. Compared with undoped sample, the carrier concentration enhanced with the increase of (In-S) co-doping to 4 at.% and further increase in the co-doping amount results in the decline of the conductivity.Öğe Synthesis and fabrication of Mg-doped ZnO-based dye-sensitized solar cells (vol 25, pg 3173, 2014)(Springer, 2014) Polat, I.; Yilmaz, S.; Bacaksiz, E.; Atasoy, Y.; Tomakin, M.[Abstract Not Available]Öğe Synthesis and fabrication of Mg-doped ZnO-based dye-synthesized solar cells(Springer, 2014) Polat, I.; Yilmaz, S.; Bacaksiz, E.; Atasoy, Y.; Tomakin, M.Undoped and 2, 4 and 6 at.% Mg-doped ZnO nanorods were successfully deposited on ZnO seeded fluorine tin oxide substrates by a simple chemical bath deposition technique to form a photoanode. It was seen that all the samples had a hexagonal wurtzite structure with compact rod morphology. From Tauc's plot results, as compared to the undoped one (3.26 eV), the optical band gap of the ZnO:Mg samples increased to 3.32 eV for 4 at.% Mg-doping concentration and then decreased to 3.27 eV for 6 at.% Mg-doping. Photoluminescence results measured at 300 K indicated that ZnO nanorods had a ultra-violet peak with a wavelength of 382 nm, a blue peak at 420 nm and a deep level band in the range of 450-800 nm. Undoped and Mg-doped ZnO nanorods were subsequently used to realize ZnO-based dye-synthesized solar cells which exhibited the best power conversion efficiency of 0.144 % for 4 at.% ZnO:Mg sample.
