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Öğe Bandgap variation of nanostructure tin doped CdO films via SILAR processing(Elsevier Sci Ltd, 2014) Sahin, B.; Taskopru, T.; Bayansal, F.Five series of pure and tin-doped CdO films have been grown on amorphous glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. The film's structural, morphological and optical properties have been investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and UV-vis spectrophotometer. XRD results showed that all of the films are polycrystalline cubic CdO. Doping of tin enhances the film's (111) preferred orientation and causes slight shift in the (111) Bragg angle towards higher value. From the FESEM images, it was seen that tin-doping concentration affects the shapes of the nanostructures. It was found that the tin-doping concentration modify the microstructures. With UV-vis analysis at the room temperature it was seen that the optical band gap and transmission properties of the films change with increasing tin concentration in the growth bath. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe Characterisation of ZnO nanorod arrays grown by a low temperature hydrothermal method(Taylor & Francis Ltd, 2012) Kahraman, S.; Cetinkara, H. A.; Bayansal, F.; Cakmak, H. M.; Guder, H. S.In this paper, growth steps of well defined ZnO nanorod arrays deposited on seeded substrates were investigated. To obtain ZnO seed layer on glass substrates, a successive ionic layer adsorption and reaction (SILAR) method was used and then ZnO nanorods were grown on seed layer using a chemical bath deposition (CBD) method. The effects of seed layer and deposition time on morphology, crystallographic structure (e.g. grain size, microstrain and dislocation density) and electrical characteristics of ZnO nanorods were studied. From the SEM micrographs, it could be seen that the ZnO nanorods densely covered the substrate and were nearly perpendicular to the substrate surface. The XRD patterns showed that the ZnO nanorod arrays had a hexagonal wurtzite structure with a preferred orientation along the (002) plane. An increase in deposition time resulted in an increase in the intensity of the preferred orientation and grain size, but a decrease in microstrain and dislocation density. Electrical activation energies of the structures were calculated as 0.15-0.85 eV from current-temperature characteristics. It was concluded that the morphologies of the structures obtained in this study via a simple and fast solution method can provide high surface areas which are important in area-dependent applications, such as solar cells, hydrogen conversion devices, sensors, etc.Öğe Characteristics of ZnO thin films doped by various elements(Elsevier Science Bv, 2013) Kahraman, S.; Cakmak, H. M.; Cetinkaya, S.; Bayansal, F.; Cetinkara, H. A.; Guder, H. S.We have investigated the effects of Al, K and Co dopant elements on the properties of ZnO thin films deposited by CBD method on glass substrates. Changing in morphology, structural parameters, ionization energies of impurity levels, absorption behavior and optical band gap values were investigated through scanning electron microscopy (SEM), X-Ray diffraction (XRD), resistance-temperature measurement (R-T) and ultraviolet-visible spectroscopy (UV-vis) techniques. From the SEM observations, various morphologies (rod-like, flower-like and rice-like) were observed. Those morphological variations were attributed to the change in stable growth mechanism of intrinsic ZnO, induced by different atomic radius and different electronegativity of dopants. XRD results indicated that all orientations are well indexed to hexagonal phase crystalline ZnO. The impurity level ionization energy values (Delta E) were estimated as 0.32/0.13/0.07 eV; 0.34/0.15 eV; 0.40/0.13 eV and 0.48/0.22 eV for the Al, K, Co doped samples and i-ZnO, respectively. Optical band gap values were found that the doped samples' were higher than the intrinsic one's. This increasing (blue shift) was attributed to a deterioration which occurred in the lattice of the structures after doping. This effect was also supported by the structural results. (C) 2012 Elsevier B.V. All rights reserved.Öğe Characterization of Al/n-ZnO/p-Si/Al structure with low-cost solution-grown ZnO layer(Taylor & Francis Ltd, 2013) Cetinkaya, S.; Cetinkara, H. A.; Kahraman, S.; Bayansal, F.We report the fabrication of Al/n-ZnO/p-Si/Al diode structures with a flower-like ZnO layer. The average grain size, microstrain and dislocation density in the ZnO layer were determined as 25nm, 1.55x10(-3) and 3.23x10(13)cm(-2), respectively. From absorption spectra, the optical band gap was found to be approximate to 3.17eV. A red shift was attributed to non-stoichiometry arising from Zn+2 ions substituting for oxygen vacancies. The ideality factor was determined as 1.55. The barrier height was calculated as 0.71eV from I-V characteristics and 0.73eV using the Norde plots.Öğe Characterization of CBD grown ZnO films with high c-axis orientation(Elsevier Science Sa, 2012) Kahraman, S.; Bayansal, F.; Cetinkara, H. A.; Cakmak, H. M.; Guder, H. S.Highly c-axis oriented ZnO films were deposited on seeded glass substrates. Successive ionic layer adsorption and reaction (SILAR) method and chemical bath deposition (CBD) method were used to obtain seed layers and ZnO films. To see the effects of seed layer and deposition time, structural (e.g. grain size, microstrain and dislocation density), morphological, and electrical (e.g. resistivity, activation energy) properties of the films were investigated by scanning electron microscopy, X-ray diffraction, and four point probe method. From the SEM images, resultant structures were found as well defined nanorods nearly perpendicular to the substrate surfaces and densely cover the substrates. The XRD patterns showed that ZnO films have hexagonal wurtzite structure with a preferred c-axis orientation along (002) plane. C-axis orientation was also supported by texture coefficient calculations. The lattice parameters of the structures were determined as a = 3.2268 angstrom, b = 5.2745 angstrom, alpha = beta = 90 degrees and gamma = 120 degrees. From the XRD patterns, it was revealed that, microstrain and dislocation density values of the structures decreased whereas grain size increased. This was attributed to enhancement occurred in lattice structure of the ZnO films. Activation energy values of the films were found in between 0.12 and 0.15 eV from the dark electrical resistivity-temperature characteristics in a temperature range of 300-500 K. (c) 2012 Elsevier B.V. All rights reserved.Öğe CuO nanostructures grown by the SILAR method: Influence of Pb-doping on the morphological, structural and optical properties(Elsevier Science Sa, 2015) Bayansal, F.; Gulen, Y.; Sahin, B.; Kahraman, S.; Cetinkara, H. A.CuO nanostructures with and without Pb were synthesized by the Successive Ionic Layer Adsorption and Reaction method. The films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and ultraviolet-visible spectrophotometry. Scanning electron microscopy results showed that the morphology of the film surface was changed from plate-like to coral-like nanostructures with increasing Pb concentration. The X-ray diffraction patterns showed the monoclinic crystal structure with preferential planes of ((1) over bar 11) and (111). Furthermore, ultraviolet-visible spectra showed that the band gap of the films was tailored by Pb doping. (C) 2014 Elsevier B.V. All rights reserved.Öğe Effect of coumarin concentration on the physical properties of CdO nanostructures(Elsevier Sci Ltd, 2014) Sahin, B.; Bayansal, F.; Yuksel, M.; Biyikli, N.; Cetinkara, H. A.In this work, nanostructured CdO films with different coumarin contents in the growth solution were fabricated on glass substrates by the HEAR method. The effects of coumarin content in the bath on optical, structural and morphological properties were studied by means of (UV-vis) spectrophotometer, SEM and XRD analysis. The analysis showed that the band gaps, surface morphologies and XRD peak intensities of the CdO films were found to change with coumarin content. A change in the band gap energy can be attributed to the improvement in crystallinity of the samples. XRD analysis showed that, the films have poly-crystalline structures with decent crystallinity levels. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe Effect of heat treatment on the properties of Cd(OH)2 and CdO films grown by chemical bath deposition(Taylor & Francis Ltd, 2013) Sahin, B.; Bayansal, F.; Cakmak, H. M.; Kahraman, S.; Cetinkara, H. A.Nanostructured cadmium hydroxide (Cd(OH)2) thin films have been fabricated on glass substrates by the chemical bath deposition method and converted into cadmium oxide (CdO) films by heat treatments. Some of the films were studied as-grown and the others were annealed in air at 150, 300 and 450 degrees C. The effects of various annealing processes on the structural, morphological and optical properties of the Cd(OH)2 and CdO films were studied. The band gaps of the films vary from 2.74eV to 2.32eV for different annealing temperatures. It was observed that there is a direct dependence of the structural, morphological and optical properties on the annealing temperature of the films. X-ray diffraction (XRD) measurements showed that as-grown and annealed film at 150 degrees C fully consist of Cd(OH)2 and the annealed films at 300 and 450 degrees C consist of CdO nanoparticles. The size of the nanoparticles, which were calculated from the scanning electron microscopy (SEM) figures by using a pixels program, was found to lie between 460 and 600nm.Öğe Effects of thermal oxidation temperature on vacuum evaporated tin dioxide film(Academic Press Ltd- Elsevier Science Ltd, 2012) Cakmak, H. M.; Cetinkara, H. A.; Kahraman, S.; Bayansal, F.; Tepe, M.; Guder, H. S.; Cipiloglu, M. A.In order to investigate the effect of thermal oxidation temperature on tin dioxide (SnO2), tin dioxide films were obtained on quartz substrates by vacuum evaporation of tin metal. The films were characterized by X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM), temperature dependent electrical resistivity measurement and optical absorption spectroscopy. The SEM images showed that the films are dense, continuous and are composed of nanoparticles and particle sizes are increased after thermal oxidation. From the X-ray measurement results, the films indicated two strong reflection peaks of tetragonal structure in the orientations of (101) and (200) at 20 = 33.8 degrees and 37.95 degrees, respectively. Intensity of the peaks increased with increasing thermal oxidation temperature. We found resistivity values of about 10(-4) Omega-cm. Optical absorption spectra of the films in the UV-Vis spectral range revealed that optical band gap (E-g) value of the films increases with increasing thermal oxidation temperature. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Fabrication and characterization of Mn-doped CuO thin films by the SILAR method(Elsevier Sci Ltd, 2013) Gulen, Y.; Bayansal, F.; Sahin, B.; Cetinkara, H. A.; Guder, H. S.Thin films of un-doped and Mn-doped CuO nanostructures have been deposited on glass substrates via the SILAR method. The morphological, compositional, structural and optical properties of the films have been investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction analysis and UV vis spectrophotometry. The analyzed results indicate that the obtained films consist of plate-like nanostructures. From the EDS analysis it is seen that Mn-doping concentration affects the shapes of the nanostructures. XRD results show that all of the films have monoclinic structure. From the room temperature UV-viS analysis it is found that the optical band gap of the films increases with increasing Mn-doping concentrations. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe Facile fabrication and characterization of SnxCu(1-x)O composite films by the SILAR method on glass substrates(Elsevier Science Sa, 2016) Bayansal, F.; Yuksel, M.; Sahin, B.CuO composite thin films with Sn-doping are deposited on glass substrates by the SILAR method. All the films are characterized by metallurgical microscopy, scanning electron microscopy, energy dispersive Xray spectroscopy, X-ray diffraction, UV-Vis. spectroscopy and Raman spectroscopy. Metallurgical microscopy and scanning electron microscopy results revealed that homogeneity of the film surface distorts and particle size decreases from 110 to 43 nm with increasing Sn-doping. Energy dispersive X-ray spectroscopy evidences the amount of Sn in CuO films, which increases with increasing Sn concentration in the growth solutions. X-ray diffraction patterns showed that the mean crystallite size of the films is decreasing from similar to 14 to similar to 9 nm with increasing Sn-doping. Moreover, increase in Sn concentration results new peaks belong to SnO2 phases. UV-Vis. analysis showed that the transmittance and optical band-gap energy values of the films are increasing with increasing Sn-doping. Raman spectrum was also confirmed the phase formation of CuO nanostructures and it was seen that the Sn-doping caused shifts in Raman active modes. (c) 2015 Elsevier B.V. All rights reserved.Öğe Facile synthesis of group-I elements (K, Li and Na)-doped nanostructured CdO films(Taylor & Francis Ltd, 2014) Sahin, B.; Bayansal, F.In this study, we report an application of facile and low-cost successive ionic layer adsorption and reaction method to investigate nanostructured CdO films. We have tried to enhance some physical properties of nanostructured CdO films by group-I (K, Li and Na) elements doping. The crystal structures, morphology, absorption, transmittance, reflectance behaviour and optical band gap values of CdO films were characterized by using X-ray diffraction (XRD), scanning electron microscopy and ultraviolet-visible spectroscopy techniques. XRD analysis reveals formation of CdO cubic crystalline structure. From these characterizations, it was seen that there are important distinctions in the structural, morphological and optical properties of undoped and K-, Li- and Na-doped nanostructured CdO films.Öğe Growth and Characterization of CuO Nanostructures on Si for the Fabrication of CuO/p-Si Schottky Diodes(Hindawi Publishing Corporation, 2013) Cetinkaya, S.; Cetinkara, H. A.; Bayansal, F.; Kahraman, S.CuO interlayers in the CuO/p-Si Schottky diodes were fabricated by using CBD and sol-gel methods. Deposited CuO layers were characterized by SEM and XRD techniques. From the SEM images, it was seen that the film grown by CBD method is denser than the film grown by sol-gel method. This result is compatible with XRD results which show that the crystallization in CBD method is higher than it is in sol-gel method. For the electrical investigations, current-voltage characteristics of the diodes have been studied at room temperature. Conventional I-V and Norde's methods were used in order to determine the ideality factor, barrier height, and series resistance values. It was seen that the morphological and structural analysis are compatible with the results of electrical investigations.Öğe Growth and humidity sensing properties of plate-like CuO nanostructures(Taylor & Francis Ltd, 2014) Bayansal, F.; Cetinkara, H. A.; Cankaya, G.This paper describes a simple, low-temperature and cost-effective liquid-phase method to synthesize homogenous plate-like CuO nanostructures and their sensitivity to humidity. Scanning electron microscopy illustrated that the synthesized CuO nanoplates have thicknesses of ~100 nm. X-ray diffraction measurements showed that the CuO nanostructures have high crystallinity with monoclinic crystal structure preferentially in and directions. From the temperature-dependant dark electrical resistivity measurements, the ionization energies of the impurity levels and thermal band gap energies of the films are found as 0.30, 0.32 and 1.37, 1.39 for as-synthesized and annealed films, respectively. Gas sensing characteristics of the films were investigated for different concentrations of humidity, isopropyl alcohol, methanol, ethanol, chloroform and acetone vapours. It was found that the sensor is sensitive to humidity but not to the other volatile organic compounds.Öğe Growth of homogenous CuO nano-structured thin films by a simple solution method(Elsevier Science Sa, 2011) Bayansal, F.; Kahraman, S.; Cankaya, G.; Cetinkara, H. A.; Guder, H. S.; Cakmak, H. M.This paper describes a simple, low temperature and cost effective solution method to synthesize homogenous cupric oxide (CuO) nano-structured thin films. By this method dense and continuous CuO films with good crystallinity can be prepared in a short time, e.g., in 15 min. The scanning electron microscopy illustrated that the synthesized CuO plate-like nanostructures have RMS thicknesses of 100 nm. The XRD measurements showed that the synthesized CuO nanostructures have a high crystallinity with monoclinic crystal structure preferentially in ((1) over bar 1 1) and (1 1 1) directions. From the temperature dependant dark electrical resistivity measurements the ionization energies of the impurity levels and thermal band gap energies of the films were calculated. (C) 2010 Elsevier B.V. All rights reserved.Öğe Influence of annealing to the properties of un-doped and Co-doped CdO films(Elsevier Sci Ltd, 2014) Sahin, B.; Bayansal, F.; Yuksel, M.; Cetinkara, H. A.Un-doped and Co-doped CdO nanostructures were deposited on glass substrates by successive ionic layer adsorption and reaction (SILAR) method and annealed at 300 and 400 C. Morphological, structural and optical properties of the films were investigated by scanning electron microscope (SEM), X-ray diffractometer (XRD) and ultra violet-vis (UV-vis) spectrophotometry. The analyzed results indicate that Co-doping concentration and annealing temperature affect the properties of nanostructure cadmium oxide (CdO) films. XRD results showed that all of the films are polycrystalline cubic CdO with good crystallinity levels. With UV-vis. analysis at the room temperature it was found that the doping and annealing temperature changed optical properties of CdO films. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Influence of coumarin as an additive on CuO nanostructures prepared by successive ionic layer adsorption and reaction (SILAR) method(Elsevier Science Sa, 2013) Bayansal, F.; Sahin, B.; Yuksel, M.; Biyikli, N.; Cetinkara, H. A.; Guder, H. S.The effect of coumarin doping during the growth of CuO nanostructures by SILAR method has been studied. It was found that coumarin consider ably influences the growth process, manipulates the band-gap and modifies the crystallite size of the films. XRD experiments evidenced that with higher coumarin concentrations in the growth solution, the microstrain and dislocation density increased, while the crystallite size of the films decreased. SEM images revealed that the thicknesses of the plate-like nanostructures decreased with increasing coumarin concentration. By UV/vis spectrophotometer analysis it is found that the coumarin concentration affects both the optical band gap and the transmission rate: both the band gap and spectral transmittance values of the films decreased for higher coumarin content. (C) 2013 Elsevier B. V. All rights reserved.Öğe Influence of manganese concentration and annealing temperatures on the physical properties of CdO films grown by the SILAR method(Taylor & Francis Ltd, 2014) Sahin, B.; Bayansal, F.; Yuksel, M.Undoped and doped Cadmium oxide (CdO) films with different Mn concentrations were prepared on glass substrates by the successive ionic layer adsorption and reaction method and annealed at two different temperatures. Structural, morphological and optical conditions were performed by XRD, scanning electron microscope (SEM) and UV-vis spectrum measurements. The deposited films were dense and they adhere well to the glass substrates. From the SEM photographs, it was seen that Mn doping concentration and annealing process affect the morphologies of the nanostructures. It was found that the growth process modifies the microstructures of the CdO films. XRD results and UV-vis analysis reveal that the crystal structure and optical band gap of the films could be adjusted by varying the Mn concentration and annealing temperature. The results also indicate that there is a direct dependence of the physical and optical properties of the metal oxide films on doping concentration and annealing process.Öğe Mechanical and structural properties of Li-doped CuO thin films deposited by the Successive Ionic Layer Adsorption and Reaction method(Elsevier Science Sa, 2020) Bayansal, F.; Sahin, O.; Cetinkara, H. A.Lithium-doped CuO thin films with different concentrations are deposited by the Successive Ionic Layer Adsorption and Reaction technique on glass substrates. The films are characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, UV-Vis. Spectroscopy, nanoindentation and in-situ scanning probe microscopy. Scanning electron microscopy showed uniform film surface and smaller particle size with increasing Li concentration. X-ray diffraction patterns revealed decreasing crystallite size with increasing Li concentration. The Raman spectra revealed CuO phases and a secondary phase of Cu2O at high doping concentrations especially after the concentration of 1.0 at.% Li. UV-Vis. Spectroscopy results indicated that the transmittance and bandgap values could be modified with Li-doping. Both of them are found to be increasing with increasing Li concentration. All indentation test load curves exhibited a smooth shape without any detected pop-in. The results of the nanoindentation test revealed that the nanohardness and elastic modulus increased with Li-doping.Öğe Modification of morphological, structural and optical properties of SILAR-based growth of CuO films on glass-slides by addition of dextrin(Elsevier Science Sa, 2014) Bayansal, F.; Sahin, B.; Yuksel, M.; Cetinkara, H. A.This paper presents the effect of dextrin addition to the growth solution to prepare CuO nanostructures by SILAR method. Structural, morphological and optical properties of the films were investigated by means of XRD, SEM and UV/Vis. analysis. From the XRD data it is found that with increasing dextrin concentrations in the growth solution the crystallite size of the films decreased. SEM images showed that dextrin addition has a decreasing effect on grain size and changes the morphology drastically. By UV/Vis spectrophotometer analysis it is found that the dextrin concentration increases both the optical band gap value and the transmission rate. (C) 2014 Elsevier B.V. All rights reserved.
