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Öğe Computer assisted optimization of copper sulphide thin film coating parameters on glass substrates(Elsevier, 2015) Yucel, Ersin; Yucel, Yasin; Gokhan, DidemIn this work, copper sulphide (CuS) thin films were deposited on glass substrates by chemical bath deposition method under different pH, deposition temperature, stirring speed and deposition time. The effects of process parameters, such as pH from 1.8 to 2.2, deposition temperature from 30 to 50 degrees C, stirring speed from 50 to 250 rpm and deposition time from 8 to 40 h on the band gap, were optimized by central composite design (CCD) of response surface methodology (RSM). Five-level-four-factor CCD was employed to evaluate the effects of the deposition parameters on the band gap of CuS thin films. A quadratic model was established as a functional relationship between four independent variables and the band gap. Analysis of variance revealed that the proposed model was adequate. The optimum pH, deposition temperature, stirring speed and deposition time were found to be 2.10, 44.33 degrees C, 200 rpm, and 32h, respectively. Under these conditions, the experimental band gap of CuS was observed as 2.74 eV, which was well in close agreement with predicted value (2.71 eV) by the model. (C) 2015 Elsevier B.V. All rights reserved.Öğe Deposition of PbS thin films using a continuous flow reactor: Comparison of the modified technique with conventional methods in the coating of PbS thin film on the substrate(Elsevier, 2022) Yucel, Ersin; Yucel, YasinA reactor was designed to coat the PbS thin film on glass substrate by continuous flow. A methodology is proposed to deposit PbS films based on reducing the roughness via a laminar and continuous flow in the reactor without being affected by the chaotic properties of the turbulent flow. The modified coating method was named flow-through chemical deposition (FTCD). The morphological analysis demonstrated that the surface roughness of PbS films deposited by the FTCD method was lower than the other films. The wetting behaviour of PbS surfaces is consistent with the roughness of the PbS layers coated on the substrate. The results revealed that the properties of the films were influenced from the deposition method, the substrate position and the movement of the chemical solution in the reaction medium. The developed innovative approach has shown promising results for the chemical synthesis of PbS films in the context of surface modification.Öğe Effect of coumarin addition on the superconducting properties of bulk MgB2 superconductors(Iop Publishing Ltd, 2019) Kizilkoca, Bunyamin; Yucel, ErsinIn the present study, undoped and coumarin doped bulk MgB2 superconductors were successfully fabricated by using the wet-mixing method and conventional solid-state reaction method. It was found that grain size of the MgB2 samples decreases from 24.3 to 20.5 nm with increasing coumarin content. Actual carbon substitution level in the MgB2 lattice is calculated to be from 0.70% to 1.75% for different coumarin contents. The critical current density and flux pinning force of MgB2 were enhanced by coumarin doping. Among the all MgB2 samples, the highest critical current density value was achieved to be 1 x 10(5) A cm(-2) in the self field at 5 K. It was obtained that coumarin additive did not reduce superconducting transition temperatures of the MgB2 samples. The results show that coumarin assisted production of MgB2 is a promising way to improve its superconducting properties.Öğe Effect of doping concentration on the structural, morphological and optical properties of Ca-doped PbS thin films grown by CBD(Elsevier Gmbh, Urban & Fischer Verlag, 2017) Yucel, Ersin; Yucel, YasinPure and calcium doped lead sulfide (PbS) thin films were prepared by chemical bath deposition (CBD) method. The effects of calcium doping content on their structural, morphological and optical properties were investigated by X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and UV-vis spectroscopy measurements, respectively. According to X-Ray diffraction patterns all films were polycrystalline in nature, with a cubic crystal structure. It was observed from SEM analysis that calcium doping level affected the film morphology and surface roughness. Incorporation of Ca was confirmed from Energy dispersive X-Ray analysis results. Tauc method was used to estimate the optical band gap energies (E-g) of the pure and calcium doped films. UV-vis analysis showed that the transmittance of the samples varied between 15.3 and 20%. Also, it was observed that transmittance of deposited films increased with adding of calcium. Further, the optical energy band gap values were found to enhance (1.92-2.50 eV) with increasing the Ca content in PbS films. (C) 2017 Elsevier GmbH. All rights reserved.Öğe Effect of pH on the structural, optical and nanomechanical properties of CdS thin films grown by chemical bath deposition(Elsevier Sci Ltd, 2016) Yucel, Ersin; Sahin, OsmanCdS nano-structured thin films were prepared on glass substrates with chemical bath deposition technique for different pH values. The effects of pH and annealing on the structural, optical and nanomechanical properties of CdS films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis spectrophotometer and nanoindentation techniques. The results of XRD analysis and SEM investigation reveal that both different pH values of the bath solution and annealing affect the crystal structure and the surface morphology of the films markedly. Also, the results of the optical absorption show that the E-g values of the films decrease with increasing pH values. In this kind of study the mechanical properties of the CdS thin films determined using nanoindentation tests are being reported here for the first time. Nanoindentation experimental results show that nanohardness and elastic modulus values exhibit a peak load dependence. Our results reveal that, the annealing of CdS films at 300 degrees C results in slow and normal grain coarsening. The slow grain growth also influences the lattice strain (microstrain) which effects nanohardness and elastic modulus. The results also indicate that there is a direct dependence of the physical and optical properties of the CdS films on pH and annealing process. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe The effects of coumarin additive on the properties of CdS thin films grown by chemical bath deposition(Elsevier Sci Ltd, 2015) Yucel, Ersin; Kahraman, SuleymanCdS thin films have been obtained on glass substrates by using chemical bath deposition technique. Different concentrations of coumarin were used as an additive in the growth solutions, for the first time. The effects of coumarin on the properties of the as-deposited and annealed CdS thin films were investigated. It was found that increasing coumarin concentration in the growth solution remarkably affects the crystallinity and uniformity of the films. The 1% and 2% presence of coumarin enhanced the surface morphology while higher concentrations decreased surface uniformity. In the optical band gap values of both as-deposited and annealed films, a decrease has been observed with increasing additive concentration. Through temperature dependent resistance measurements of the films, impurity levels' electrical activation energies for each film have been estimated by means of the obtained discrete linear regions indicating different conduction mechanisms. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Öğe Fabrication and characterization of Sr-doped PbS thin films grown by CBD(Elsevier Sci Ltd, 2017) Yucel, Ersin; Yucel, YasinIn this work, undoped and Strontium-doped lead sulfide (PbS) thin films were deposited on glass substrates by chemical bath deposition (CBD) technique. The effect of Sr doping concentration on the structural, morphological and optical properties of the PbS thin films was studied. Changing in crystallite size, microstrain, dislocation density and band gap energy values of the PbS thin films as a function of Sr concentration were investigated by scanning electron microscopy (SEM), X-Ray diffraction (XRD) and UV-visible spectroscopy measurements. Energy dispersive X-Ray analysis (EDS) results indicated that nanostructured PbS films is doped with Sr without causing much lattice strain. According to XRD experiments crystallite size of the films is decreasing from 17.90 to 9.14 nm with increasing Sr-doping. UV-visible analysis showed that the band gap value of PbS thin films increased from 1.73 ev to 2.19 eV by changing Sr doping concentration from 0% to 5%.Öğe Growth and characterization of Fe-doped CuO/ZnO binary oxide thin films for possible optoelectronic applications(Elsevier, 2024) Sogan, Serra; Yucel, Ersin; Sarikaya, Ebru Karakas; Kahveci, Osman; Aydin, Rasit; Akkaya, Abdullah; Sahin, BuenyaminNanoscale binary oxide thin film structures of pristine and Fe-substituted CuO/ZnO have been produced on sodalime glass substrates by the SILAR method and characterized by different acceptable analytical approaches. The more irregular and lumpy ZnO in the pristine CuO/ZnO binary thin film sample evolved into more regular and hexagonal prismatic structures with the addition of Fe. XRD patterns of the samples indicated that both monoclinic CuO and hexagonal ZnO phases were present without any impurities. Optical analyses by meaning absorbance and transmittance measurements exhibit an important change in the energy band gap and transmittance value with the Fe doping ratio. The energy band edges of the bare sample shift to red with increasing Fe percentage in the starting solution, presumably due to an increase in the carrier concentration. The transfer length method (TLM) is used to define the conductivity properties of the samples, which considers the contact properties and structural features of thin films. The minimum specific contact resistivity of 0.865 x 10 6 Omega square was obtained by 3.0 % Fe-implemented CuO/ZnO binary oxide samples, and the addition of Fe increased the effective transfer length of thin films.Öğe Mathematical modelling based on deposition parameters for optical band gap estimation of Sb2S3 thin films(Elsevier, 2024) Yucel, Ersin; Yucel, YasinA mathematical prediction model was developed to predict the band gap of Sb2S3 films based on the synthesis parameters. For the optimization of process parameters, a chemometric optimization approach was used instead of the traditional method. The band gaps of chalcogenide films were measured between 1.68 eV and 1.98 eV. The developed model was able to predict the band gap of the optimized Sb2S3 sample, measured as 1.71 eV, as 1.77 eV. The mathematical model achieved the band gap prediction of both the optimized Sb2S3 film and the test sample with a relative error of 3.51% and 2.23%, respectively. The data revealed that the developed model could reliably predict the band gap of Sb2S3 nanoparticles with a relative error of less than 5%. These findings may provide a significant advantage in nanoscale applications in terms of better understanding the predictability of the band gap of Sb2S3 films prior to synthesis.Öğe Optimization and modelling of preparation conditions of CuS thin films deposited by successive ionic layer adsorption and reaction (SILAR) method using response surface methodology(Springer, 2015) Yucel, Yasin; Yucel, Ersin; Gokhan, DidemIn this study, CuS thin films were deposited on glass substrates by SILAR method with different pH, dipping time and dipping cycles. For the first time, response surface methodology was used for optimization CuS thin film coating parameters. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition parameters (pH, dipping time and dipping cycles) on the optical band gap of the films. The significant level of the main effects and the interactions were investigated by analysis of variance. The morphological, structural and optical properties of the films were investigated by SEM, XRD and UV-Vis. The optimum pH, dipping time and dipping cycles were found to be 11.5, 31 s and 15 cycles, respectively. Under these conditions, the experimental band gap of CuS was observed as 2.18 eV which was well in close agreement with predicted value (2.11 eV) by the model. Quality of the film was improved after chemometrics optimization.Öğe Optimization of deposition conditions of CdS thin films using response surface methodology(Elsevier Science Sa, 2014) Yucel, Ersin; Guler, Nuray; Yucel, YasinCadmium sulfide (CdS) thin films were prepared on glass substrates by chemical bath deposition (CBD) technique under different pH, stirring speed and deposition time. Response Surface Methodology (RSM) and Central Composite Design (CCD) were used to optimization of deposition parameters of the CdS thin films. RSM and CCD were also used to understand the significance and interaction of the factors affecting the film quality. Variables were determined as pH, stirring speed and deposition time. The band gap was chosen as response in the study. Influences of the variables on the band gap and the film quality were investigated. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition conditions parameters such as pH (10.2-11.8), stirring speed (132-468 rpm) and deposition time (33-67 min) on the band gap of the films. The samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and ultraviolet-visible spectroscopy (UV-vis) measurements. The optimal conditions for the deposition parameters of the CdS thin films have been found to be: pH 11, 361 of stirring speed and 55 min of deposition time. Under the optimal conditions theoretical (predicted) band gap of CdS (2.66 eV) was calculated using optimal coded values from the model and the theoretical value is good agreement with the value (2.72 eV) obtained by verification experiment. (C) 2013 Elsevier B. V. All rights reserved.Öğe Optimization of fabrication conditions of MgB2/Fe superconducting tapes using response surface methodology(Springer, 2012) Yucel, Ersin; Yucel, Yasin; Belenli, IbrahimWe have optimized fabrication conditions of MgB2/Fe superconducting monofilament tapes fabricated using ex-situ powder-in-tube method without any intermediate annealing. Influences of three effective parameters (annealing temperature, annealing time and argon (Ar) gas atmosphere pressure during the heat treatments) on the transport critical current densities (J(c)) were investigated. The samples were characterized using X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectrometer, optical microscope, critical transition temperature and J(c) measurements. Response surface methodology was used to optimize the conditions for the maximum J(c) of the samples and to understand the significance and interaction of the factors affecting J(c). 3-level-3-factor central composite design was employed to evaluate the effects of the fabrication conditions parameters such as annealing temperatures (850-950 A degrees C), annealing times (30-120 min.) and Ar pressures (1-5 bars) on J(c) of the samples. Based on the analysis of ridge max, the optimum fabrication conditions were as follows: annealing temperature 948 A degrees C, annealing time 58 min. and Ar pressure 3 bars.Öğe Optimization of growth parameters for absorber material SnS thin films grown by SILAR method using response surface methodology(Springer, 2017) Yucel, Ersin; Yucel, Yasin; Durak, MustafaIn this paper, SnS films were deposited on glass substrates by successive ionic layer adsorption and reaction method under different deposition conditions. Quality of semiconductor thin films depends on their deposition parameters. The deposition process was optimized by the application of five-level-three-factor central composite design. Response surface methodology was used to optimize deposition parameters including temperature of precursor solutions (27-43 degrees C), dipping time (3-37 s) and dipping cycles (23-57 cycles) for deposition of the SnS thin films. The effect of the deposition parameters on the film growth has been studied using the experimental design methodology. The optimum fabrication conditions were found to be 40 degrees C (temperature), 23.4 s (dipping time) and 50 cycles (dipping cycles), respectively. Under optimum terms, the E-g value of SnS nanostructures calculated as 1.73 eV. The optimized value showed a good fit to the predicted value (1.67 eV). In addition, the structural, optical and morphological properties of thin films were investigated.Öğe Optimization of synthesis conditions of PbS thin films grown by chemical bath deposition using response surface methodology(Elsevier Science Sa, 2015) Yucel, Ersin; Yucel, Yasin; Beleli, BuseIn this study, PbS thin films were synthesized by chemical bath deposition (CBD) under different deposition parameters. Response surface methodology (RSM) was used to optimize synthesis parameters including amount of tri-sodium citrate (0.2-0.8 mL), deposition time (14-34 h) and deposition temperature (26.6-43.4 degrees C) for deposition of the films. 5-level-3-factor central composite design (CCD) was employed to evaluate effects of the deposition parameters on the response (optical band gap of the films). The significant level of both the main effects and the interaction are investigated by analysis of variance (ANOVA). The film structures were characterized by X-ray diffractometer (XRD). Morphological properties of the films were studied with a scanning electron microscopy (SEM). The optical properties of the films were investigated using a UV-visible spectrophotometer. The optimum amount of tri-sodium citrate, deposition time and deposition temperature were found to be 0.7 mL, 18.07 h and 30 degrees C respectively. Under these conditions, the experimental band gap of PbS was 2.20 eV, which is quite good correlation with value (1.98 eV) predicted by the model. (C) 2015 Elsevier B.V. All rights reserved.Öğe Optimization of zinc sulfide thin film coating process using response surface methodology(Springer, 2015) Yucel, Ersin; Yucel, YasinZinc sulfide (ZnS) thin films have been deposited on glass substrates at room temperature using chemical bath deposition method. Application of response surface methodology and central composite design for optimizing the ZnS films deposition parameters and understanding the significance and interaction of the factors affecting the film quality was discussed in this work. pH, stirring speed and deposition time were investigated as variables and band gap was selected as response in this study. The samples were characterized using X-Ray diffraction, scanning electron microscope and ultraviolet-visible spectroscopy measurements. The optimal conditions for the deposition parameters of the ZnS thin films have been found to be: pH of 10.1, stirring speed of 163 rpm and deposition time of 31 h. Under these conditions, the experimental band gap of ZnS was 3.95 eV, which is well in close agreement with value (3.97 eV) predicted by the model.Öğe Process optimization for window material CdS thin films grown by a successive ionic layer adsorption and reaction method using response surface methodology(Elsevier Science Sa, 2016) Yucel, Ersin; Yucel, Yasin; Durak, MustafaSuccessive ionic layer adsorption and reaction (SILAR) method were used to synthesize of cadmium sulfide (CdS) thin films on support material under different synthesis conditions. Response surface methodology (RSM) based on central composite design (CCD) was used to design the experiment and to optimize selected operating parameters: temperature (degrees C), dipping time (s) and dipping cycles (cycles). Using RSM, second order polynomial equation was obtained for optical band gap of the films by multiple regression analysis. Analysis of variance revealed that the proposed model was adequate. According to the results of RSM, optimum synthesis conditions of CdS thin films were determined to be temperature of 30.1 degrees C, dipping time of 29.5 s and dipping cycles of 30 cycles. Band gap of CdS (2.43 eV) in the optimized synthesis condition was in good agreement with the value predicted by the second order polynomial equation (2.36 eV), thereby confirming its validity. The samples were characterized using X-Ray diffraction, scanning electron microscope and ultraviolet-visible spectroscopy measurements. (C) 2016 Elsevier B.V. All rights reserved.Öğe Process optimization of deposition conditions of PbS thin films grown by a successive ionic layer adsorption and reaction (SILAR) method using response surface methodology(Elsevier, 2015) Yucel, Ersin; Yucel, Yasin; Beleli, BuseIn this study, lead sulfide (PbS) thin films were synthesized by a successive ionic layer adsorption and reaction (SILAR) method with different pH, dipping time and dipping cycles. Response surface methodology (RSM) and central composite design (CCD) were successfully used to optimize the PbS films deposition parameters and understand the significance and interaction of the factors affecting the film quality. 5-level-3-factor central composite design was employed to evaluate the effects of the deposition parameters (pH, dipping time and dipping cycles) on the response (the optical band gap of the films). Data obtained from RSM were subjected to the analysis of variance (ANOVA) and analyzed using a second order polynomial equation. The optimal conditions for the PbS films deposition have been found to be pH of 9.1, dipping time of 10 s and dipping cycles of 10 cycles. The predicted band gap of PbS film was 2.13 eV under the optimal conditions. Verification experiment (2.24 eV) confirmed the validity of the predicted model. The film structures were characterized by X-ray diffractometer (XRD). Morphological properties of the films were studied with a scanning electron microscopy (SEM). The optical properties of the films were investigated using a UV-visible spectrophotometer. (C) 2015 Elsevier B.V. All rights reserved.Öğe Superconducting properties of saccharin-added bulk MgB2 superconductors(Springer, 2020) Yucel, ErsinIn this paper, saccharin was used as the carbon source for addition in bulk MgB2 superconductor. MgB2 samples were successfully prepared with saccharin and ethanol-processed boron using a wet-mixing method. Actual carbon substitution level in the MgB2 lattice increased from 0 to 3.58% with the increasing saccharin content up to 1% and slightly decreased at higher saccharin content. While the 0.1% saccharin-added sample showed the highest critical current density of 2.17 x 10(5) A/cm(2) in the self field at 20 K, the undoped sample showed a lower critical current density of 1.19 x 10(5) A/cm(2). In addition to this, the critical current densities in 4 T field at 10 K for 0.1% and 0.5% saccharin-added samples were calculated to be 1.5 x 10(4) and 1 x 10(4) A/cm(2), respectively. It was obtained that the addition of low-rate saccharin content did not affect the superconducting transition temperature of the MgB2 sample. These results show that MgB2 fabrication with small amount of saccharin is beneficial to improve critical current density.Öğe Surface roughness prediction in SILAR coating process of ZnO thin films: Mathematical modelling and validation(Elsevier, 2023) Yucel, Yasin; Otuzbir, Omer; Yucel, ErsinThis study aimed to evaluate the effect of SILAR coating parameters on the surface roughness of ZnO thin films with a chemometric approach and to develop a mathematical model that can be used to predict the surface roughness of the films depending on the coating parameters. The selected process parameters for the SILAR coating of ZnO are the ammonia solution amount, cycle number and stirring speed. The effect of coating pa-rameters on ZnO thin film roughness was investigated with the help of RSM. A statistical estimation model was developed and used to estimate the effect of parameters on roughness. The adequacy of the developed mathe-matical model was tested with ANOVA. When the data obtained were examined, it was understood that the amount of NH4OH played a decisive role in the morphology of ZnO coatings. The surface roughness of the optimized coating was measured as 213.4 nm for Rq and 177.8 nm for Ra, and the developed mathematical models estimated the surface roughness of the coating as 214.9 nm for Rq and 179.6 nm for Ra. The findings revealed that the mathematical models developed to predict the surface roughness of ZnO films are accurate and reliable in predicting the Rq and Ra values.Öğe Synthesis and characterization of lead sulfide thin films by coumarin assisted CBD method(Elsevier Gmbh, 2018) Yucel, Yasin; Yucel, ErsinCoumarin which is a natural substance found in many plants is an organic chemical compound. In this study, we investigated the effects of coumarin adding during the growth of lead sulfide (PbS) thin films by chemical bath deposition (CBD). It was found that significant improvements were observed in the optical and structural properties of the films coated in the presence of coumarin. X-Ray diffraction, UV-vis spectrophotometry and scanning electron microscopy were used to systematically investigate the effect of coumarin on the characteristic properties of the PbS films. X-ray diffraction measurements have revealed that the increasing of coumarin content caused the decreasing the crystallite size of the films. On the other hand, UV-vis analysis showed that the band gap value of the coated samples increased from 1.80 eV to 2.53 eV by changing additive content from 0 to 4%. Also, UV-vis spectra exhibited that the transmittance of the samples varied between 37 and 50%. Further, surface roughness measurements showed that film morphology was influenced by the coumarin content. The results show that coumarin assisted growth of PbS nanostructures is a promising way to improve its physical properties. (C) 2018 Elsevier GmbH. 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