Yazar "Genisel, Mustafa Fatih" seçeneğine göre listele

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    Co-sputtered Cu2ZnTi(S:Se)4 absorbers for thin film solar cells
    (Pergamon-Elsevier Science Ltd, 2020) Batibay, Derya; Ocak, Yusuf Selim; Genisel, Mustafa Fatih; Turan, Rasit
    Thin film solar cells are an exciting topic for low cost and high efficient solar cells. Owing to the high price of the indium metal in the fabrication of copper indium gallium diselenide (CIGS) solar cells, Cu2ZnSn(SSe)(4) thin films are used as a new material to reduce the cost and increase the efficiency. As an alternative absorber material for solar cell production, Cu2ZnTi(S:Se)(4) thin films were deposited by the co-sputtering method at various temperatures. During the deposition, Cu, ZnSe and Ti targets were used as metal sources. The Cu2ZnTi(S:Se)(4) thin films were annealed in H2S:Ar (1:9) atmosphere. The morphological, structural and optical properties of Cu2ZnTi(S:Se)(4) thin films was analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) Raman spectroscopy and UV-Vis-NIR spectrometer. It was seen that the thin films had good optical absorption till the infrared region and the band gap of the Cu2ZnTi(S:Se)(4) thin films were smaller than the conventional Cu2ZnSnS4 thin films. Furthermore, fabrication of a solar cell with 1.96% power conversion efficiency was reported using a Cu2ZnTi(S:Se)(4) thin film as a low cost absorber layer. (c) 2019 Elsevier Ltd. All rights reserved.
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    CO2 sensing behavior of vertically aligned Si Nanowire/ZnO structures
    (Elsevier SCI LTD., 2021) Ocak, Yusuf Selim; Lamri Zeggar, Meryem; Genisel, Mustafa Fatih; Uzun, Nilufer Uslu; Aida, Mohammed Salah
    Metal oxide nanostructures are highly attractive for the fabrication of gas sensors due to their high surface-to-volume ratios. The design of novel structures has great importance to improve sensing behavior. Atomic layer deposited ZnO thin film on vertically aligned silicon nanowire (Si NW) arrays were used to understand the influence of etching time on CO2 sensing behavior of the SiNW/ZnO structure. The metal-assisted chemical etching method was used to realize SiNW arrays. The etching processes were performed for 5, 10, 30, and 60 min. The linear relationship between etching time and Si NW length was reported. 30 nm ZnO thin films were deposited on Si NWs by atomic layer deposition (ALD) method using diethyl Zinc and H2O as Zn and O-2 sources, respectively. The CO2 sensing properties of the SiNW/ZnO structures were examined at ambient temperature and low CO2 concentration. The testing measurement results reveal that the sensor realized on un-etched Si does not exhibit any sensitivity. While the SiNW/ZnO was sensitive to CO2, the sensor sensitivity increase with the etching time due to the increase in the specific reactive surface. Moreover, the realized sensors have a relatively low response and recovery times, in the range of 2-7 s, by comparison to the reported ones in the literature.
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    Electrical and optical properties of Cu2ZnSnS4 grown by a thermal co-evaporation method and its diode application
    (Elsevier Sci Ltd, 2014) Tombak, Ahmet; Ocak, Yusuf Selim; Genisel, Mustafa Fatih; Kilicoglu, Tahsin
    Cu2ZnSnS4 (CZTS) is low cost and constitutes non-toxic materials abundant in the earth crust. Environment friendly solar cell absorber layers were fabricated by a thermal co-evaporation technique. Elemental composition of the film was stated by energy dispersive spectroscopy (EDS). Some optical and electrical properties such as absorption of light, absorption coefficient, optical band gap charge carrier density, sheet resistance and mobility were extracted. Optical band gap was found to be as 144 eV, besides, charge carrier density, resistivity and mobility were found as 2.14 x 10(19) cm(-3), 8.41 x 10(-4) Omega cm and 3.45 x 10(2) cm(2) V-1 s(-1), respectively. In this study Ag/CZTS/n-Si Schottky diode was fabricated and basic diode parameters including barrier height, ideality factor, and series resistance were concluded using current-voltage and capacitance-voltage measurements. Barrier height and ideality factor values were found from the measurements as 0.81 eV and 4.76, respectively, for Ag/CZTS/n-Si contact. (C) 2014 Elsevier Ltd. All rights reserved.
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    Electrical parameters of a DC sputtered Mo/n-type 6H-SiC Schottky barrier diode
    (Elsevier Sci Ltd, 2014) Asubay, Sezai; Genisel, Mustafa Fatih; Ocak, Yusuf Selim
    A Mo/n-type 6H-SiC/Ni Schottky barrier diode (SBD) was fabricated by sputtering Mo metal on n-type 6H-SiC semiconductor. Before the formation of Mo/n-type 6H-SiC SBD, an ohmic contact was formed by thermal evaporation of Ni on n-type 6H-SiC and annealing at 950 degrees C for 10 min. It was seen that the structure had excellent rectification. The electrical parameters were extracted using its current-voltage (I-V) and capacitance-voltage (C-V) measurements carried out at room temperature. Very high (1.10 eV) barrier height and 1.635 ideality factor values were reported for Mo/n-type 6H-SiC using In plot. The barrier height and series resistance values of the diode were also calculated as 1413 eV and 69 Omega from Norde's functions, respectively. Furthermore, 1.938 eV barrier height value of Mo/n-type 6H-SiC SBD calculated from C-V measurements was larger than the one obtained from I-V data. (C) 2014 Elsevier Ltd. All rights reserved.
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    The influence of substrate temperature on RF sputtered CdS thin films and CdS/p-Si heterojunctions
    (Elsevier Sci Ltd, 2017) Bozkaplan, Cihat; Tombak, Ahmet; Genisel, Mustafa Fatih; Ocak, Yusuf Selim; Akkilic, Kemal
    Cadmium sulfide (CdS) thin films were deposited onto soda lime glasses and p-Si semiconductors at various substrate temperatures (40, 150 and 275 degrees C) by radio frequency (RF) sputtering technique. The effect of substrate temperature on morphological, structural and optical properties of CdS thin films were analyzed by means of atomic force microscopy (AFM), x-ray diffraction (XRD) and uv-vis spectrum data. The results showed that the average roughness (R-a) of thin films increased from 2.0 to 4.0 nm and all films had hexagonal wurtzite structure. The optical band gaps of CdS thin films varied between 2.46-2.43 eV. Characteristic parameters of CdS/p-Si heterojunctions including ideality factor, barrier height, series resistance and rectification ratio were measured. It was seen that both ideality factor and barrier height values of the heterojunctions increase with the increase substrate temperature. It was attributed to increase in inhomogenity of the thin films. Furthermore, the photoelectrical parameters of CdS/p-Si heterojunctions were studied.
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    Reactively Sputtered Cu2ZnTiS4 Thin Film as Low-Cost Earth-Abundant Absorber
    (Springer, 2017) Adiguzel, Seniha; Kaya, Derya; Genisel, Mustafa Fatih; Celik, Omer; Tombak, Ahmet; Ocak, Yusuf Selim; Turan, Rasit
    Cu2ZnTiS4 thin films have been deposited on glass by the reactive cosputtering technique with high-purity ZnS and Cu and Ti metals as targets and H2S as reactive gas. Cu2ZnTiS4 thin films were obtained at various temperatures and H2S flows and were annealed in H2S atmosphere. The structural, morphological, and optical properties of the Cu2ZnTiS4 thin films were examined by scanning electron microscopy, energy-dispersive spectroscopy, x-ray diffraction (XRD) analysis, and ultraviolet-visible (UV-Vis) spectroscopy. Agglomeration was found to increase with increasing temperature. The XRD peaks of the Cu2ZnTiS4 thin films were consistent with those of Cu2ZnSnS4. Furthermore, the optical bandgaps of the Cu2ZnTiS4 films were lower than those of conventional Cu2ZnSnS4 thin films.
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    Substrate temperature effects on reactively sputtered Cr2O3/n-Si heterojunctions
    (Iop Publishing Ltd, 2016) Ocak, Yusuf Selim; Issa, Ali Ahmed; Genisel, Mustafa Fatih; Tombak, Ahmet; Kilicoglu, Tahsin
    To see the effects of substrate temperature on Cr2O3/n-Si heterojunctions, Cr2O3 thin films were formed on n-Si and glass substrates at 40, 150 and 250 degrees C by radio frequency (RF) reactive sputtering technique. High purity Cr was used as target and oxygen was used as reactive gas. Optical properties of Cr2O3/n-Si thin films were analyzed using UV-vis data. The band gaps of the films were compared. The electrical properties of Cr2O3/n-Si heterojunction were tested by their current voltage (I-V) measurements in dark. It was observed that the heterojunction which was fabricated by forming Cr2O3 thin film at 250 degrees C gave better rectification. The characteristic electrical parameters such as barrier height, ideality factor and series resistance were calculated by using its I-V data. The influence of light intensity on photovoltaic effect behavior of the device was also calculated, finally the barrier height value of the structure obtained from capacitance-voltage (C-V) data were compared with the one calculated from I-V measurements.
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    Temperature dependent electrical characterization of RF sputtered MoS2/n-Si heterojunction
    (Elsevier Gmbh, 2017) Ocak, Yusuf Selim; Bozkaplan, Cihat; Ahmed, Honar Salah; Tombak, Ahmet; Genisel, Mustafa Fatih; Asubay, Sezai
    MoS2 is one of the most promising materials due to its exciting properties. Al/MoS2/n-Si heterojunction diode was acquired via the formation of a MoS2 thin film on n-Si semiconductor using radio frequency (RF) sputtering technique and an evaporation of Al metal on MoS2/n-Si structure. The morphological and optical properties of the RF sputtered MoS2 thin film were examined using atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV-vis data. The electrical parameters of Al/MoS2/n-Si heterojunction on temperature were investigated using its current-voltage (I-V) measurements within 150-400 K in the dark. The results showed that while the ideality factor and series resistance values of the junction decreased, the barrier height values increased with the increase in temperature. The linear correlation between ideality factor and barrier height values was also reported for Al/MoS2/n-Si heterojunction. (C) 2017 Elsevier GmbH. All rights reserved.