Yazar "Olğar, Mehmet Ali" seçeneğine göre listele

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    Fabrication of CZTS thin film on flexible Cu-foil substrate by two-stage process
    (2024) Olğar, Mehmet Ali; Zan, Recep
    In this research, CZTS thin films were grown on flexible Cu-foil substrates with varying sulfurization times. Distinct characterization methods were employed, including X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), optical transmission, and Photoluminescence (PL) measurements. Distinctive diffraction peaks characteristic of the kesterite CZTS phase were observed in the XRD analysis, occurring around at 2?= 28.45° (112), 47° (220/204), and 56° (312/116). Additionally, some secondary phases such as Cu2S and SnS were identified. Raman spectroscopy confirmed the presence of the kesterite CZTS phase, with a prominent peak detected at approximately ~336 cm-1, attributed to sulfur atom vibrations within the kesterite structure. Apart from CZTS structure, minor peaks suggesting the presence of the Cu2SnS3 (CTS) phase was detected. EDX analysis revealed compositions with Cu-poor content and Zn-rich content across all samples, with slight variations in sulfurization dwell times affecting the chemical composition. SEM imaging at different magnifications showed alterations in surface morphology and grain structures. Films sulfurized for 30 s and 60 s displayed a granular structure morphology, while extending the dwell time to 120 s resulted in a more compact surface morphology. Optical band gap values ranged between 1.57 and 1.60 eV. PL measurements consistently exhibited strong PL emission around 1.25 eV for all samples, attributed to various transitions within the band structure of CZTS film. The absence of observable band-to-band transitions in the PL measurements indicated the presence of intrinsic defect levels and recombination centers within CZTS. Overall, it was demonstrated in this study that CZTS thin films can be produced on flexible Cu-foils with short sulfurization times, thereby expanding the application areas of CZTS thin-film solar cells.
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    Fabrication of SnS thin film by rapid thermal processing: effect of annealing temperature in sulfurization process
    (2022) Çiriş, Ali; Olğar, Mehmet Ali
    In this study, the effect of sulfurization temperature on properties of SnS thin films was investigated. The SnS thin films were fabricated by two-stage method includes deposition of SnS films by magnetron sputtering using a single SnS target, followed by annealing/sulfurization treatment in Rapid Thermal Processing (RTP) system at 225, 300 and 375 °C temperatures. Several characterization techniques such as XRD, Raman spectroscopy, EDX, optical transmission and Van der Pauw were used for analyses of the films. The EDX analyses showed that all the samples had almost stoichiometric (S/Sn~1) chemical composition. However, the amount of sulfur in the samples increased slightly as the sulfurization temperature increased. XRD pattern of the films exhibited constitution of orthorhombic SnS structure regardless of annealing temperature. The SnS2 secondary phase was observed in addition to orthorhombic SnS phase in the sample annealed at highest reaction temperature (375°C). Raman spectroscopy measurements of the films verified constitution of orthorhombic SnS structure. The band gap of the films exhibited distinction from 1.42 to 1.81 eV regarding to annealing temperature. The electrical characterization of the most promising SnS thin film sulfurized at 300°C had resistivity and charge carrier concentration values 1.07x104 ?.cm and 1.70x1014 cm-3, respectively. Based on the all characterizations, it can be deduced that SnS thin film sulfurized at 300°C exhibited more outstanding structural and optical properties for potential solar cell applications.
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    Growth of Cu2ZnSnS4 Thin Films Using Moderate Annealing Temperature and Short Dwell Time
    (2019) Olğar, Mehmet Ali; Seyhan, Ayşe
    In this study CZTS thin films were fabricated by a two-stage process that sputter deposition of metallic Cu, Zn, and Sn on Mo coated glass substrates and annealing process at 500 °C using various short dwell times (4, 8, and 12 min) using Rapid Thermal Processing (RTP) approach. The X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and photoluminescence were employed to characterize the CZTS samples synthesized employing different sulfurization times. It was observed that all CZTS thin films showed Cu-poor and Zn-rich composition according to EDX results. XRD patterns displayed formation of kesterite CZTS and CuS secondary phases. Raman spectra of the films justified formation of kesterite CZTS phase for all CZTS thin films and formation of CTS phase, which is difficult to distinguish by XRD pattern of the films for CZTS-8 and CZTS-12 samples. SEM images of the films displayed dense, void-free, and inhomogeneous surface structure regardless of the sulfurization time. The optical band gap of the films as determined by photoluminescence was found to be about 1.36-1.37 eV.
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    INFLUENCE OF SULFURIZATION ON THE PROPERTIES OF Cu2ZnSnS4 (CZTS) THIN FILMS PREPARED BY A TWO-STAGE PROCESS
    (2019) Olğar, Mehmet Ali
    In this study, CZTS thin films were grown by a two-stage method involved sputter deposition of metallic Cu,Zn, and Sn layers to form Cu/Sn/Zn/Cu metallic stacks on glass and sulfurization of the metallic stacks at 540and 580 °C for 1 and 5 min in sulfur vapor atmosphere. The reacted samples at two different sulfurizationtemperatures and sulfurization times were characterized employing XRD, SEM, EDX, Raman spectroscopy,optical spectroscopy, and Van der Pauw methods. The metallic stacks and CZTS thin films showed Cu-rich andZn-poor composition. XRD patterns of the reacted films showed almost pure kesterite CZTS phase except forpresence of very small amount of Cu2-xS phase. Raman spectra of the films verified formation of kesterite phasein the films. SEM images showed that the CZTS540-1 sample had more compact, denser and uniform structure.Optical band gap values were found to be in good agreement with the literature. The CZTS540-1 thin filmshowed the highest carrier concentration and lowest resistivity values amongst the other samples.