Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 35Citation - Scopus: 35Cvd Graphene/Sic Uv Photodetector With Enhanced Spectral Responsivity and Response Speed(Elsevier, 2023) Jehad, Ala K.; Fidan, Mehmet; Ünverdi, Özhan; Çelebi, CemA self-powered, high-performance graphene/Silicon Carbide (G/4H-SiC) ultraviolet Schottky junction photodetector has been fabricated, and the effect of using monolayer and bilayer graphene on the device performance parameters was investigated. P-type graphene sheets were grown by the chemical vapor deposition (CVD) method, while 4H-SiC material consists of an epilayer structure of n-/n+ on bulk n-SiC. Two photodetector devices have been studied, one with monolayer graphene (MLG) and the other with bilayer graphene (BLG). The proposed photodetector structure reveals the highest spectral responsivity known of a G/4H-SiC UV photodetector so far. Electronic and optoelectronic characterizations were done under an ultraviolet wavelength range from 240 to 350 nm. The results show two spectral responsivity maxima (Rmax) at 285 nm and 300 nm wavelengths. Exhibiting two maxima in spectral responsivity and detectivity is caused by the constructive and destructive interference effects of multiple reflections at the SiC epilayer's interfaces. The photodetector devices exhibit high spectral responsivity (R ? 0.09 AW?1), maximum detectivity (D* ? 2.9 × 1012 Jones), and minimum noise equivalent power (NEP ? 0.17 pWHz-1/2) in both devices. Using bilayer graphene instead of monolayer showed no significant change in both the photogenerated current and the spectral responsivity due to the higher absorption coefficient of bilayer graphene, however, it exhibited a significant improvement in the response speed. The response speed was found to increase by 50 % when bilayer graphene was used as a hole collecting electrode in the G/4H-SiC junction. This is because bilayer graphene creates a narrower depletion layer and higher electric field, which promotes efficient charge separation and recombination. © 2023 Elsevier B.V.Article Citation - WoS: 9Citation - Scopus: 9Polymer-derived ceramic molten metal filters(Springer, 2022) Dizdar, Kerem Can; Kulkarni, Apoorv; Dışpınar, Derya; Soraru, Gian Domenico; Ahmetoğlu, Çekdar Vakıf; Semerci, TuğçeThis paper reports the synthesis and the performance of polymer-derived ceramic filters for molten metal filtration. Two different filter types were studied: foam filters produced from flexible polyurethane (PU) foams and additive manufacturing (AM) filters produced from thermoplastic polyurethane (TPU) cellular structure, and the results from all filter types were compared with that of the commercially used SiC foam filters. In both cases, the urethane-based polymeric template was impregnated with the preceramic solution, followed by pyrolysis. The produced ceramic components were then used to filter a molten Al alloy (A357), and the resulting Al samples were characterized for their mechanical properties. When filters were used, more reproducible and reliable mechanical properties were achieved compared to the samples obtained without any filtration. Among the different filters tested, the foam filters demonstrated better performance in comparison with the AM ceramic filters due probably to the three-dimensional interconnected porosity compared with the unidirectional cellular structure of the AM ceramic filters.