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: 2Citation - Scopus: 2Enhancing the Photo-Response Characteristics of Graphene/N-si Based Schottky Barrier Photodiodes by Increasing the Number of Graphene Layers(AVS, 2022) Fidan, Mehmet; Ünverdi, Özhan; Çelebi, CemThe impact of the number of graphene layers on the spectral responsivity and response speed of graphene/n-type Si (Gr/n-Si)-based Schottky barrier photodiodes is investigated. Gr/n-Si photodiode devices are fabricated by transferring chemical vapor deposition-grown graphene layers one by one on n-Si substrates, reaching up to three graphene layers. The devices show a clear rectifying Schottky character and have a maximum responsivity at a peak wavelength of 905 nm. Wavelength-resolved and time-dependent photocurrent measurements demonstrated that both spectral responsivity and response speed are enhanced as the number of graphene layers is increased from 1 to 3 on n-Si substrates. For example, the spectral responsivity and the response speed of the fabricated device were found to be improved by about 15% (e.g., from 0.65 to 0.75 AW-1) and 50% (e.g., 14 to 7 μs), respectively, when three graphene layers are used as the hole-collecting cathode electrode. The experimentally obtained results showed that the device parameters, such as spectral responsivity and response speed of Gr/n-Si Schottky barrier photodiodes, can be boosted simply by increasing the number of graphene layers on n-Si substrates.Article Citation - WoS: 1Citation - Scopus: 2Electron Field Emission From Sic Nanopillars Produced by Using Nanosphere Lithography(AVS Science and Technology Society, 2017) Yeşilpınar, Damla; Çelebi, CemField emitter arrays of silicon carbide based nanopillars with high emitter density were fabricated by using a combination of nanosphere lithography and inductively coupled plasma reactive ion etching techniques. The electron field emission characteristics of the produced nanopillars with two different aspect ratios and geometries were investigated, and the obtained results were compared with each other. The authors found that unlike the samples containing low aspect ratio SiC nanopillars with blunt tip apex, the samples comprising high aspect ratio nanopillars with sharp tip apex generate greater emission currents under lower electric fields. The nanopillars with sharp tip apex produced field emission currents up to 240 μA/cm2 under 17.4 V/μm applied electric field, while the nanopillars with blunt tip apex produced an emission current of 70 μA/cm2. The electric fields required to obtain 10 μA/cm2 current density are found to be 9.1 and 7.2 V/μm for the nanopillars with blunt and sharp tip apex, respectively. Time dependent stability measurements yielded stable electron emission without any abrupt change in the respective current levels of both samples.