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: 9Citation - Scopus: 9High Voltage Response of Graphene/4h-sic Uv Photodetector With Low Level Detection(Elsevier, 2023) Çelebi, Cem; Ünverdi, Özhan; Çelebi, Cem; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyA self-powered graphene/silicon carbide (G/4H-SiC) ultraviolet photodetector of a p-i-n like-structure with high voltage response has been fabricated to detect and measure low intensity ultraviolet (UV) radiation. Bilayer graphene sheet grown by chemical vapor deposition (CVD) method was transferred on the top of an epilayer structure of n-/n+ 4 H-SiC. In this structure, two Schottky contacts were formed: one at G/ n- 4H-SiC interface and the other at bulk-4 H-SiC/Cr/Au interface. The photodetector's characteristic measurements revealed low dark current of - 0.58 nA and spectral voltage responsivity of - 0.75 V/W at 300 nm wavelength. Under low level UV illumination of 300 nm wavelength, the photodetector exhibited a leakage current and a photogenerated response voltage of 1.1 nA and 10 mV, respectively. The time-dependent photovoltage measurements displayed a rapid photovoltage response with rise and decay times of -74 ns and - 580 ns, respectively. This novel device holds promise for applications requiring sensitive and self-powered UV detection.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, Cem; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe 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: 6Citation - Scopus: 6Few-Layer Mos2 as Nitrogen Protective Barrier(IOP Publishing Ltd., 2017) Akbalı, Barış; Yanılmaz, Alper; Tomak, Aysel; Tongay, Sefaattin; Çelebi, Cem; Şahin, Hasan; Çelebi, Cem; 03.01. Department of Bioengineering; 04.05. Department of Pyhsics; 04.04. Department of Photonics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe report experimental and theoretical investigations of the observed barrier behavior of few-layer MoS2 against nitrogenation. Owing to its low-strength shearing, low friction coefficient, and high lubricity, MoS2 exhibits the demeanor of a natural N-resistant coating material. Raman spectroscopy is done to determine the coating capability of MoS2 on graphene. Surface morphology of our MoS2/graphene heterostructure is characterized by using optical microscopy, scanning electron microscopy, and atomic force microscopy. In addition, density functional theory-based calculations are performed to understand the energy barrier performance of MoS2 against nitrogenation. The penetration of nitrogen atoms through a defect-free MoS2 layer is prevented by a very high vertical diffusion barrier, indicating that MoS2 can serve as a protective layer for the nitrogenation of graphene. Our experimental and theoretical results show that MoS2 material can be used both as an efficient nanocoating material and as a nanoscale mask for selective nitrogenation of graphene layer.