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: 5Citation - Scopus: 5Self-Powered Photodetector Array Based on Individual Graphene Electrode and Silicon-On Integration(Elsevier, 2023) Yanılmaz, Alper; Ünverdi, Özhan; Çelebi, CemOne of the key limitations for the device performance of the silicon (Si) based photodetector arrays is the optical crosstalk effect encountered between photoactive elements as well. The scope of this work is to reduce optical crosstalk and thus increasing the device performances with graphene and Si integration. This paper presents the design, fabrication process, and performance evaluation of self-powered individual Graphene/Silicon on Insulator (GSOI) based Schottky barrier photodiode array (PDA) devices. A 4-element GSOI Schottky barrier PDA with separate graphene electrodes is fabricated to examine possible optical crosstalk encountered between each diode in the array structure. Here, monolayer graphene is utilized as hole collecting separate electrode on individually arrayed n-type Si on SOI substrate by photolithography technique. Each diode in the array exhibited a clear rectifying Schottky character. Photoresponse characterizations revealed that all diodes had excellent device performance even in self-powered mode in terms of an Ilight/Idark ratio up to 104, a responsivity of ∼0.12 A/W, a specific detectivity of around 1.6 × 1012 Jones, and a response speed of ∼1.32 μs at 660 nm wavelength. As revealed by optical crosstalk measurement, the device with pixel pitch of 1.5 mm had a total crosstalk of about 0.10% (−60 dB) per array. These results showed that the optical crosstalk between neighboring n-Si elements can be greatly minimized when graphene is used as separated electrode on arrayed Si on SOI substrate. Our study is expected give an insight into the performance characteristics of GSOI PDA devices which have great potential to be used in many technological applications such as multi-wavelength light measurement, level metering, high-speed photometry and position/motion detection. © 2023 Elsevier B.V.Article Citation - WoS: 4Citation - Scopus: 4Graphene/Soi-based Self-Powered Schottky Barrier Photodiode Array(American Institute of Physics, 2022) Yanılmaz, Alper; Fidan, Mehmet; Ünverdi, Özhan; Çelebi, CemWe have fabricated a four-element graphene/silicon on insulator (SOI) based Schottky barrier photodiode array (PDA) and investigated its optoelectronic device performance. In our device design, monolayer graphene is utilized as a common electrode on a lithographically defined linear array of n-type Si channels on a SOI substrate. As revealed by wavelength resolved photocurrent spectroscopy measurements, each element in the PDA structure exhibited a maximum spectral responsivity of around 0.1 A/W under a self-powered operational mode. Time-dependent photocurrent spectroscopy measurements showed excellent photocurrent reversibility of the device with ∼1.36 and ∼1.27 μs rise time and fall time, respectively. Each element in the array displayed an average specific detectivity of around 1.3 × 1012 Jones and a substantially small noise equivalent power of ∼0.14 pW/Hz-1/2. The study presented here is expected to offer exciting opportunities in terms of high value-added graphene/Si based PDA device applications such as multi-wavelength light measurement, level metering, high-speed photometry, and position/motion detection.Article Citation - WoS: 22Citation - Scopus: 22Zinc Oxide and Metal Halide Perovskite Nanostructures Having Tunable Morphologies Grown by Nanosecond Laser Ablation for Light-Emitting Devices(American Chemical Society, 2020) Demirci Sankir, Nurdan; Abdullayeva, Nazrin; Altaf, Çiğdem Tuç; Kumtepe, Alihan; Yılmaz, Nazmi; Coşkun, Özlem; Sankir, Mehmet; Kurt, Hamza; Çelebi, Cem; Yanılmaz, AlperThis work reports a one-pot chemical bath deposition (CBD) method for the preparation of selectively grown, morphology-tunable zinc oxide (ZnO) nanostructures provided via straightforward nanosecond fiber laser ablation. Nanosecond fiber laser ablation is different from lithographic methods due to its simple, time saving, and efficient film scribing abilities. Here, multiple morphologies of the ZnO nanostructures on the same substrate have been grown via laser ablation of the ZnO seeding layer. Selective and controlled ablation of the titanium layer, ZnO growth inhibitor, resulted in systematic growth of nanorod arrays, while the application of extensive fluence energies resulted in the penetration of the laser beam until the glass substrate induced the nanoflake growth within the same CBD environment. The laser penetration depth has been numerically investigated via COMSOL Multiphysics heat module simulations, and the optical variations between two nanostructures (nanorod and nanoflake) have been examined via Lumerical FDTD. The simultaneous growth of two morphologies served as an efficient tool for the enhancement of photoluminescence intensities. It increased the average charge carrier lifetimes of the thin films from approximately 2.01 to 9.07 ns under the same excitation wavelengths. The amplification in PL performances has been accomplished via the capstone of all-inorganic halide perovskite (IHP) deposition that brought a successful conclusion to lifetime responses, which have been increased by 1.4-fold. The development of IHP sensitized nanoscaled multimorphological ZnO thin films can, therefore, be used as potential nanomaterials for light-emitting-device applications. © 2020 American Chemical Society.Article Citation - WoS: 54Citation - Scopus: 53Nitrogen Doping for Facile and Effective Modification of Graphene Surfaces(Royal Society of Chemistry, 2017) Yanılmaz, Alper; Tomak, Aysel; Akbalı, Barış; Bacaksız, Cihan; Özçeri, Elif; Arı, Ozan; Senger, Ramazan Tuğrul; Selamet, Yusuf; Zareie, Hadi M.We report experimental and theoretical investigations of nitrogen doped graphene. A low-pressure Chemical Vapor Deposition (CVD) system was used to grow large-area graphene on copper foil, using ethylene as the carbon source. Nitrogen-doped graphene (N-graphene) was prepared by exposing the graphene transferred to different substrates to atomic nitrogen plasma. The effect of varying nitrogen flow rates on doping of graphene was investigated while keeping the power and time constant during the process. The N-graphene was characterized via Raman Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Scanning Tunneling Microscopy and Spectroscopy (STM and STS), and Fourier Transform Infrared spectroscopy (FTIR). Raman mapping of N-graphene was also performed to show homogeneity of nitrogen on the graphitic lattice. XPS results have revealed the presence of different nitrogen configurations in the graphitic lattice with similar doping concentrations. Density functional theory (DFT) based calculations showed that the periodic adsorption of N atoms predominantly occurs on top of the C atoms rather than through substitution of C in our N-graphene samples. Our results indicate a feasible procedure for producing N-graphene with homogenous and effective doping which would be valuable in electronic and optical applications.