Yazar "Tanrikulu, Mahmud Yusuf" seçeneğine göre listele

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    Atomic layer deposition synthesized TiOx thin films and their application as microbolometer active materials
    (A V S Amer Inst Physics, 2016) Tanrikulu, Mahmud Yusuf; Rasouli, Hamid Reza; Ghaffari, Mohammad; Topalli, Kagan; Okyay, Ali Kemal
    This paper demonstrates the possible usage of TiOx thin films synthesized by atomic layer deposition as a microbolometer active material. Thin film electrical resistance is investigated as a function of thermal annealing. It is found that the temperature coefficient of resistance values can be controlled by coating/annealing processes, and the value as high as -9%/K near room temperature is obtained. The noise properties of TiOx films are characterized. It is shown that TiOx films grown by atomic layer deposition technique could have a significant potential to be used as a new active material for microbolometer-based applications. (C) 2016 American Vacuum Society.
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    Digitally alloyed ZnO and TiO2 thin film thermistors by atomic layer deposition for uncooled microbolometer applications
    (A V S Amer Inst Physics, 2017) Tilkioglu, Bilge T.; Bolat, Sami; Tanrikulu, Mahmud Yusuf; Okyay, Ali Kemal
    The authors demonstrate the digital alloying of ZnO and TiO2 via atomic layer deposition method to be utilized as the active material of uncooled microbolometers. Depositions are carried out at 200 degrees C. Crystallinity of the material is shown to be degraded with the increase of the Ti content in the grown film. A maximum temperature coefficient of resistance (TCR) of 5.96%/K is obtained with the films containing 12.2 at. % Ti, and the obtained TCR value is shown to be temperature insensitive in the 15-22 degrees C, thereby allowing a wide range of operation temperatures for the low cost microbolometers. (C) 2017 American Vacuum Society.
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    Enhancing near-infrared sensitivity of CMOS image sensors using a hemispherical photon-trapping structure
    (Springer, 2025) Yucekul, Mustafa Ozber; Tanrikulu, Mahmud Yusuf
    CMOS image sensors are extensively utilized in applications ranging from consumer electronics to biomedical imaging and autonomous systems. Despite their high efficiency in the visible spectrum, their sensitivity in the near-infrared (NIR) region remains significantly low due to the limited absorption of silicon beyond 700 nm. To address this challenge, we propose a novel light-trapping strategy incorporating a hemispherical structure at the silicon interface. This design facilitates the direct transmission of normally incident light into the silicon layer while enhancing light scattering and redistribution. Additionally, a pyramidal structure positioned below the silicon layer refracts transmitted light, further improving absorption. To minimize optical crosstalk between adjacent pixels, a deep trench isolation (DTI) structure is implemented. The optical performance of the proposed structure is evaluated through finite-difference time-domain (FDTD) simulations, demonstrating up to a 36% enhancement in optical efficiency at a wavelength of 1100 nm compared to conventional BSI CMOS image sensor designs. These findings highlight the potential of hemispherical photon-trapping strategies for enhancing CMOS image sensor performance in NIR applications such as machine vision and biomedical imaging.
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    Enhancing near-infrared sensitivity with GaAs-based hybrid CMOS image sensors
    (SPIE-Society of Photo-Optical Instrumentation Engineers, 2025) Yucekul, Mustafa Ozber; Tanrikulu, Mahmud Yusuf
    Complementary metal-oxide-semiconductor (CMOS) image sensors are widely used in applications such as time-of-flight systems, machine vision, mobile devices, and medical imaging due to their versatility and compact structure. However, enhancing their sensitivity in the near-infrared (NIR) region remains a significant challenge, largely due to insufficient light absorption within this spectral range. We propose an innovative solution to this limitation by integrating GaAs semiconductor material with silicon in a hybrid CMOS image sensor. The design incorporates a 2 mu mx2 mu m pixel architecture combined with a deep trench isolation structure, which significantly enhances light absorption and efficiency in the NIR region. This approach achieves more than a twofold increase in NIR sensitivity in the 800- to 1000-nm wavelength range compared with conventional backside-illuminated CMOS image sensors. Simulation results highlight the substantial potential of the GaAs-based hybrid structure in advancing the performance of CMOS image sensors for applications requiring improved sensitivity in the NIR region. To the best of our knowledge, the proposed structure is the first of its kind reported in the literature.
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    LWIR all-atomic layer deposition ZnO bilayer microbolometer for thermal imaging
    (Spie-Soc Photo-Optical Instrumentation Engineers, 2017) Poyraz, Muhammet; Gorgulu, Kazim; Sisman, Zulkarneyn; Tanrikulu, Mahmud Yusuf; Okyay, Ali Kemal
    We propose an all-ZnO bilayer microbolometer, operating in the long-wave infrared regime that can be implemented by consecutive atomic layer deposition growth steps. Bilayer design of the bolometer provides very high absorption coefficients compared to the same thickness of a single ZnO layer. High absorptivity of the bilayer structure enables higher performance (lower noise equivalent temperature difference and time constant values) compared to single-layer structure. We observe these results computationally by conducting both optical and thermal simulations. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    Priority and age specific vaccination algorithm for the pandemic diseases: a comprehensive parametric prediction model
    (Bmc, 2022) Tutsoy, Önder; Tanrikulu, Mahmud Yusuf
    Background There have been several destructive pandemic diseases in the human history. Since these pandemic diseases spread through human-to-human infection, a number of non-pharmacological policies has been enforced until an effective vaccine has been developed. In addition, even though a vaccine has been developed, due to the challenges in the production and distribution of the vaccine, the authorities have to optimize the vaccination policies based on the priorities. Considering all these facts, a comprehensive but simple parametric model enriched with the pharmacological and non-pharmacological policies has been proposed in this study to analyse and predict the future pandemic casualties. Method This paper develops a priority and age specific vaccination policy and modifies the non-pharmacological policies including the curfews, lockdowns, and restrictions. These policies are incorporated with the susceptible, suspicious, infected, hospitalized, intensive care, intubated, recovered, and death sub-models. The resulting model is parameterizable by the available data where a recursive least squares algorithm with the inequality constraints optimizes the unknown parameters. The inequality constraints ensure that the structural requirements are satisfied and the parameter weights are distributed proportionally. Results The results exhibit a distinctive third peak in the casualties occurring in 40 days and confirm that the intensive care, intubated, and death casualties converge to zero faster than the susceptible, suspicious, and infected casualties with the priority and age specific vaccination policy. The model also estimates that removing the curfews on the weekends and holidays cause more casualties than lifting the restrictions on the people with the chronic diseases and age over 65. Conclusion Sophisticated parametric models equipped with the pharmacological and non-pharmacological policies can predict the future pandemic casualties for various cases.
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    The evolution of nanoscale pores with post-annealing and the structure-electrical property correlation in vanadium oxide thin films
    (Elsevier Science Sa, 2022) Dirican, Emrah; Yagci, Ahmet Murat; Tanrikulu, Mahmud Yusuf; Okszoglu, Ramis Mustafa
    Structure-property correlation in vanadium oxide nanoscale thin films used in uncooled thermal detectors is a crucial question for device performance. The purpose of this work is to investigate the evolution of the nanoscale pores with post-annealing temperature and its correlation to electrical properties. It is observed that the as-deposited film has an amorphous matrix containing nanoscale crystal grains of VO2, V2O5, and V6O13 phases, and additionally nanoscale fibrous-like pores. The film post-annealed at 200 C under high purity N-2 atmosphere for 3 h possesses nanoscale crystal grains predominantly with the VO2 phase besides V6O13 and nanoscale spherical pores. After post-annealing at 300 ?, a clear enhancement in crystallinity and diminishing of amorphous structure has been found, and the film contains VO2, V2O3, and V(6)O(13 )phases, additionally larger pores and cracks. The electrical resistance and temperature coefficient of resistance increase with increasing temperature, whereas the electrical noise reduces after annealing at 200 ?& nbsp;and increases again at 300 ?. The best combination of values for 1/f noise corner frequency (5.7 kHz), electrical resistance (90 k omega), and temperature coefficient of resistance (-2.71 %K- 1) is obtained for the film after post-annealing at 200 ?, favorable for application.