Yazar "Okyay, Ali K." seçeneğine göre listele

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    Öğe
    An all-ZnO microbolometer for infrared imaging
    (Elsevier Science Bv, 2014) Kesim, Yunus Emre; Battal, Enes; Tanrikulu, M. Yusuf; Okyay, Ali K.
    Microbolometers are extensively used for uncooled infrared imaging applications. These imaging units generally employ vanadium oxide or amorphous silicon as the active layer and silicon nitride as the absorber layer. However, using different materials for active and absorber layers increases the fabrication and integration complexity of the pixel structure. In order to reduce fabrication steps and therefore increase the yield and reduce the cost of the imaging arrays, a single layer can be employed both as the absorber and the active material. In this paper, we propose an all-ZnO microbolometer, where atomic layer deposition grown zinc oxide is employed both as the absorber and the active material. Optical constants of ZnO are measured and fed into finite-difference-time-domain simulations where absorption performances of microbolometers with different gap size and ZnO film thicknesses are extracted. Using the results of these optical simulations, thermal simulations are conducted using finite-element-method in order to extract the noise equivalent temperature difference (NETD) and thermal time constant values of several bolometer structures with different gap sizes, arm and film thicknesses. It is shown that the maximum performance of 171 mK can be achieved with a body thickness of 1.1 mu m and arm thickness of 50 nm, while the fastest response with a time constant of 0.32 ms can be achieved with a ZnO thickness of 150 nm both in arms and body. (C) 2014 Elsevier B.V. All rights reserved.
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    Öğe
    Realization of Single Layer Microbolometer Detector Pixel Using ZnO Material
    (IEEE-Inst Electrical Electronics Engineers Inc, 2020) Tanrikulu, M. Yusuf; Yildizak, Cigdem; Okyay, Ali K.; Akar, Orhan; Sarac, Adem; Akin, Tayfun
    This paper presents the realization of a single layer microbolometer pixel fabricated using only ZnO material coated with atomic layer deposition. Due to the stress-free nature and high temperature coefficient of resistance of the ALD coated ZnO material, it can be used both as structural and active layers in microbolometer detectors. The design, simulations, and the fabrication optimization of two types of single layer ZnO microbolometer having pixel pitch of 35 mu m are shown in this study. The designed pixels have thermal conductances of 58 nW/K and 476 nW/K while their thermal time constant values are 1.62 ms and 0.24 ms. The temperature coefficient of resistance and 1/f corner frequency of fabricated resistors are measured to be -10 %/K and 302.5 Hz respectively. The absorption coefficients of both pixels are measured to be around 40 % in 8-12 mu m wavelength range. The fabricated pixels are the first examples of successfully obtained single layer ZnO microbolometer pixels in literature and the proposed structures can be used to decrease the design complexities and fabrication costs and increase the yield of the detectors making them possible to be used in low-cost applications.
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    Öğe
    Single layer microbolometer detector pixel using ZnO material
    (Spie-Int Soc Optical Engineering, 2018) Tanrikulu, M. Yusuf; Yildizak, Cigdem; Okyay, Ali K.; Akar, Orhan; Sarac, Adem; Akin, Tayfun
    This paper presents the development of a single layer microbolometer pixel fabricated using only ZnO material coated with atomic layer deposition. Due to the stress-free nature and high temperature coefficient of resistance of the ALD coated ZnO material, it can be used both as structural and active layers in microbolometer detectors. The design, simulations, and the fabrication optimization of 35. m single layer ZnO microbolometers are shown in this study. The designed pixel has a thermal conductance of 3.4x10(-7) W/K and a thermal time constant of 1.34 ms while it has a maximum displacement of 0.43 mu m under 1000g acceleration. This structure can be used to decrease the design complexities and fabrication costs and increase the yield of the detectors making them possible to be used in low-cost applications.