Yazar "Tanrikulu, M. Yusuf" seçeneğine göre listele

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    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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    Atomic-layer-deposited zinc oxide as tunable uncooled infrared microbolometer material
    (Wiley-V C H Verlag Gmbh, 2014) Battal, Enes; Bolat, Sami; Tanrikulu, M. Yusuf; Okyay, Ali Kemal; Akin, Tayfun
    ZnO is an attractive material for both electrical and optical applications due to its wide bandgap of 3.37eV and tunable electrical properties. Here, we investigate the application potential of atomic-layer-deposited ZnO in uncooled microbolometers. The temperature coefficient of resistance is observed to be as high as -10.4%K-1 near room temperature with the ZnO thin film grown at 120 degrees C. Spectral noise characteristics of thin films grown at various temperatures are also investigated and show that the 120 degrees C grown ZnO has a corner frequency of 2kHz. With its high TCR value and low electrical noise, atomic-layer-deposited (ALD) ZnO at 120 degrees C is shown to possess a great potential to be used as the active layer of uncooled microbolometers. The optical properties of the ALD-grown ZnO films in the infrared region are demonstrated to be tunable with growth temperature from near transparent to a strong absorber. We also show that ALD-grown ZnO can outperform commercially standard absorber materials and appears promising as a new structural material for microbolometer-based applications.
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    Hexagonal microbolometer pixel for flexible substrates
    (Institute of Electrical and Electronics Engineers Inc., 2017) Yildizak, Çi?dem; Tanrikulu, M. Yusuf
    Nature becomes a source of inspiration to many researches on imaging systems. Imaging features owned by biological forms such as high resolution, wide field of view, high depth of field, high sensitivity to motion and light are attractive reasons to mimic the nature in imaging system applications. In this study, an arthropod eye's hexagonal shaped ommatidia are taken as a model for uncooled microbolometer pixel structure. A hexagonal pixel with 34 ?m diagonal length which has the thermal conductance value of 1.48×107 W/K and the time constant value of 0.69 ms is designed for the first time in literature. The pixels are estimated to have an NETD of less than 250 mK in a potential 384×288 microbolometer array. © 2017 EMO (Turkish Chamber of Electrical Enginners).
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    Hexagonal Microbolometer Pixel for Flexible Substrates
    (IEEE, 2017) Yildizak, Cigdem; Tanrikulu, M. Yusuf
    Nature becomes a source of inspiration to many researches on imaging systems. Imaging features owned by biological forms such as high resolution, wide field of view, high depth of field, high sensitivity to motion and light are attractive reasons to mimic the nature in imaging system applications. In this study, an arthropod eye's hexagonal shaped ommatidia are taken as a model for uncooled microbolometer pixel structure. A hexagonal pixel with 34 um diagonal length which has the thermal conductance value of 1.48x10(-7) W/K and the time constant value of 0.69 ms is designed for the first time in literature. The pixels are estimated to have an NETD of less than 250 mK in a potential 384x288 microbolometer array.
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    Pixel level vacuum packaging for single layer microbolometer detectors with on pixel lens
    (Slovak Univ Technology, 2022) Tanrikulu, M. Yusuf
    This paper presents a new approach for fabrication of single layer microbolometer detectors featuring pixel level vacuum packaging together with a lens on the pixel. The proposed lens structure can be used to increase the fill factor of the detector so that the pixel size can be decreased without decreasing the minimum feature size in the detector which is a problem in single layer microbolometers. The designs of the lens and the fabrication process of pixel level vacuum packaged microbolometer detector together with this lens are given in the framework of this study. The optical and mechanical simulations of the structure are performed. The radius of curvature of the lens is optimized to be 25 mu m and it is shown that the condensing efficiency is 100% for 3 mu m lens-detector distance. The deflection in the lens structure is found approximately as 0.8 nm in 1 atm environment pressure, showing that the proposed structure is durable. The proposed structure increases the fill factor to twice of the original value without decreasing the minimum feature size in the fabrication processes, resulting in the same amount of improvement in the performance of the detector. This approach can also be used to increase the yield and decrease the fabrication cost of single layer and also standard microbolometers with small pixel sizes, as it integrates the vacuum packaging in the fabrication steps.
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    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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    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.
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    Three-level microbolometer structures: design and absorption optimization
    (Spie-Soc Photo-Optical Instrumentation Engineers, 2013) Tanrikulu, M. Yusuf
    The design of two new three-level (3-L) microbolometer structures together with their absorption coefficient optimizations are reported. Three-level microbolometers are the detectors where three sacrificial layers are used during their fabrication process. They are needed to increase the performance of the microbolometer detectors when the lithography and etch-process capabilities of the fabrication facility are limited. Two new 3-L microbolometers are proposed and the absorption simulations of these detectors are performed using a cascaded transmission line model of the detectors. The thermal simulations of the proposed detectors are also done using CoventorWare FEM software. The absorption coefficient of the detectors can be as high as 92%, and their thermal conductance values can be as low as 2.4 x 10(-8) W/K depending on the type of the detector, resulting in an improvement of 50% on the NETD value when compared with a standard 2-L microbolometer structure fabricated using the same technology. The proposed detector structures can be used to decrease the need for high-process capabilities and make it possible to fabricate high-performance microbolometer detectors especially for universities and research centers. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)