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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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    Öğe
    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.