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    Enhancing high sensitive hydrogen detection of Bi2O3 nanoparticle decorated TiO2 nanotubes
    (Elsevier Science Sa, 2024) Isik, Esme; Tasyurek, Lutfi Bilal; Tosun, Emir; Kilinc, Necmettin
    An electrochemical anodization technique was used to create a hydrogen gas sensor based on TiO2 nanotubes decorated with bismuth oxide (Bi2O3). Bismuth nitrate pentahydrate (Bi(NO3)3 center dot 5H2O) was employed as the source material for Bi2O3. The resulting nanotubes were annealed at 500 degrees C, revealing an amorphous structure with a mixed phase of rutile and anatase. Platinum (Pt) electrodes, with a thickness of 100 nm, were coated onto the Bi2O3@TiO2/Ti and TiO2/Ti structures for sensor testing. Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM) were used to examine the structural, morphological, and surface properties of the Bi2O3@TiO2 and TiO2 nanotubes. The hydrogen sensing properties of the Pt/Bi2O3@TiO2/Ti and Pt/TiO2/Ti devices were evaluated at room temperature, with hydrogen concentrations ranging from 1000 ppm to 10 %. The I-V characterization of the sensor devices under 1 % H2 exhibited typical Schottky-type behavior. Remarkably, the Pt/Bi2O3@TiO2/Ti structure demonstrated a sensor response 1 x 107 times higher than that of in a dry air environment when the same voltage was applied under up to 1 % H2 conditions. The uniform dispersion of Bi2O3 nanoparticles throughout the structure contributed to the enhanced sensor response in the presence of H2.
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    Enhancing the performance of TiO2 nanotube-based hydrogen sensors through crystal structure and metal electrode
    (Pergamon-Elsevier Science Ltd, 2024) Tasyurek, Lutfi Bilal; Isik, Esme; Isik, Ibrahim; Kilinc, Necmettin
    In this research, the effect of metal electrodes and crystalline phase on gas detection of titanium dioxide (TiO2) nanotube-based hydrogen (H2) sensors was investigated. TiO2 nanotubes were produced using glycerol-based electrolyte and annealed at 300 degrees C and 700 degrees C to change the anatase and rutile crystalline phases, respectively. TiO2 nanotubes were coated by platinum (Pt), palladium (Pd), gold (Au) and silver (Ag) electrodes to fabricate metal/TiO2 nanotubes Ti H2 sensor devices and then the current-voltage (I-V) characteristics were investigated at room temperature. The structural properties of TiO2 nanotubes were characterized by SEM, FE-SEM, XRD, and Raman techniques. The H2 detection properties of the sensors were examined at the 1000 ppm - 5% H2 concentration range. The crystal structure and metal electrodes are the main factors that affect the H2 sensing properties of TiO2 nanotube-based sensors. The effect of crystal forms on sensitivity was not the same as for metal electrodes. The underlying sensing mechanisms for different types of metal electrodes and crystal structures are discussed and the relevance of their sensing performance to nanotubes and electronic properties is investigated. In addition, discussion of each metal electrode and crystal structure will make important contributions to the development of H2 sensors. The Pd-coated device annealed at 700 degrees C showed the best detection performance.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Hydrogen detection and electrical properties of titanium silicate Schottky diode fabricated by RF-magnetron sputtering method
    (Pergamon-Elsevier Science Ltd, 2025) Tasyurek, Lutfi Bilal; Kilinc, Necmettin
    In this study, the electrical characterization of Schottky contact produced by coating TiSiO4 from the perovskite like layered family on p and n type Si by using RF-magnetron sputtering method was investigated depending on gas atmosphere and temperature. The morphological structure of the TiSiO4 thin film was examined by XRD analysis, FE-SEM images, and EDX spectrum. According to AFM images, the average roughness was found to be 0.811 nm. Temperature dependent I-V and AC characteristics of p-Si/TiSiO4 and n-Si/TiSiO4 devices were measured under dry air flow. In addition, frequency dependent C-V measurements of the devices were performed to investigate the capacitance properties of the scheelite-type interface. Also, the sensor response obtained with this device was as high as 267.7. Hydrogen sensing properties of p-Si/TiSiO4/Pt structure were investigated depending on concentration, temperature and interference gases. Electrical parameters with p type Si provided better results. The p-Si/TiSiO4/Pt sensor device showed Schottky behavior at low temperatures, but the device changed to ohmic behavior with increasing temperature.
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    Perovskite based hydrogen detection and electrical properties of n-Si/ BaTiO3 heterojunction
    (Pergamon-Elsevier Science Ltd, 2026) Tasyurek, Lutfi Bilal; Karakurt, Huseyin; Kilinc, Necmettin
    In this study, the electrical characterization of a heterojunction structure produced by coating powdered BaTiO3 from the perovskite family onto n-type silicon using the drop casting method was investigated at room temperature and as a function of temperature in a hydrogen atmosphere. The structural and optical characterization were evaluated using XRD analysis of the BaTiO3 powder, SEM - TEM images of the thin film structure, EDX spectrum, and UV analysis. The temperature-dependent current-voltage and alternating current changes of the nSi/BaTiO3 heterojunction were measured in a dry air atmosphere. According to the measurement results, the nSi/BaTiO3/Pt heterojunction device exhibited Schottky behavior. Furthermore, the sensor response of the heterojunction to hydrogen gas was calculated as 6.73. The hydrogen sensor response, measured at 50 degrees C at concentrations ranging from 500 ppm to 3%, increased in a concentration-dependent manner. Hydrogen detection measured at 100 degrees C shows a very good repeatability and stability at 20-min intervals in a 1% hydrogen atmosphere. The sensor response of n-Si/BaTiO3 heterojunction is about 3.71 +/- 4% in average for 70 days exposure to 1% hydrogen at 100 degrees C. Hydrogen gas tests were measured as a function of temperature and concentration changes. The obtained results are promising for the evaluation of the n-Si/BaTiO3 heterojunction as a hydrogen gas sensor.
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    Synthesis and analysis of TiO2 nanotubes by electrochemical anodization and machine learning method for hydrogen sensors
    (Elsevier, 2022) Isik, Esme; Tasyurek, Lutfi Bilal; Isik, Ibrahim; Kilinc, Necmettin
    The conductometric hydrogen gas sensors were used to explore TiO2 nanotubes in this study. TiO2 nanotubes are synthesized by anodization of the titanium foils using a neutral 0.5% and 1% (wt) NH4F in glycerol solution depending on anodization time and anodization voltage at the temperature of 20 degrees C. The amorphous, rutile and anatase phases of TiO2 are observed for as-prepared TiO2 nanotubes, annealed at 700 and 300 degrees C, respectively. The diameters of the nanotubes grow as the anodization time and voltage increase, according to scanning electron microscopy (SEM) images. The inner diameter of nanotubes is changed between similar to 70 nm to similar to 225 nm. Hydrogen sensing properties of Ti/TiO2 nanotubes/Pd device has been tested at room temperature under concertation range from 0.5% to 10% depending on the crystalline phase. The highest sensor response is observed for anatase crystalline TiO2 nanotubes. Typical Schottky-type behavior is observed from the I-V measurement. All the fabricated nanotube diameters are also simulated by using Support Vector Machine and Artificial Neural Network models. And also, some of the nanotube diameters which are not obtained experimentally (anodization voltage of 70 V) are estimated using the Support Vector Machine and Artificial Neural Network models. In addition, an analytical model is also proposed using Jacobi numeric analysis method alternative to the simulation model for the nanotube diameter. Finally, the analytical, simulation, and experimental results are compared, and the best result is obtained using the 1 Hidden Layer Artificial Neural Network model.
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    The synthesis of SrTiO3 nanocubes and the analysis of nearly ideal diode application of Ni/SrTiO3 nanocubes/n-Si heterojunctions
    (Iop Publishing Ltd, 2018) Tasyurek, Lutfi Bilal; Sevim, Melike; Caldiran, Zakir; Aydogan, Sakir; Metin, Onder
    A perovskite type of strontium titanate (SrTiO3) nanocubes (NCs) were synthesized by using a hydrothermal process and the thin films of these NCs were deposited on an n-type silicon wafer by spin coating technique. As-synthesized SrTiO3 NCs were characterized by transmission electron microscope, scanning electron microscope, energy dispersive x-ray, x-ray diffraction and Raman spectroscopy. After evaporation of 12 Ni dots on the SrTiO3 NCs thin films deposited on n-Si, the Ni/SrTiO3 NCs/n-Si heterojunction devices were fabricated for the first time. The ideality factors of the twelve fabricated devices were vary from 1.05 to 1.22 and the barrier height values varied from 0.64 to 0.68 eV. Furthermore, since all devices yielded similar characteristics, only the current-voltage and the capacitance-voltage of one selected device (named H1) were investigated in detailed. The series resistance of this device was calculated as 96 Omega.