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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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    THE EFFECT OF CRYSTAL STRUCTURE AND METAL ELECTRODES ON GAS DETECTION IN TiO2 NANOTUBES H2 SENSORS
    (International Association for Hydrogen Energy, IAHE, 2022) Tasyurek, Lutfi Bilal; Isik, Esme; Isik, Ibrahim; Kilinc, Necmettin
    In this study, the effects of various metal electrodes and various crystal structures on hydrogen (H2) gas sensors based on titanium dioxide (TiO2) nanotubes were investigated. For the production of TiO2 nanotubes, anodization method consisting of an electrolyte containing 0.5wt% NH4F in 85% pure glycerol solution was applied. Scanning electron microscope (SEM) images of the obtained TiO2 nanotubes were examined. In order to see the effect of different crystal structures of TiO2, amorphous, anatase and rutile phases were obtained by annealing of samples. Each of the Ti/TiO2 nanotubes/metal (Pd, Pt, Au, and Ag) gas sensors, obtained by coating with palladium (Pd), platinum (Pt), gold (Au) and silver (Ag) electrodes, was tested at room temperature at 1% H2 concentration depending on three different phases. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
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    The Structural and Electrical Characterization of Europium Sulfide Thin Films Prepared with E-Beam Evaporation †
    (Multidisciplinary Digital Publishing Institute (MDPI), 2023) Tasyurek, Lutfi Bilal; Dörr, Frowin; Erkovan, Mustafa; Shokr, Yasser A.; Kilinc, Necmettin; Fumagalli, Paul
    In this study, EuS thin films with varying thicknesses (15, 25, and 50 nm) were deposited onto a Si/SiO2 substrate using e-beam evaporation. Subsequently, two Ag contact electrodes with a 0.2 mm spacing were prepared via thermal evaporation using a shadow mask. To investigate the influence of film thickness and temperature on the electrical properties of EuS thin films, current-voltage (I–V) measurements were performed in a temperature range of 300–433 K for a voltage range of −2 V to +2 V. The I–V characteristics exhibited a temperature-dependent behavior, particularly showing an increase in current with rising temperature in the forward bias region. Furthermore, an improvement in the Schottky behavior was observed with increasing EuS film thickness. Additionally, the AC electrical and dielectric properties of the EuS thin film were examined in a frequency range of 4 Hz–8 MHz. Capacitance, conductance, impedance, and the Cole–Cole characteristic of EuS were analyzed in detail with respect to frequency, temperature, and film thicknesses. © 2023 by the authors.
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    Titanium nitride thin films grown by ion beam physical vapor deposition
    (Aip Publishing, 2025) Isik, Esme; Sterland, Dominic; Kilinc, Necmettin; Bell, Gavin R.
    A novel ion beam physical vapor deposition technique has been developed for TiN thin film deposition. The method uses only standard surface science tools, namely a cold cathode ion gun (normally used for sputter cleaning with Ar) operated with N2 gas and a modified titanium sublimation pump as a Ti PVD source. TiN thin films were deposited onto semi-insulating GaAs (001) substrates, and their physical and electrical properties were measured. X-ray photoelectron spectroscopy suggested predominantly TiN bonding with some oxynitride components. The DC conductivity increased in the range of 200-350 S/cm at temperatures ranging from 300 to 430 K. The behavior was consistent with the correlated barrier hopping model with an activation energy of 0.043 eV. The AC measurements (40 Hz to 0.2 MHz) indicated lower impedance above 10 kHz, possibly from the reduced effect of polarization at grain boundaries and other extended defects. The DC temperature dependence was also maintained even at the highest frequencies. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(https://creativecommons.org/licenses/by/4.0/).