TY - GEN A1 - Kosto, Yuliia A1 - Kapuscik, Paulina A1 - Tschammer, Rudi A1 - Guttmann, Dominic A1 - Mankowska, Ewa A1 - Matvija, Peter A1 - Morales, Carlos A1 - Mazur, Michał A1 - Henkel, Karsten A1 - Matolinova, Iva A1 - Domaradzki, Jarosław A1 - Flege, Jan Ingo T1 - Bare and Pd-doped ceria thin films prepared by ALD and EBE for hydrogen detection T2 - Verhandlungen der DPG N2 - The need to store and use hydrogen safely as part of green economy based on renewable energy evokes a necessity to reliably detect it at ambient conditions. The majority of currently used sensors are working at elevated temperatures (200-500 °C). In this work, we demonstrate that ceria films deposited on a commercial electrode by atomic layer deposition (ALD) and electron beam evaporation (EBE) electrically respond to hydrogen (from 20 to 500 ppm) at much lower temperatures (50-200 °C). The results reveal that <1.5 nm thin Pd adlayer increases the electrical response by several orders of magnitude for both ceria films. The NAP-XPS study under changing oxidative/reductive atmospheres sheds light on the mechanism of Pd-CeOx thermal activation and the role of the deposition technique in the reactivity of the oxide. KW - Hydrogen sensor KW - Atomic layer deposition (ALD) KW - ceria KW - Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) Y1 - 2024 UR - https://www.dpg-verhandlungen.de/year/2024/conference/berlin/part/o/session/59/contribution/5 SN - 0420-0195 PB - Deutsche Physikalische Gesellschaft CY - Bad Honnef ER - TY - GEN A1 - Kapuścik, Paulina A1 - Wojcieszak, Damian A1 - Pokora, Patrycja A1 - Mańkowska, Ewa A1 - Domaradzki, Jarosław A1 - Mazur, Michał A1 - Mazur, Piotr A1 - Kosto, Yuliia A1 - Morales, Carlos A1 - Kot, Małgorzata A1 - Flege, Jan Ingo T1 - Low temperature hydrogen sensor with high sensitivity based on CeOx thin film T2 - Sensors and Actuators B: Chemical N2 - In this work, a 500 nm-thick cerium oxide thin film was prepared by electron beam evaporation. It was found that the deposition of 7 nm thick Pd catalyst was required for obtaining a sensor response to hydrogen. The Pd/CeOx sensing structure has a high response of 5000 towards 25 ppm H2 at a working temperature of 200 °C and exhibits a sensor response of 1.3 at temperatures near ambient. Furthermore, the sensing structure exhibited excellent response/recovery kinetics. The results confirm that the CeOx-based materials are a promising material for the fabrication of room-temperature hydrogen sensors. KW - Cerium oxide KW - Thin film KW - Hydrogen sensing KW - Low operating temperature Y1 - 2024 U6 - https://doi.org/10.1016/j.snb.2024.136148 SN - 0925-4005 VL - 417 PB - Elsevier BV ER - TY - GEN A1 - Mazur, Michał A1 - Kapuścik, Paulina A1 - Weichbrodt, Wiktoria A1 - Domaradzki, Jarosław A1 - Mazur, Piotr A1 - Kot, Małgorzata A1 - Flege, Jan Ingo T1 - WO3 Thin-Film Optical Gas Sensors Based on Gasochromic Effect towards Low Hydrogen Concentrations T2 - Materials N2 - Hydrogen gas sensors have recently attracted increased interest due to the explosive nature of H2 and its strategic importance in the sustainable global energy system. In this paper, the tungsten oxide thin films deposited by innovative gas impulse magnetron sputtering have been investigated in terms of their response to H2. It was found that the most favourable annealing temperature in terms of sensor response value, as well as response and recovery times, was achieved at 673 K. This annealing process caused a change in the WO3 cross-section morphology from a featureless and homogenous form to a rather columnar one, but still maintaining the same surface homogeneity. In addition to that, the full-phase transition from an amorphous to nanocrystalline form occurred with a crystallite size of 23 nm. It was found that the sensor response to only 25 ppm of H2 was equal to 6.3, which is one of the best results presented in the literature so far of WO3 optical gas sensors based on a gasochromic effect. Moreover, the results of the gasochromic effect were correlated with the changes in the extinction coefficient and the concentration of the free charge carriers, which is also a novel approach to the understanding of the gasochromic phenomenon. KW - Tungsten oxide (WO3) KW - gas impulse magnetron sputtering KW - thin film KW - gasochromic properties KW - optical properties KW - annealing KW - optical hydrogen gas sensor Y1 - 2023 U6 - https://doi.org/10.3390/ma16103831 SN - 1996-1944 VL - 16 IS - 10 ER - TY - GEN A1 - Morales, Carlos A1 - Tschammer, Rudi A1 - Pożarowska, Emilia A1 - Kosto, Julia A1 - Villar‐Garcia, Ignacio J. A1 - Pérez‐Dieste, Virginia A1 - Favaro, Marco A1 - Starr, David E. A1 - Kapuścik, Paulina A1 - Mazur, Michał A1 - Wojcieszak, Damian A1 - Domaradzki, Jarosław A1 - Alvarado, Carlos A1 - Wenger, Christian A1 - Henkel, Karsten A1 - Flege, Jan Ingo T1 - Hydrogen sensing via heterolytic H₂ activation at room temperature by atomic layer deposited ceria T2 - ChemSusChem : chemistry, sustainability, energy, materials N2 - Ultrathin atomic layer deposited ceria films (<20 nm) are capable of H2 heterolytic activation at room temperature, undergoing a significant reduction regardless of the absolute pressure, as measured under in‐situ conditions by near ambient pressure X‐ray photoelectron spectroscopy. ALD‐ceria can gradually reduce as a function of H2 concentration under H2/O2 environments, especially for diluted mixtures below 10 %. At room temperature, this reduction is limited to the surface region, where the hydroxylation of the ceria surface induces a charge transfer towards the ceria matrix, reducing Ce4+ cations to Ce3+. Thus, ALD‐ceria replicates the expected sensing mechanism of metal oxides at low temperatures without using any noble metal decorating the oxide surface to enhance H2 dissociation. The intrinsic defects of the ALD deposit seem to play a crucial role since the post‐annealing process capable of healing these defects leads to decreased film reactivity. The sensing behavior was successfully demonstrated in sensor test structures by resistance changes towards low concentrations of H2 at low operating temperatures without using noble metals. These promising results call for combining ALD‐ceria with more conductive metal oxides, taking advantage of the charge transfer at the interface and thus modifying the depletion layer formed at the heterojunction. KW - Atomic Layer Deposition KW - Ceria KW - Hydrogen Sensing KW - X-Ray photoelectron spectroscopy KW - Raman spectroscopy KW - Resitive sensor Y1 - 2025 U6 - https://doi.org/10.1002/cssc.202402342 SN - 1864-5631 VL - 18 IS - 13 SP - 1 EP - 13 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Kapuścik, Paulina A1 - Domaradzki, Jarosław A1 - Obstarczyk, Agata A1 - Kot, Małgorzata A1 - Flege, Jan Ingo A1 - Keel, Emma A1 - Gibson, Des A1 - Wojcieszak, Damian T1 - Correlation between electron beam evaporation conditions and sensor response of cerium oxide coatings T2 - International journal of hydrogen energy N2 - Cerium oxide thin films were prepared by electron beam evaporation (EBE) under three deposition conditions: standard process, substrate heating at 200 °C, and ion beam assisted deposition (IBAD). The high optical transparency of the PVD-prepared coatings enables integration with transparent microelectronic devices, an aspect seldom explored in ceria-based gas sensors. Raman and optical analyses revealed various levels of oxygen vacancy-related defects in all films. Gas sensing measurements of the Pd/CeOx structures were correlated with their structural and electronic characteristics, including changes in Ce4+/Ce3+ ratios and band alignment during exposure to reducing gases, providing insight into the redox-driven sensing mechanism. All structures exhibit high ethanol sensitivity, while the highest response achieved for the films deposited with substrate heating and IBAD is consistent with their larger defect density and modified morphology. These findings demonstrate that tailoring EBE conditions provides an effective route to optimize CeOx thin films for improved gas sensing performance. KW - Cerium oxide KW - Thin film KW - Electron beam evaporation KW - Ion beam assisted deposition KW - Gas sensing Y1 - 2026 U6 - https://doi.org/10.1016/j.ijhydene.2026.154101 SN - 0360-3199 VL - 220 PB - Elsevier BV CY - Amsterdam ER -