TY - GEN A1 - Mańkowska, Ewa A1 - Mazur, Michał A1 - Domaradzki, Jarosław A1 - Mazur, Piotr A1 - Kot, Małgorzata A1 - Flege, Jan Ingo T1 - Hydrogen Gas Sensing Properties of Mixed Copper–Titanium Oxide Thin Films T2 - Sensors N2 - Hydrogen is an efficient source of clean and environmentally friendly energy. However, because it is explosive at concentrations higher than 4%, safety issues are a great concern. As its applications are extended, the need for the production of reliable monitoring systems is urgent. In this work, mixed copper–titanium oxide ((CuTi)Ox) thin films with various copper concentrations (0–100 at.%), deposited by magnetron sputtering and annealed at 473 K, were investigated as a prospective hydrogen gas sensing material. Scanning electron microscopy was applied to determine the morphology of the thin films. Their structure and chemical composition were investigated by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The prepared films were nanocrystalline mixtures of metallic copper, cuprous oxide, and titanium anatase in the bulk, whereas at the surface only cupric oxide was found. In comparison to the literature, the (CuTi)Ox thin films already showed a sensor response to hydrogen at a relatively low operating temperature of 473 K without using any extra catalyst. The best sensor response and sensitivity to hydrogen gas were found in the mixed copper–titanium oxides containing similar atomic concentrations of both metals, i.e., 41/59 and 56/44 of Cu/Ti. Most probably, this effect is related to their similar morphology and to the simultaneous presence of Cu and Cu2O crystals in these mixed oxide films. In particular, the studies of surface oxidation state revealed that it was the same for all annealed films and consisted only of CuO. However, in view of their crystalline structure, they consisted of Cu and Cu2O nanocrystals in the thin film volume. KW - mixed copper–titanium oxides KW - Cu2O KW - TiO2 KW - (CuTi)Ox KW - hydrogen gas sensing KW - thin films KW - magnetron sputtering Y1 - 2023 U6 - https://doi.org/10.3390/s23083822 SN - 1424-8220 VL - 23 IS - 8 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 - Obstarczyk, Agata A1 - Kaczmarek, Danuta A1 - Wojcieszak, Damian A1 - Mazur, Michał A1 - Domaradzki, Jarosław A1 - Kotwica, Tomasz A1 - Pastuszek, Roman A1 - Schmeißer, Dieter A1 - Mazur, Piotr A1 - Kot, Małgorzata T1 - Tailoring optical and electrical properties of thin-film coatings based on mixed Hf and Ti oxides for optoelectronic application T2 - Materials and Design N2 - In this work multi-magnetron sputtering stand was used for the deposition of the mixed oxides thin films based on HfO2 and TiO2. In order to obtain various material composition the power released to each magnetron (containing metallic hafnium and titanium targets) was precisely selected. Structural, surface, optical, electrical and mechanical properties of as-deposited coatings were analyzed. Depending on the hafnium content in the deposited thin films various types of the microstructure was obtained, i.e. HfO2-monoclinic, amorphous and TiO2-rutile. Increase of Ti content above 28 at. % in the as-prepared mixed oxides coatings caused their amorphization. It was found that with an increase of Ti content in prepared coatings their surface roughness and simultaneously water contact angle decreased. Performed measurements of electrical properties revealed that the lowest leakage current density in the range of 10−7 – 10−8 A/cm2 was obtained for amorphous coatings. Moreover, the tailoring of the dielectric constant was possible by a proper selection of material composition and microstructure of the deposited thin films. Average transparency in the visible wavelength region was in the range of ca. 79–86%. The influence of material composition and structure on shifting of the fundamental absorption edge and optical bandgap energy was also observed. The refractive index increased with an increase of Ti content, while extinction coefficient was the lowest for amorphous coatings. Additionally, hardness values were dependent on the material composition and optical packing density and were in the range from 7.6 GPa to 10.1 GPa. KW - Magnetron sputtering KW - Optical coatings KW - Electrical properties KW - Mixed oxides KW - HfO2 KW - TiO2 KW - High-k oxides KW - Amorphous thin films Y1 - 2019 U6 - https://doi.org/10.1016/j.matdes.2019.107822 SN - 0264-1275 VL - 175 ER - 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 -