TY - GEN A1 - Kotwica, Tomasz A1 - Domaradzki, Jarosław A1 - Wojcieszak, Damian A1 - Sikora, Andrzej A1 - Kot, Małgorzata A1 - Schmeißer, Dieter T1 - Analysis of surface properties of Ti-Cu-Ox gradient thin films using AFM and XPS investigations T2 - Materials Science-Poland N2 - The paper presents results of investigations on surface properties of transparent semiconducting thin films based on (Ti-Cu)oxide system prepared using multi-magnetron sputtering system. The thin films were prepared using two programmed profiles of pulse widt hmodulation coefficient, so called V- and U-shape profiles. The applied powering profiles allowed fabrication of thin films with gradient distribution of Ti and Cu elements over the thickness of deposited layers. Optical investigations allowed determination of transparency of prepared films that reached up to 60 % in the visible part of optical radiation, which makes them attractive for the transparent electronics domain. Surface properties investigations showed that the surface of mixed (Ti-Cu)oxides was sensitive to adsorption, in particular to carbon dioxide and water vapor. Soft etching with argon ions resulted in surface cleaning from residuals, however, deoxidation of Cu-oxide components was also observed. KW - surface KW - gradient distribution KW - thin film oxide Y1 - 2019 U6 - https://doi.org/10.2478/msp-2018-0100 SN - 0137-1339 SN - 2083-1331 SN - 2083-134X VL - 36 IS - 4 SP - 761 EP - 768 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 - 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 - 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 - 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 -