@misc{KalraAlvaradoChavarinNitschetal., author = {Kalra, Amanpreet and Alvarado Chavarin, Carlos and Nitsch, Paul-Gregor and Tschammer, Rudi and Flege, Jan Ingo and Ratzke, Markus and Zoellner, Marvin Hartwig and Schubert, Markus Andreas and Wenger, Christian and Fischer, Inga Anita}, title = {Deposition of CeOₓ/SnOₓ-based thin films via RF magnetron sputtering for resistive gas sensing applications}, series = {Physica B, Condensed matter}, volume = {723}, journal = {Physica B, Condensed matter}, publisher = {Elsevier BV}, address = {Amsterdam}, issn = {0921-4526}, doi = {10.1016/j.physb.2025.418098}, pages = {1 -- 7}, abstract = {Cerium oxide-tin oxide (CeOx/SnOx) thin films with varying Sn content were deposited using RF magnetron sputtering and investigated for hydrogen sensing applications. Structural, compositional, and morphological properties were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). Gas sensing measurements showed effective hydrogen detection at room temperature, with the sensitivity strongly influenced by Sn content and oxygen vacancy concentration. Higher Sn concentration enhanced the sensing response, which was correlated with microstructural features obtained from AFM and EDX, as well as with the presence of Ce3+ and Ce4+ oxidation states identified by XPS. This study highlights the potential of CeOx/SnOx thin films for possible back-end-of-line integration and provides proof-of-principle for room-temperature hydrogen sensing.}, language = {en} } @misc{MuellerGoryachkoBurkovetal., author = {M{\"u}ller, Klaus and Goryachko, Andriy and Burkov, Yevgen and Schwiertz, Carola and Ratzke, Markus and K{\"o}ble, J. and Reif, J{\"u}rgen and Schmeißer, Dieter}, title = {Scanning Kelvin Probe Microscopy and Photoemission electron microscopy of organic source-drain structures}, series = {Synthetic Metals}, volume = {146}, journal = {Synthetic Metals}, number = {3}, issn = {0379-6779}, pages = {377 -- 382}, abstract = {n order to optimize organic field effect transistors (OFETs), the characterisation of active-layer surfaces in terms of their roughness, chemical composition and distribution of surface potentials is important. We report on high-resolution microscopic mapping of organic source-drain structures with P3HT as the semiconductor by scanning Kelvin probe microscopy (SKPM) and photoemission electron microscopy (PEEM). It was shown that PEEM is able to characterise the surface morphology (roughness), the chemical homogeneity and the composition of organic structures. The two-dimensional mapping of surface potentials by SKPM with applied source-drain voltages is shown to be an important ingredient of OFETs failure mode analysis.}, language = {en} } @misc{NitschRatzkePozarowskaetal., author = {Nitsch, Paul-G. and Ratzke, Markus and Pozarowska, Emilia and Flege, Jan Ingo and Alvarado Chavarin, Carlos and Wenger, Christian and Fischer, Inga Anita}, title = {Deposition of reduced ceria thin films by reactive magnetron sputtering for the development of a resistive gas sensor}, series = {Verhandlungen der DPG, Berlin 2024}, journal = {Verhandlungen der DPG, Berlin 2024}, publisher = {Deutsche Physikalische Gesellschaft}, address = {Bad Honnef}, issn = {0420-0195}, abstract = {The use of cerium oxide for hydrogen sensing is limited by the low electrical conductivity of layers deposited from a ceria target. To increase the electrical conductivity, partially reduced cerium oxide layers were obtained from a metallic cerium target by reactive magnetron sputtering. The proportions of the oxidation states Ce3+, present in reduced species, and Ce4+, present in fully oxidized species, were determined by ex-situ XPS. For electrical characterization, films were deposited on planarized tungsten finger electrodes. IV curves were measured over several days to investigate possible influences of oxygen and humidity on electrical conductivity. The morphological stability of the layers under ambient conditions was investigated by microscopical methods. The XPS results show a significant amount of Ce3+ in the layers. The electrical conductivity of as-grown samples is several orders of magnitude higher than that of samples grown from a ceria target. However, the conductivity decreases over time, indicating an oxidation of the layers. The surface morphology of the samples was found to be changing drastically within days, leading to partial delamination.}, language = {en} } @misc{KostoTschammerMoralesetal., author = {Kosto, Yuliia and Tschammer, Rudi and Morales, Carlos and Henkel, Karsten and Flege, Jan Ingo and Ratzke, Markus and Fischer, Inga Anita and Costina, Ioan and Alvarado Chavarin, Carlos and Wenger, Christian}, title = {Rational design and development of room temperature hydrogen sensors compatible with CMOS technology: a necessary step for the coming renewable hydrogen economy}, series = {Proceedings of iCampus Conference Cottbus 2024}, journal = {Proceedings of iCampus Conference Cottbus 2024}, publisher = {AMA Service GmbH}, address = {Wunstorf}, isbn = {978-3-910600-00-3}, doi = {10.5162/iCCC2024/P21}, pages = {182 -- 185}, abstract = {The transition towards a new, renewable energy system based on green energy vectors, such as hydrogen, requires not only direct energy conversion and storage systems, but also the development of auxiliary components, such as highly sensitive hydrogen gas sensors integrated into mass devices that operate at ambient conditions. Despite the recent advances in nanostructured metal oxide thin films in terms of simple fabrication processes and compatibility with integrated circuits, high sensitivity, and short response/recovery times usually require the use of expensive noble metals or elevated tem-peratures (>250 ºC), which results in high power consumption and poor long-term stability. This article presents the first steps of the work on developing a novel resistive hydrogen gas sensor based on ultrathin cerium oxide films, compatible with complementary metal oxide semiconductor technology and capable of operating at room temperature. Here, we show a multidisciplinary bottom-up approach combining different work areas for the sensor development, such as sensor architecture, sensing mechanism and deposition strategy of the active layer, electrical contact design depending on the desired electrical output, and fast testing under controlled environments.}, language = {en} }