@misc{ReiterSenguelMaietal., author = {Reiter, Sebastian and Seng{\"u}l, Akant and Mai, Christian and Spirito, Davide and Wenger, Christian and Fischer, Inga Anita}, title = {On-chip refractive index sensors based on plasmonic TiN Nanohole Arrays}, series = {2024 IEEE Silicon Photonics Conference (SiPhotonics)}, journal = {2024 IEEE Silicon Photonics Conference (SiPhotonics)}, isbn = {979-8-3503-9404-7}, issn = {1949-209X}, doi = {10.1109/SiPhotonics60897.2024.10544048}, pages = {2}, language = {de} } @misc{JoseMaiWengeretal., author = {Jose, Josmy and Mai, Christian and Wenger, Christian and Fischer, Inga Anita}, title = {Integration concept of plasmonic TiN nanohole arrays in a 200 mm BiCMOS Si technology for refractive index sensor applications}, series = {iCCC2024 - iCampµs Cottbus Conference}, journal = {iCCC2024 - iCampµs Cottbus Conference}, doi = {10.5162/iCCC2024/7.2}, pages = {96 -- 99}, language = {de} } @misc{MaiPeczekKrohetal., author = {Mai, Christian and Peczek, Anna and Kroh, Aleksandra and Jose, Josmy and Reiter, Sebastian and Wenger, Christian and Fischer, Inga Anita}, title = {Towards a CMOS compatible refractive index sensor: cointegration of TiN nanohole arrays and Ge photodetectors in a 200 mm wafer silicon technology}, series = {Optics Express}, volume = {32}, journal = {Optics Express}, number = {17}, publisher = {Optica Publishing Group}, issn = {1094-4087}, doi = {10.1364/OE.530081}, pages = {29099 -- 29111}, abstract = {In this work, we present the monolithic integration of a TiN nanohole array and a Ge photodetector towards a CMOS compatible fabrication of a refractive index sensor in a 200 mm wafer silicon technology. We developed a technology process that enables fabrication with high yields of around 90\%. Ge photodetectors with a Ge layer thickness of 450 nm and an area of 1600 µm2 (40 µm x 40 µm) show dark current densities of around 129 mA/cm2 and responsivities of 0.114 A/W measured by top illumination (TE polarization; λ = 1310 nm; angle of incidence = 14 °) at a reverse bias of 1 V. Nanohole arrays were structured in a 150 nm thick TiN layer. They were integrated into the back end of line and placed spatially close to the Ge photodetectors. After the metallization, passivation, and pad opening, the nanohole arrays were released with the help of an amorphous silicon stop layer. A significant impact of the TiN nanohole arrays on the optical behavior of the photodetector could be proven on the wafer level. Photocurrent measurements by top illumination confirm a strong dependence of optical properties on the polarization of the incident light and the nanohole array design. We demonstrate very stable photocurrents on the wafer level with a standard deviation of σ \< 6\%.}, 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{WeisshauptSuergersBloosetal., author = {Weißhaupt, David and S{\"u}rgers, Christoph and Bloos, Dominik and Funk, Hannes Simon and Oehme, Michael and Fischer, Gerda and Schubert, Markus Andreas and Wenger, Christian and van Slageren, Joris and Fischer, Inga Anita and Schulze, J{\"o}rg}, title = {Lateral Mn5Ge3 spin-valve in contact with a high-mobility Ge two-dimensional hole gas}, series = {Semiconductor Science and Technology}, volume = {39}, journal = {Semiconductor Science and Technology}, number = {12}, publisher = {IOP Publishing}, issn = {0268-1242}, doi = {10.1088/1361-6641/ad8d06}, pages = {1 -- 10}, abstract = {Abstract Ge two-dimensional hole gases (2DHG) in strained modulation-doped quantum-wells represent a promising material platform for future spintronic applications due to their excellent spin transport properties and the theoretical possibility of efficient spin manipulation. Due to the continuous development of epitaxial growth recipes extreme high hole mobilities and low effective masses can be achieved, promising an efficient spin transport. Furthermore, the Ge 2DHG can be integrated in the well-established industrial complementary metal-oxide-semiconductor (CMOS) devices technology. However, efficient electrical spin injection into a Ge 2DHG—an essential prerequisite for the realization of spintronic devices—has not yet been demonstrated. In this work, we report the fabrication and low-temperature magnetoresistance (MR) measurements of a laterally structured Mn5Ge3/Ge 2DHG/ Mn5Ge3 device. The ferromagnetic Mn5Ge3 contacts are grown directly into the Ge quantum well by means of an interdiffusion process with a spacing of approximately 130 nm, forming a direct electrical contact between the ferromagnetic metal and the Ge 2DHG. Here, we report for the first time a clear MR signal for temperatures below 13 K possibly arising from successful spin injection into the high mobility Ge 2DHG. The results represent a step forward toward the realization of CMOS compatible spintronic devices based on a 2DHG.}, 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} } @misc{HayatRatzkeAlvaradoChavarinetal., author = {Hayat, Ahsan and Ratzke, Markus and Alvarado Chavarin, Carlos and Z{\"o}llner, Marvin Hartwig and Corley-Wiciak, Agnieszka Anna and Schubert, Markus Andreas and Wenger, Christian and Fischer, Inga Anita}, title = {Structural and morphological properties of CeO2 films deposited by radio frequency magnetron sputtering for back-end-of-line integration}, series = {Thin Solid Films}, volume = {807}, journal = {Thin Solid Films}, issn = {0040-6090}, doi = {10.1016/j.tsf.2024.140547}, pages = {3}, language = {en} }