@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{ReiterHanMaietal., author = {Reiter, Sebastian and Han, Weijia and Mai, Christian and Spirito, Davide and Jose, Josmy and Z{\"o}llner, Marvin Hartwig and Fursenko, Oksana and Schubert, Markus Andreas and Stemmler, Ivo and Wenger, Christian and Fischer, Inga Anita}, title = {Titanium Nitride Plasmonic Nanohole Arrays for CMOS-compatible integrated refractive index sensing: influence of layer thickness on optical properties}, series = {Plasmonics}, journal = {Plasmonics}, issn = {1557-1963}, doi = {10.1007/s11468-023-01810-3}, pages = {1 -- 13}, language = {en} } @misc{HanReiterSchlipfetal., author = {Han, Weijia and Reiter, Sebastian and Schlipf, Jon and Mai, Christian and Spirito, Davide and Jose, Josmy and Wenger, Christian and Fischer, Inga Anita}, title = {Strongly enhanced sensitivities of CMOS compatible plasmonic titanium nitride nanohole arrays for refractive index sensing under oblique incidence}, series = {Optics Express}, volume = {31}, journal = {Optics Express}, number = {11}, issn = {1094-4087}, doi = {10.1364/OE.481993}, pages = {17389 -- 17407}, abstract = {Titanium nitride (TiN) is a complementary metal-oxide-semiconductor (CMOS) compatible material with large potential for the fabrication of plasmonic structures suited for device integration. However, the comparatively large optical losses can be detrimental for application. This work reports a CMOS compatible TiN nanohole array (NHA) on top of a multilayer stack for potential use in integrated refractive index sensing with high sensitivities at wavelengths between 800 and 1500 nm. The stack, consisting of the TiN NHA on a silicon dioxide (SiO2) layer with Si as substrate (TiN NHA/SiO2/Si), is prepared using an industrial CMOS compatible process. The TiN NHA/SiO2/Si shows Fano resonances in reflectance spectra under oblique excitation, which are well reproduced by simulation using both finite difference time domain (FDTD) and rigorous coupled-wave analysis (RCWA) methods. The sensitivities derived from spectroscopic characterizations increase with the increasing incident angle and match well with the simulated sensitivities. Our systematic simulation-based investigation of the sensitivity of the TiN NHA/SiO2/Si stack under varied conditions reveals that very large sensitivities up to 2305 nm per refractive index unit (nm RIU-1) are predicted when the refractive index of superstrate is similar to that of the SiO2 layer. We analyze in detail how the interplay between plasmonic and photonic resonances such as surface plasmon polaritons (SPPs), localized surface plasmon resonances (LSPRs), Rayleigh Anomalies (RAs), and photonic microcavity modes (Fabry-P{\´e}rot resonances) contributes to this result. This work not only reveals the tunability of TiN nanostructures for plasmonic applications but also paves the way to explore efficient devices for sensing in broad conditions.}, language = {en} } @misc{ReiterRatzkeNitschetal., author = {Reiter, Sebastian and Ratzke, Markus and Nitsch, Paul-Gregor and Mai, Christian and Spirito, Davide and Corley-Wiciak, Agnieszka Anna and Wenger, Christian and Fischer, Inga A.}, title = {Optical response of titanium nitride plasmonic nanohole arrays : impact of square and hexagonal array geometry, pitch, and nanohole diameter}, series = {Plasmonics}, volume = {20}, journal = {Plasmonics}, publisher = {Springer}, address = {New York, NY}, doi = {10.1007/s11468-025-02934-4}, pages = {8825 -- 8834}, abstract = {Plasmonic nanohole arrays (NHAs) exhibit extraordinary optical transmission (EOT) evoked by resonant excitation of surface plasmons at an excitation wavelength, which is highly sensitive to changes in refractive index in the surrounding dielectric. This can enable the use of plasmonic NHAs in on-chip refractive index sensors. Such sensors can be realized on the cost-effective silicon platform by the integration of a plasmonic NHA and a Ge photodetector, provided that complementary metal-oxide-semiconductor (CMOS)-compatible materials are used for their fabrication. Titanium nitride (TiN) as a biocompatible and CMOS-compatible plasmonic transition metal nitride is well-suited for integration on the silicon platform; however, the comparatively large losses within the material require geometry optimization strategies in order to improve the optical properties of TiN NHAs for sensing. In this work, we investigated different TiN NHA geometries both in experiment and simulation. We extensively characterized square and hexagonal arrays with varying pitches and nanohole diameters and provide a detailed comparison of their optical properties. We also discuss characterization results for surface refractive index changes imposed by depositing a thin Al2O3 layer on top of the NHAs. While we do not observe a clear advantage of hexagonal arrays compared to square arrays for sensing, our results highlight the importance of geometry optimization for TiN NHAs integrated with devices.}, language = {en} } @misc{DoraiSwamyReddyPerezBaronietal., author = {Dorai Swamy Reddy, Keerthi and P{\´e}rez, Eduardo and Baroni, Andrea and Mahadevaiah, Mamathamba Kalishettyhalli and Marschmeyer, Steffen and Fraschke, Mirko and Lisker, Marco and Wenger, Christian and Mai, Andreas}, title = {Optimization of technology processes for enhanced CMOS-integrated 1T-1R RRAM device performance}, series = {The European Physical Journal B}, volume = {97}, journal = {The European Physical Journal B}, publisher = {Springer Science and Business Media LLC}, issn = {1434-6028}, doi = {10.1140/epjb/s10051-024-00821-1}, pages = {9}, abstract = {Implementing artificial synapses that emulate the synaptic behavior observed in the brain is one of the most critical requirements for neuromorphic computing. Resistive random-access memories (RRAM) have been proposed as a candidate for artificial synaptic devices. For this applicability, RRAM device performance depends on the technology used to fabricate the metal-insulator-metal (MIM) stack and the technology chosen for the selector device. To analyze these dependencies, the integrated RRAM devices in a 4k-bit array are studied on a 200 mm wafer scale in this work. The RRAM devices are integrated into two different CMOS transistor technologies of IHP, namely 250 nm and 130 nm and the devices are compared in terms of their pristine state current. The devices in 130 nm technology have shown lower number of high pristine state current devices per die in comparison to the 250 nm technology. For the 130 nm technology, the forming voltage is reduced due to the decrease of HfO2 dielectric thickness from 8 nm to 5 nm. Additionally, 5\% Al-doped 4 nm HfO2 dielectric displayed a similar reduction in forming voltage and a lower variation in the values. Finally, the multi-level switching between the dielectric layers in 250 nm and 130 nm technologies are compared, where 130 nm showed a more significant number of conductance levels of seven compared to only four levels observed in 250 nm technology.}, language = {en} } @misc{LukosiusLukoseLiskeretal., author = {Lukosius, Mindaugas and Lukose, Rasuolė and Lisker, Marco and Dubey, P. K. and Raju, A. I. and Capista, Daniele and Majnoon, Farnaz and Mai, A. and Wenger, Christian}, title = {Developments of Graphene devices in 200 mm CMOS pilot line}, series = {Proc. Nanotechnology Materials and Devices Conference (NMDC 2023),Paestum, Italy, 22-25 October 2023}, journal = {Proc. Nanotechnology Materials and Devices Conference (NMDC 2023),Paestum, Italy, 22-25 October 2023}, publisher = {Institute of Electrical and Electronics Engineers (IEEE)}, isbn = {979-8-3503-3546-0}, doi = {10.1109/NMDC57951.2023.10343569}, pages = {505 -- 506}, abstract = {Due to the unique electronic band structure, graphene has opened great potential to extend the functionality of a large variety of devices. Despite the significant progress in the fabrication of various graphene based microelectronic devices, the integration of graphene devices still lack the stability and compatibility with Si-technology processes. Therefore, the investigation and preparation of graphene devices in conditions resembling as close as possible the Si technology environment is of highest importance. This study aims to explore various aspects of graphene research on a 200mm pilot line, with a focus on simulations and fabrication of graphene modulator. To be more precise, it includes design and fabrication of the layouts, necessary mask sets, creation of the flows, fabrication, and measurements of the Gr modulators on 200 mm wafers.}, language = {en} } @misc{FuenningPaulManganellietal., author = {F{\"u}nning, Tabea and Paul, Martin and Manganelli, Costanza Lucia and Wenger, Christian and Mai, Andreas and Steglich, Patrick}, title = {Comparative simulation analysis of photonic ultrasound sensors based on silicon waveguides}, series = {Scientific reports}, volume = {15}, journal = {Scientific reports}, number = {1}, publisher = {Springer Science and Business Media LLC}, address = {[London]}, issn = {2045-2322}, doi = {10.1038/s41598-025-01953-9}, pages = {1 -- 13}, abstract = {Pressure sensors based on photonic integrated circuits (PIC) offer the prospect of outstanding sensitivities, extreme miniaturization and have the potential for highly scalable production using CMOS compatible processing. PIC-based pressure sensors detect the change in optical properties, i.e. the intensity or phase of the optical carrier wave inside miniaturized waveguide structures. The detection of ultrasound is achieved by engineering the waveguide architecture such that a pressure causes a high change in the effective refractive index of the waveguide. A range of PIC-based pressure sensors have been reported, but a comparison of the sensitivity of the different approaches is not straightforward, since different pressure sensitive waveguide architectures as well as photonic layouts and measurement setups impact the performance. Additionally, the used sensitivity unit is not uniform throughout the different studies, further complicating a comparison. In this work, a detailed simulation study is carried out by finite element modeling of different pressure sensitive waveguide architectures for a consistent comparison. We analyze three different sensor architectures: (A) a free standing membrane located within a tiny air gap above the waveguide, (B) a waveguide located on top of a deflectable membrane as well as (C) a waveguide embedded inside a pressure-sensitive polymer cladding. The mechanical response of the structures and the resulting changes in mode propagation, i.e. the change of the effective refractive index, are analyzed. The waveguide sensitivities in RIU/MPa for different waveguide types (strip, slot) and polarization states (TE, TM) are compared. The results reveal inherent limitations of the different waveguide designs and create a basis for the selection of suitable designs for further ultrasound sensor development. Possibilities for enhancing waveguide sensitivity are identified and discussed. Additionally, we have shown that the studied approaches are extensible to SiN waveguides.}, language = {en} }