@misc{SkibitzkiCapelliniYamamotoetal.,
author = {Skibitzki, Oliver and Capellini, Giovanni and Yamamoto, Yuji and Zaumseil, Peter and Schubert, Markus Andreas and Schr{\"o}der, Thomas and Ballabio, Andrea and Bergamaschini, Roberto and Salvalaglio, Marco and Miglio, Leo and Montalenti, Francesco},
title = {RP-CVD growth of isolated Ge crystals and suspended layers on micrometric Si pillars},
series = {ACS Applied Materials and Interfaces},
volume = {8},
journal = {ACS Applied Materials and Interfaces},
number = {39},
issn = {1944-8244},
doi = {10.1021/acsami.6b07694},
pages = {26374 -- 26380},
language = {en}
}
@misc{SchlykowKlesseNiuetal.,
author = {Schlykow, Viktoria and Klesse, Wolfgang Matthias and Niu, Gang and Taoka, Noriyuki and Yamamoto, Yuji and Skibitzki, Oliver and Barget, M. R. and Zaumseil, Peter and K{\"a}nel, Hans von and Schubert, Markus Andreas and Capellini, Giovanni and Schroeder, Thomas},
title = {Selective growth of fully relaxed GeSn nano-islands by nanoheteroepitaxy on patterned Si(001)},
series = {Applied Physics Letters},
volume = {109},
journal = {Applied Physics Letters},
number = {20},
issn = {1077-3118},
doi = {10.1063/1.4967500},
pages = {202102},
language = {en}
}
@misc{LukosiusDabrowskiLiskeretal.,
author = {Lukosius, Mindaugas and Dabrowski, Jarek Marek and Lisker, Marco and Kitzmann, Julia and Schulze, Sebastian and Lippert, Gunther and Fursenko, Oksana and Yamamoto, Yuji and Schubert, Markus Andreas and Krause, Hans-Michael and Wolff, Andre and Mai, A. and Schr{\"o}der, Thomas and Lupina, Grzegorz},
title = {Metal-free, CVD Graphene synthesis on 200 mm Ge / Si(001) substrates},
series = {ACS Applied Materials and Interfaces},
volume = {8},
journal = {ACS Applied Materials and Interfaces},
number = {49},
issn = {1944-8244},
doi = {10.1021/acsami.6b11397},
pages = {33786 -- 33793},
language = {en}
}
@misc{GrzelaCapelliniKoczorowskietal.,
author = {Grzela, Tomasz and Capellini, Giovanni and Koczorowski, Wojciech and Schubert, Markus Andreas and Czajka, Ryszard and Curson, Neil J. and Heidmann, Inga and Schmidt, Thomas and Falta, Jens and Schr{\"o}der, Thomas},
title = {Growth and evolution of nickel - germanide nanonstructures on Ge(001)},
series = {Nanotechnology},
volume = {26},
journal = {Nanotechnology},
number = {38},
issn = {1361-6528},
pages = {385701},
language = {en}
}
@misc{MoralesMahmoodinezhadSchubertetal.,
author = {Morales, Carlos and Mahmoodinezhad, Ali and Schubert, Andreas Markus and Wenger, Christian and Henkel, Karsten and Flege, Jan Ingo},
title = {Functional ultra-thin oxide films deposited by atomic layer deposition on structured substrates},
series = {Verhandlungen der DPG - SurfaceScience21},
volume = {2021},
journal = {Verhandlungen der DPG - SurfaceScience21},
publisher = {Deutsche Physikalische Gesellschaft e.V.},
address = {Bad Honnef},
abstract = {In the last decades, atomic layer deposition (ALD) has gained prominence in the materials and surface science communities owing to its high potential for integration as a scalable process in microelectronics. ALD's largest strengths are its well-controlled layer-by-layer deposition and growth conformity on 3D structures. Yet, the ALD technique is also well known to lead to amorphous and defective, non-stoichiometric thin films, resulting in modified materials properties that may even preferentially be used in certain applications. To study these issues, we have developed an in-situ ALD reactor attached to an X-ray photoelectron spectroscopy (XPS) system, capable of switching between both pump and flow-type operation. This novel tool allows to cover the entire range of compounds and recipes used in ALD, thus clarifying the role of such defects at different deposition stages, growth conditions and film/substrate interfaces. To exemplify these sorts of studies, we show the deposition of Al2O3 5-10 nm films on nanostructured Si, and their use as substrates for functional CeOx ALD deposits.},
language = {en}
}
@misc{PerezBoschQuesadaRomeroZalizPerezetal.,
author = {P{\´e}rez-Bosch Quesada, Emilio and Romero-Zaliz, Roc{\´i}o and P{\´e}rez, Eduardo and Mahadevaiah, Mamathamba Kalishettyhalli and Reuben, John and Schubert, Markus Andreas and Jim{\´e}nez-Molinos, Francisco and Rold{\´a}n, Juan Bautista and Wenger, Christian},
title = {Toward Reliable Compact Modeling of Multilevel 1T-1R RRAM Devices for Neuromorphic Systems},
series = {Electronics (MDPI)},
volume = {10},
journal = {Electronics (MDPI)},
number = {6},
issn = {2079-9292},
doi = {10.3390/electronics10060645},
pages = {13},
abstract = {In this work, three different RRAM compact models implemented in Verilog-A are analyzed and evaluated in order to reproduce the multilevel approach based on the switching capability of experimental devices. These models are integrated in 1T-1R cells to control their analog behavior by means of the compliance current imposed by the NMOS select transistor. Four different resistance levels are simulated and assessed with experimental verification to account for their multilevel capability. Further, an Artificial Neural Network study is carried out to evaluate in a real scenario the viability of the multilevel approach under study.},
language = {en}
}
@misc{FranckDabrowskiSchubertetal.,
author = {Franck, Max and Dabrowski, Jaroslaw and Schubert, Markus Andreas and Wenger, Christian and Lukosius, Mindaugas},
title = {Towards the Growth of Hexagonal Boron Nitride on Ge(001)/Si Substrates by Chemical Vapor Deposition},
series = {Nanomaterials},
volume = {12},
journal = {Nanomaterials},
number = {19},
issn = {2079-4991},
doi = {10.3390/nano12193260},
abstract = {The growth of hexagonal boron nitride (hBN) on epitaxial Ge(001)/Si substrates via high-vacuum chemical vapor deposition from borazine is investigated for the first time in a systematic manner. The influences of the process pressure and growth temperature in the range of 10-7-10-3 mbar and 900-980 °C, respectively, are evaluated with respect to morphology, growth rate, and crystalline quality of the hBN films. At 900 °C, nanocrystalline hBN films with a lateral crystallite size of ~2-3 nm are obtained and confirmed by high-resolution transmission electron microscopy images. X-ray photoelectron spectroscopy confirms an atomic N:B ratio of 1 ± 0.1. A three-dimensional growth mode is observed by atomic force microscopy. Increasing the process pressure in the reactor mainly affects the growth rate, with only slight effects on crystalline quality and none on the principle growth mode. Growth of hBN at 980 °C increases the average crystallite size and leads to the formation of 3-10 well-oriented, vertically stacked layers of hBN on the Ge surface. Exploratory ab initio density functional theory simulations indicate that hBN edges are saturated by hydrogen, and it is proposed that partial de-saturation by H radicals produced on hot parts of the set-up is responsible for the growth},
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{FritscherUhlmannOstrovskyyetal.,
author = {Fritscher, Markus and Uhlmann, Max and Ostrovskyy, Philip and Reiser, Daniel and Chen, Junchao and Schubert, Andreas and Schulze, Carsten and Kahmen, Gerhard and Fey, Dietmar and Reichenbach, Marc and Krstic, Milos and Wenger, Christian},
title = {Area-efficient digital design using RRAM-CMOS standard cells},
series = {2024 IEEE Computer Society Annual Symposium on VLSI (ISVLSI)},
volume = {18},
journal = {2024 IEEE Computer Society Annual Symposium on VLSI (ISVLSI)},
publisher = {IEEE},
isbn = {979-8-3503-5411-9},
issn = {2159-3477},
doi = {10.1109/ISVLSI61997.2024.00026},
pages = {81 -- 87},
abstract = {Extending the scalability of digital integrated circuits through novel device concepts is an attractive option. Among these concepts, resistive random access memory (RRAM) devices allow fast and nonvolatile operation. However, building large memristive systems is still challenging since large analog circuits have to be designed and integrated. In this paper, we propose a novel solution - the implementation of digital standard cells by the means of RRAM devices. While this methodology is universal, with applications ranging from few-device-circuits to large macroblocks, we demonstrate it for a 2T2R-cell. The benefits of using RRAM devices are demonstrated by implementing a NAND standard cell merely consuming the area of two transistors. This cell is about 25 \% smaller than the equivalent CMOS NAND in the same technology. We use these cells to implement a half adder, beating the area of the equivalent CMOS implementation using more sophisticates gates by 15 \%. Lastly, we fully integrate this novel standard cell into a digital standard cell library and perform a synthesis and layout of a RISC-V CPU core.},
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{MoralesMahmoodinezhadTschammeretal.,
author = {Morales, Carlos and Mahmoodinezhad, Ali and Tschammer, Rudi and Kosto, Yuliia and Alvarado Chavarin, Carlos and Schubert, Markus Andreas and Wenger, Christian and Henkel, Karsten and Flege, Jan Ingo},
title = {Combination of Multiple Operando and In-Situ Characterization Techniques in a Single Cluster System for Atomic Layer Deposition: Unraveling the Early Stages of Growth of Ultrathin Al2O3 Films on Metallic Ti Substrates},
series = {Inorganics},
volume = {11},
journal = {Inorganics},
number = {12},
issn = {2304-6740},
doi = {10.3390/inorganics11120477},
abstract = {This work presents a new ultra-high vacuum cluster tool to perform systematic studies of the early growth stages of atomic layer deposited (ALD) ultrathin films following a surface science approach. By combining operando (spectroscopic ellipsometry and quadrupole mass spectrometry) and in situ (X-ray photoelectron spectroscopy) characterization techniques, the cluster allows us to follow the evolution of substrate, film, and reaction intermediates as a function of the total number of ALD cycles, as well as perform a constant diagnosis and evaluation of the ALD process, detecting possible malfunctions that could affect the growth, reproducibility, and conclusions derived from data analysis. The homemade ALD reactor allows the use of multiple precursors and oxidants and its operation under pump and flow-type modes. To illustrate our experimental approach, we revisit the well-known thermal ALD growth of Al2O3 using trimethylaluminum and water. We deeply discuss the role of the metallic Ti thin film substrate at room temperature and 200 °C, highlighting the differences between the heterodeposition (<10 cycles) and the homodeposition (>10 cycles) growth regimes at both conditions. This surface science approach will benefit our understanding of the ALD process, paving the way toward more efficient and controllable manufacturing processes.},
language = {en}
}
@misc{FranckDabrowskiSchubertetal.,
author = {Franck, Max and Dabrowski, Jarek and Schubert, Markus Andreas and Vignaud, Dominique and Achehboune, Mohamed and Colomer, Jean-Fran{\c{c}}ois and Henrard, Luc and Wenger, Christian and Lukosius, Mindaugas},
title = {Investigating Impacts of Local Pressure and Temperature on CVD Growth of Hexagonal Boron Nitride on Ge(001)/Si},
series = {Advanced Materials Interfaces},
volume = {12},
journal = {Advanced Materials Interfaces},
number = {1},
publisher = {Wiley},
issn = {2196-7350},
doi = {10.1002/admi.202400467},
pages = {9},
abstract = {AbstractThe chemical vapor deposition (CVD) growth of hexagonal boron nitride (hBN) on Ge substrates is a promising pathway to high-quality hBN thin films without metal contaminations for microelectronic applications, but the effect of CVD process parameters on the hBN properties is not well understood yet. The influence of local changes in pressure and temperature due to different reactor configurations on the structure and quality of hBN films grown on Ge(001)/Si is studied. Injection of the borazine precursor close to the sample surface results in an inhomogeneous film thickness, attributed to an inhomogeneous pressure distribution at the surface, as shown by computational fluid dynamics simulations. The additional formation of nanocrystalline islands is attributed to unfavorable gas phase reactions due to the radiative heating of the injector. Both issues are mitigated by increasing the injector-sample distance, leading to an 86\% reduction in pressure variability on the sample surface and a 200 °C reduction in precursor temperature. The resulting hBN films exhibit no nanocrystalline islands, improved thickness homogeneity, and high crystalline quality (Raman FWHM = 23 cm-1). This is competitive with hBN films grown on other non-metal substrates but achieved at lower temperature and with a low thickness of only a few nanometers.},
language = {en}
}
@misc{MoralesGertigKotetal.,
author = {Morales, Carlos and Gertig, Max and Kot, Małgorzata and Alvarado, Carlos and Schubert, Markus Andreas and Zoellner, Marvin Hartwig and Wenger, Christian and Henkel, Karsten and Flege, Jan Ingo},
title = {In situ X-ray photoelectron spectroscopy study of atomic layer deposited cerium oxide on SiO₂ : substrate influence on the reaction mechanism during the early stages of growth},
series = {Advanced materials interfaces},
volume = {12},
journal = {Advanced materials interfaces},
number = {5},
publisher = {Wiley},
address = {Weinheim},
issn = {2196-7350},
doi = {10.1002/admi.202400537},
pages = {1 -- 13},
abstract = {Thermal atomic layer deposition (ALD) of cerium oxide using commercial Ce(thd)4 precursor and O3 on SiO2 substrates is studied employing in-situ X-ray photoelectron spectroscopy (XPS). The system presents a complex growth behavior determined by the change in the reaction mechanism when the precursor interacts with the substrate or the cerium oxide surface. During the first growth stage, non-ALD side reactions promoted by the substrate affect the growth per cycle, the amount of carbon residue on the surface, and the oxidation degree of cerium oxide. On the contrary, the second growth stage is characterized by a constant growth per cycle in good agreement with the literature, low carbon residues, and almost fully oxidized cerium oxide films. This distinction between two growth regimes is not unique to the CeOx/SiO2 system but can be generalized to other metal oxide substrates. Furthermore, the film growth deviates from the ideal layer-by-layer mode, forming micrometric inhomogeneous and defective flakes that eventually coalesce for deposit thicknesses above 10 nm. The ALD-cerium oxide films present less order and a higher density of defects than films grown by physical vapor deposition techniques, likely affecting their reactivity in oxidizing and reducing conditions.},
language = {en}
}