@misc{StrobelAlvaradoChavarinLeszczynskietal., author = {Strobel, Carsten and Alvarado Chavarin, Carlos and Leszczynski, Sebastian and Richter, Karola and Knaut, Martin and Reif, Johanna and V{\"o}lkel, Sandra and Albert, Matthias and Wenger, Christian and Bartha, Johann Wolfgang and Mikolajick, Thomas}, title = {Improved Graphene-base Heterojunction Transistor with Different Collector Semi-conductors for High-frequency Applications}, series = {Advanced Materials Letters}, volume = {13}, journal = {Advanced Materials Letters}, number = {1}, issn = {0976-3961}, doi = {10.5185/amlett.2022.011688}, abstract = {A new kind of transistor device with a graphene monolayer embedded between two n-type silicon layers is fabricated and characterized. The device is called graphene-base heterojunction transistor (GBHT). The base-voltage controls the current of the device flowing from the emitter via graphene to the collector. The transit time for electrons passing by the ultrathin graphene layer is extremely short which makes the device very promising for high frequency RF-electronics. The output current of the device is saturated and clearly modulated by the base voltage. Further, the silicon collector of the GBHT is replaced by germanium to improve the device performance. This enabled the collector current to be increased by almost three orders of magnitude. Also, the common-emitter current gain (Ic/Ib) increased from 10-3 to approximately 0.3 for the newly designed device. However, the ON-OFF ratio of the improved germanium based GBHT has so far been rather low. Further optimizations are necessary in order to fully exploit the potential of the graphene-base heterojunction transistor.}, language = {en} } @misc{StrobelAlvaradoChavarinRichteretal., author = {Strobel, Carsten and Alvarado Chavarin, Carlos and Richter, Karola and Knaut, Martin and Reif, Johanna and Völkel, Sandra and Jahn, Andreas and Albert, Matthias and Wenger, Christian and Kirchner, Robert and Bartha, Johann Wolfgang and Mikolajick, Thomas}, title = {Novel Graphene Adjustable-Barrier Transistor with Ultra-High Current Gain}, series = {ACS Applied Materials \& Interfaces}, volume = {14}, journal = {ACS Applied Materials \& Interfaces}, number = {34}, issn = {1944-8244}, doi = {10.1021/acsami.2c10634}, pages = {39249 -- 39254}, abstract = {A graphene-based three terminal barristor device was proposed to overcome the low on/off ratios and insufficient current saturation of conventional graphene field effect transistors. In this study, we fabricated and analyzed a novel graphene-based transistor, which resembles the structure of the barristor but uses a different operating condition. This new device, termed graphene adjustable-barriers transistor (GABT), utilizes a semiconductor-based gate rather than a metal-insulator gate structure to modulate the device currents. The key feature of the device is the two graphene-semiconductor Schottky barriers with different heights that are controlled simultaneously by the gate voltage. Due to the asymmetry of the barriers, the drain current exceeds the gate current by several orders of magnitude. Thus, the GABT can be considered an amplifier with an alterable current gain. In this work, a silicon-graphene-germanium GABT with an ultra-high current gain (ID/IG up to 8 × 106) was fabricated, and the device functionality was demonstrated. Additionally, a capacitance model is applied to predict the theoretical device performance resulting in an on-off ratio above 106, a swing of 87 mV/dec, and a drivecurrent of about 1 × 106 A/cm2.}, language = {en} } @misc{NgũgĩRichterBraunUnkhoffetal., author = {Ngũgĩ, John Mbũrũ and Richter, Sandra and Braun-Unkhoff, Marina and Naumann, Clemens and Riedel, Uwe}, title = {A study on fundamental combustion properties of trimethyl orthoformate: experiments and modeling}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {145}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {2}, publisher = {ASME International}, issn = {0742-4795}, doi = {10.1115/1.4055828}, abstract = {Trimethyl orthoformate (TMOF: HC(OCH3)3) has recently been examined as a viable biofuel. TMOF is a branched isomer of oxymethylene ether-2 (OME2) that, due to its high oxygen content and lack of direct carbon-carbon bonds, considerably reduces the formation of soot particles. To meet the challenges of a more flexible and sustainable power generation, a detailed understanding of its combustion properties is essential for its safe and efficient utilization, neat or in blends. In this work, two fundamental combustion properties of TMOF were studied: (i) Auto-ignition of TMOF/synthetic air mixtures (φ = 1.0; diluted 1:5 with N2) using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) Laminar burning velocities of TMOF/air mixtures using the cone angle method at ambient and elevated pressures of 3 and 6 bar. Furthermore, the impact of TMOF addition to a gasoline surrogate (PRF90) on ignition delay times was studied using the shock tube method at φ = 1.0, 1:5 dilution with N2, T = 900-2000}, language = {en} } @misc{RichterKukkadapuWestbrooketal., author = {Richter, Sandra and Kukkadapu, Goutham and Westbrook, Charles K. and Braun-Unkhoff, Marina and Naumann, Clemens and K{\"o}hler, Markus and Riedel, Uwe}, title = {A combined experimental and modeling study of combustion properties of an isoparaffinic alcohol-to-jet fuel}, series = {Combustion and Flame}, volume = {240}, journal = {Combustion and Flame}, publisher = {Elsevier BV}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2022.111994}, pages = {15}, language = {en} } @misc{NgũgĩRichterBraunUnkhoffetal., author = {Ngũgĩ, John Mbũrũ and Richter, Sandra and Braun-Unkhoff, Marina and Naumann, Clemens and Riedel, Uwe}, title = {A study on fundamental combustion properties of oxymethylene ether-1, the primary reference fuel 90, and their blend: experiments and modeling}, series = {Combustion and Flame}, volume = {243}, journal = {Combustion and Flame}, publisher = {Elsevier BV}, issn = {0010-2180}, doi = {10.1016/j.combustflame.2022.111996}, pages = {14}, language = {en} } @misc{NgũgĩRichterBraunUnkhoffetal., author = {Ngũgĩ, John Mbũrũ and Richter, Sandra and Braun-Unkhoff, Marina and Naumann, Clemens and Riedel, Uwe}, title = {A study on fundamental combustion properties of trimethyl orthoformate: experiments and modeling}, series = {Volume 2: Coal, Biomass, Hydrogen, and Alternative Fuels; Controls, Diagnostics, and Instrumentation; Steam Turbine}, journal = {Volume 2: Coal, Biomass, Hydrogen, and Alternative Fuels; Controls, Diagnostics, and Instrumentation; Steam Turbine}, publisher = {American Society of Mechanical Engineers}, isbn = {978-0-7918-8598-7}, doi = {10.1115/GT2022-83029}, abstract = {Trimethyl orthoformate (TMOF: HC(OCH3)3) has recently been examined as a viable biofuel. TMOF is a branched isomer of oxymethylene ether-2 (OME2) that, due to its high oxygen content and lack of direct carbon-carbon bonds, considerably reduces the formation of soot particles. To meet the challenges of a more flexible and sustainable power generation, a detailed understanding of its combustion properties is essential for its safe and efficient utilization, neat or in blends. In this work, two fundamental combustion properties of TMOF were studied: (i) Auto-ignition of TMOF / synthetic air mixtures (φ = 1.0; diluted 1:5 with N2) using the shock tube method at pressures of 1, 4, and 16 bar, and (ii) Laminar burning velocities of TMOF / air mixtures using the cone angle method at ambient and elevated pressures of 3 and 6 bar. Furthermore, the impact of TMOF addition to a gasoline surrogate (PRF90) on ignition delay times was studied using the shock tube method at φ = 1.0, 1:5 dilution with N2, T = 900-2}, language = {en} }