@article{doi:10.1021/acsphotonics.0c00361,

title = {Highly Responsive Flexible Photodetectors Based on MOVPE Grown Uniform Few-Layer MoS2},

author = {Daniel S Schneider and Annika Grundmann and Andreas Bablich and Vikram Passi and Satender Kataria and Holger Kalisch and Michael Heuken and Andrei Vescan and Daniel Neumaier and Max C Lemme},

url = {https://doi.org/10.1021/acsphotonics.0c00361},

doi = {10.1021/acsphotonics.0c00361},

year  = {2020},

date = {2020-01-01},

journal = {ACS Photonics},

volume = {7},

number = {6},

pages = {1388-1395},

abstract = {Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are seen as promising candidates for flexible electronic and optoelectronic devices due to their high tensile strength and favorable optical properties. Molybdenum disulfide (MoS2) is a benchmark material for TMDCs, which has already been studied extensively. Here, we report on highly responsive flexible few-layer MoS2 photodetectors based on MoS2 synthesized uniformly for full coverage of 2 in. sapphire wafers using metalorganic vapor-phase epitaxy (MOVPE). Device performance is studied by electro-optical characterization. Electrostatic gating allows tuning both the responsivity between 150 and 920 A/W and the specific detectivity between almost 1012 and 1010 Jones. The measured spectrally resolved responsivities of the detectors suggest applications in the blue-light range, with opportunities for fine-tuning the most sensitive wavelength through gating, as shown through optical simulations. Finally, the flexible devices were bent to demonstrate their suitability for flexible electronics in fields of future Internet of Things and medical devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Illarionov2020,

title = {Insulators for 2D nanoelectronics: the gap to bridge},

author = {Yury Yu. Illarionov and Theresia Knobloch and Markus Jech and Mario Lanza and Deji Akinwande and Mikhail I Vexler and Thomas Mueller and Max C Lemme and Gianluca Fiori and Frank Schwierz and Tibor Grasser},

url = {https://doi.org/10.1038/s41467-020-16640-8},

issn = {2041-1723},

year  = {2020},

date = {2020-01-01},

journal = {Nature Communications},

volume = {11},

number = {1},

pages = {3385},

abstract = {Nanoelectronic devices based on 2D materials are far from delivering their full theoretical performance potential due to the lack of scalable insulators. Amorphous oxides that work well in silicon technology have ill-defined interfaces with 2D materials and numerous defects, while 2D hexagonal boron nitride does not meet required dielectric specifications. The list of suitable alternative insulators is currently very limited. Thus, a radically different mindset with respect to suitable insulators for 2D technologies may be required. We review possible solution scenarios like the creation of clean interfaces, production of native oxides from 2D semiconductors and more intensive studies on crystalline insulators.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/5.0022975,

title = {Ultrahigh-performance integrated inverters based on amorphous zinc tin oxide deposited at room temperature},

author = {Oliver Lahr and Holger von Wenckstern and Marius Grundmann},

url = {https://doi.org/10.1063/5.0022975},

doi = {10.1063/5.0022975},

year  = {2020},

date = {2020-01-01},

journal = {APL Materials},

volume = {8},

number = {9},

pages = {091111},

abstract = {Recent advances in the field of integrated circuits based on sustainable and transparent amorphous oxide semiconductors (AOSs) are presented, demonstrating ultrahigh performance operating state-of-the-art integrated inverters comprising metal\textendashsemiconductor field-effect transistors (MESFETs) with amorphous zinc tin oxide (ZTO) as a channel material. All individual circuit layers have been deposited entirely at room temperature, and the completed devices did not require undergoing additional thermal annealing treatment in order to facilitate proper device functionality. The demonstrated ZTO-based MESFETs exhibit current on/off ratios of over 8 orders of magnitude a field-effect mobility of 8.4 cm2 V−1 s−1, and they can be switched within a voltage range of less than 1.5 V attributed to their small subthreshold swing as low as 86 mV decade−1. Due to adjustments of the circuit layout and, thus, the improvement of certain geometry-related transistor properties, the associated Schottky diode FET logic inverters facilitate low-voltage switching by exhibiting a remarkable maximum voltage gain of up to 1190 with transition voltages of only 80 mV while operating at low supply voltages ≤3 V and maintaining a stable device performance under level shift. To the best of our knowledge, the presented integrated inverters clearly exceed the performance of any similar previously reported devices based on AOS, and thus, prove the enormous potential of amorphous ZTO for sustainable, scalable low-power electronics within future flexible and transparent applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.5143217,

title = {Low voltage, high gain inverters based on amorphous zinc tin oxide on flexible substrates},

author = {P Schlupp and S Vogt and H von Wenckstern and M Grundmann},

url = {https://doi.org/10.1063/1.5143217},

doi = {10.1063/1.5143217},

year  = {2020},

date = {2020-01-01},

journal = {APL Materials},

volume = {8},

number = {6},

pages = {061112},

abstract = {Deposition of semiconductors on bendable substrates is a crucial step toward flexible circuitry and deposition by a roll-to-roll process. Since most bendable substrates have limited temperature stability (normally degradation starts between 150 °C and 300 °C), processing temperatures are typically below that of rigid substrates. Amorphous oxide semiconductors (AOSs) such as indium gallium zinc oxide (IGZO) can be fabricated at room temperature (RT) and exhibit electron mobilities >10 cm2 V−1 s−1 being a pre-requisite for application in backplanes of displays. While IGZO is already commercially exploited, the search for alternative materials is highly relevant because indium and gallium are rare and expensive. Zinc tin oxide (ZTO) is a promising AOS since zinc and tin are highly abundant and cheap. In this letter, we discuss RT-fabricated n-type ZTO thin films used as the channel material in flexible inverter circuits based on junction field-effect transistors. RT-fabricated nickel oxide is used as a semitransparent p-type gate material. The devices are fabricated on flexible polyimide and exhibit an excellent peak gain magnitude of 464 and uncertainty level as low as 130 mV at a supply voltage of only 3 V. They are characterized before and after bending at various radii. Even after bending at 2 mm radius, the inverters behave still very well.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/aelm.202000423,

title = {All-Oxide Transparent Thin-Film Transistors Based on Amorphous Zinc Tin Oxide Fabricated at Room Temperature: Approaching the Thermodynamic Limit of the Subthreshold Swing},

author = {Oliver Lahr and Michael S Bar and Holger von Wenckstern and Marius Grundmann},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aelm.202000423},

doi = {https://doi.org/10.1002/aelm.202000423},

year  = {2020},

date = {2020-01-01},

journal = {Advanced Electronic Materials},

volume = {6},

number = {10},

pages = {2000423},

abstract = {Abstract Thin-film transistors (TFTs) based on transparent amorphous oxide semiconductors (TAOSs) have become essential building blocks for a broad range of electronics, since TAOSs facilitate large-scale fabrication at moderate temperatures and hence feature compatibility with flexible substrates. An emerging indium-free alternative to the widely commercially exploited indium gallium zinc oxide (IGZO) is amorphous zinc tin oxide (ZTO); however, according to previous reports, achieving acceptable performance of ZTO-based devices fabricated at temperatures below 300 °C is still challenging to date. Here, key properties of the first all-oxide and fully transparent metal-semiconductor field-effect transistors (MESFETs), metal-insulator-semiconductor field-effect transistors (MISFETs) and junction field-effect transistors (JFETs) based on amorphous ZTO are compared, employing PtOx, HfOy, and p-type NiO as gate, respectively. All individual layers have been deposited exclusively at room temperature and do not require any additional postdeposition annealing to obtain sufficient device functionality. Demonstrated TFTs exhibit reasonable current on/off ratios of over six orders of magnitude with subthreshold swings as low as 61 mV dec\textendash1 at room temperature. Transistor characteristics have been recorded for several weeks to study performance consistency over time and are further investigated regarding their stability under bias stress.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/aelm.201901066,

title = {Metal\textendashSemiconductor Field-Effect Transistors Based on the Amorphous Multi-Anion Compound ZnON},

author = {Anna Reinhardt and Holger von Wenckstern and Marius Grundmann},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aelm.201901066},

doi = {https://doi.org/10.1002/aelm.201901066},

year  = {2020},

date = {2020-01-01},

journal = {Advanced Electronic Materials},

volume = {6},

number = {4},

pages = {1901066},

abstract = {Abstract Electrical properties of metal\textendashsemiconductor field-effect transistors (MESFETs) based on the amorphous n-type multi-anion compound zinc oxynitride (ZnON) comprising reactively sputtered platinum as Schottky gate are presented. The Schottky barrier diodes reveal a rectification ratio of 4 × 103 at ±2 V and an ideality factor of 1.43. The investigated MESFETs show good switching characteristics with a switching voltage below 2 V, low subthreshold swing of 112 mV dec−1 and reasonable current on/off ratios up to 5 × 105. Additionally, the stability of the devices under visible light illumination is proven.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/admi.201902145,

title = {Effect of the Degree of the Gate-Dielectric Surface Roughness on the Performance of Bottom-Gate Organic Thin-Film Transistors},

author = {Michael Geiger and Rachana Acharya and Eric Reutter and Thomas Ferschke and Ute Zschieschang and J\"{u}rgen Weis and Jens Pflaum and Hagen Klauk and Ralf Thomas Weitz},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/admi.201902145},

doi = {https://doi.org/10.1002/admi.201902145},

year  = {2020},

date = {2020-01-01},

journal = {Advanced Materials Interfaces},

volume = {7},

number = {10},

pages = {1902145},

abstract = {Abstract In organic thin-film transistors (TFTs) fabricated in the inverted (bottom-gate) device structure, the surface roughness of the gate dielectric onto which the organic-semiconductor layer is deposited is expected to have a significant effect on the TFT characteristics. To quantitatively evaluate this effect, a method to tune the surface roughness of a gate dielectric consisting of a thin layer of aluminum oxide and an alkylphosphonic acid self-assembled monolayer over a wide range by controlling a single process parameter, namely the substrate temperature during the deposition of the aluminum gate electrodes, is developed. All other process parameters remain constant in the experiments, so that any differences observed in the TFT performance can be confidently ascribed to effects related to the difference in the gate-dielectric surface roughness. It is found that an increase in surface roughness leads to a significant decrease in the effective charge-carrier mobility and an increase in the subthreshold swing. It is shown that a larger gate-dielectric surface roughness leads to a larger density of grain boundaries in the semiconductor layer, which in turn produces a larger density of localized trap states in the semiconductor.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Borcherteaaz5156,

title = {Flexible low-voltage high-frequency organic thin-film transistors},

author = {James W Borchert and Ute Zschieschang and Florian Letzkus and Michele Giorgio and Thomas R Weitz and Mario Caironi and Joachim N Burghartz and Sabine Ludwigs and Hagen Klauk},

url = {https://advances.sciencemag.org/content/6/21/eaaz5156},

doi = {10.1126/sciadv.aaz5156},

year  = {2020},

date = {2020-01-01},

journal = {Science Advances},

volume = {6},

number = {21},

publisher = {American Association for the Advancement of Science},

abstract = {The primary driver for the development of organic thin-film transistors (TFTs) over the past few decades has been the prospect of electronics applications on unconventional substrates requiring low-temperature processing. A key requirement for many such applications is high-frequency switching or amplification at the low operating voltages provided by lithium-ion batteries (~3 V). To date, however, most organic-TFT technologies show limited dynamic performance unless high operating voltages are applied to mitigate high contact resistances and large parasitic capacitances. Here, we present flexible low-voltage organic TFTs with record static and dynamic performance, including contact resistance as small as 10 Ωtextperiodcenteredcm, on/off current ratios as large as 1010, subthreshold swing as small as 59 mV/decade, signal delays below 80 ns in inverters and ring oscillators, and transit frequencies as high as 21 MHz, all while using an inverted coplanar TFT structure that can be readily adapted to industry-standard lithographic techniques.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/adfm.201903812,

title = {Roadmap to Gigahertz Organic Transistors},

author = {Ute Zschieschang and James W Borchert and Michele Giorgio and Mario Caironi and Florian Letzkus and Joachim N Burghartz and Ulrike Waizmann and J\"{u}rgen Weis and Sabine Ludwigs and Hagen Klauk},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201903812},

doi = {https://doi.org/10.1002/adfm.201903812},

year  = {2020},

date = {2020-01-01},

journal = {Advanced Functional Materials},

volume = {30},

number = {20},

pages = {1903812},

abstract = {Abstract Despite the large body of research conducted on organic transistors, the transit frequency of organic field-effect transistors has seen virtually no improvement for a decade and remains far below 1 GHz. One reason is that most of the research is still focused on improving the charge-carrier mobility, a parameter that has little influence on the transit frequency of short-channel transistors. By examining the fundamental equations for the transit frequency of field-effect transistors and by extrapolating recent progress on the relevant device parameters, a roadmap to gigahertz organic transistors is derived.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{9024051,

title = {Charge-Based Compact Modeling of Capacitances in Staggered Multi-Finger OTFTs},

author = {J Leise and J Pruefer and G Darbandy and M Seifaei and Y Manoli and H Klauk and U Zschieschang and B I\~{n}iguez and A Kloes},

doi = {10.1109/JEDS.2020.2978400},

issn = {2168-6734},

year  = {2020},

date = {2020-01-01},

journal = {IEEE Journal of the Electron Devices Society},

volume = {8},

pages = {396-406},

abstract = {This journal paper introduces a charge-based approach for the calculation of charges and capacitances in staggered organic thin-film transistors (OTFTs). Based on an already existing DC model, the charges are yielded in an analytical and compact form. A linear charge partitioning scheme is applied to ascribe charges to the drain/source side of the channel. The final equation is only dependent on geometrical parameters and the charge densities at the drain/source end of the channel. Furthermore, the fringing regions in fabricated devices are taken into account. The compact model is implemented in Verilog-A and the capacitances are compared to Sentaurus TCAD simulation results as well as measurement data. Additionally, simulation results for a differential amplifier are compared to measurements. The advantage of this model is its unique formulation covering all operation regimes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Darwish_2019,

title = {A drift-diffusion simulation model for organic field effect transistors: on the importance of the Gaussian density of states and traps},

author = {Mohammed Darwish and Alessio Gagliardi},

url = {https://doi.org/10.1088/1361-6463/ab605d},

doi = {10.1088/1361-6463/ab605d},

year  = {2019},

date = {2019-12-01},

journal = {Journal of Physics D: Applied Physics},

volume = {53},

number = {10},

pages = {105102},

publisher = {IOP Publishing},

abstract = {The nature of charge transport in organic materials depends on several important aspects, such as the description of the density of states, and the charge mobility model. Therefore specific models describing electronic properties of organic semiconductors must be considered. We have used an organic based drift-diffusion model for the electrical characterization of organic field effect transistors (OFETs) utilizing either small molecules or polymers. Furthermore, the effect of interface traps, bulk traps, and fixed charges on transistor characteristics are included and investigated. Finally, simulation results are compared to experimental measurements, and conclusions are drawn out in terms of transistor performance parameters including threshold voltages, and field-dependent mobilities.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8854319,

title = {Compact DC Modeling of Organic Thin-Film Transistors Including Their Parasitic Non-Linear Contact Effects Based on a Novel Extraction Method},

author = {S Elsaegh and U Zschieschang and J W Borchert and H Klauk and H Zappe and Y Manoli},

doi = {10.1109/TED.2019.2941438},

issn = {1557-9646},

year  = {2019},

date = {2019-11-01},

journal = {IEEE Transactions on Electron Devices},

volume = {66},

number = {11},

pages = {4907-4914},

abstract = {This article presents a novel generic method for the extraction of the current-voltage characteristics of organic thin-film transistors (TFTs) that specifically accounts for the individual contributions of the source and drain contacts and their nonlinear behavior. Based on this extraction method, an analytical model has been derived that describes the behavior of the intrinsic TFT and of the source and drain contacts both in the linear and the saturation regimes. The essential feature of the proposed extraction method is that it does not depend on or assume any physical phenomena underlying the electrical characteristics of the contacts. Instead, it extracts the current-voltage characteristics of the contacts which can then be fit to any physics-based TFT model. This is beneficial both for circuit designers and for those developing physics-based TFT models. The proposed extraction method has been applied to organic TFTs fabricated on flexible plastic substrates in the staggered and coplanar device architectures using two different small-molecule organic semiconductors. The compact dc model has been used to simulate organic TFTs with channel lengths ranging from 4 to 100 μm and a transimpedance amplifier circuit based on TFTs with different channel lengths, and the results are in good agreement with the measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8854293,

title = {Modified Bootstrap Switching Scheme for Organic Digital Integrated Circuits},

author = {M Seifaei and D Schillinger and M Kuhl and M Keller and U Zschieschang and H Klauk and Y Manoli},

doi = {10.1109/LSSC.2019.2944854},

issn = {2573-9603},

year  = {2019},

date = {2019-10-01},

journal = {IEEE Solid-State Circuits Letters},

volume = {2},

number = {10},

pages = {219-222},

abstract = {The design and implementation of a modified bootstrap switching circuit based on p-channel organic thin-film transistors and integrated thin-film resistors that addresses the lack of high-performance n-channel organic transistors is presented. Using the bootstrap technique, the fall time of the output stage is decreased by more than a factor of 10, resulting in a 10.39 times higher operating frequency for a load capacitance of 10 nF, and rail-to-rail output swing is achieved. A minimum-area inverter and a Schmitt-trigger-based inverter are presented that serve as references for comparison and as small-footprint alternatives to the bootstrap circuit. The dynamic performance of the proposed circuits is validated by comparing three different ring oscillator implementations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8721229,

title = {5\textendash31-Hz 188-µW Light-Sensing Oscillator With Two Active Inductors Fully Integrated on Plastic},

author = {T Meister and K Ishida and S Knobelspies and G Cantarella and N M\"{u}nzenrieder and G Tr\"{o}ster and C Carta and F Ellinger},

doi = {10.1109/JSSC.2019.2914405},

issn = {0018-9200},

year  = {2019},

date = {2019-08-01},

journal = {IEEE Journal of Solid-State Circuits},

volume = {54},

number = {8},

pages = {2195-2206},

abstract = {We present a low-power low-frequency oscillator that is fully integrated on a bendable plastic substrate using amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). Its purpose is the duty cycling of components of a wireless sensor tag to realize power savings. In addition, the oscillator can directly be used as a light sensor. It oscillates between 5 Hz in the dark and 31 Hz under daylight, from a 5-V supply voltage. The measured light-sensitivity of the oscillation frequency is between 7.4 Hz/klx in the dark and around 1.7 Hz/klx in daylight. On average, the frequency of oscillation changes by 58 %/klx. The required power is 188 $mu textW$ . The presented design is a combination of the inductance\textendashcapacitance cross-coupled oscillator structure and two single-transistor active inductors, which enable high gain at low power levels in a small chip area. We analyze the circuit and derive design guidelines for minimizing the oscillation frequency, circuit area, and power consumption. Finally, we report the measurements including jitter and deduce implications for the accuracy of light measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8750804,

title = {Full-Swing, High-Gain Inverters Based on ZnSnO JFETs and MESFETs},

author = {O Lahr and Z Zhang and F Grotjahn and P Schlupp and S Vogt and H von Wenckstern and A Thiede and M Grundmann},

doi = {10.1109/TED.2019.2922696},

issn = {0018-9383},

year  = {2019},

date = {2019-08-01},

journal = {IEEE Transactions on Electron Devices},

volume = {66},

number = {8},

pages = {3376-3381},

abstract = {Metal\textendashsemiconductor and junction n-channel field-effect transistors (MESFETs and JFETs) have been fabricated on glass substrates using room temperature deposited amorphous zinc\textendashtin oxide (ZTO) channel layers. Characteristics of transistors and inverter circuits are compared. Best FET devices exhibit ON-to- OFF current ratios over eight orders of magnitude, subthreshold swings as low as 250 mV/dec and field-effect mobilities of 5 cm2/Vs. Furthermore, all devices show long-term stability over a period of more than 200 days. Inverters fabricated using either MESFETs or JFETs exhibit remarkable peak gain magnitude values of 350 and voltage uncertainty levels as low as 260 mV for an operating voltage of 5 V. A Schottky diode FET logic (SDFL) approach is applied to shift the switching voltage which is a requirement for cascading of inverters for realization of ring oscillators.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Strobel2019.DOISTART,

title = {Prototype of a novel graphene base heterojunction transistor},

author = {C Strobel and C A Chavarin and B Leszczynska and S Leszczynski and F Winkler and S Killge and S V\"{o}lkel and K Richter and A Hiess and M Knaut and J Reif and M Albert and Ch. Wenger and J W Bartha},

year  = {2019},

date = {2019-06-01},

journal = {9th edition of Graphene Conference series, Rome},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8586929,

title = {Evaluation of the Beyond- fT Operation of an IGZO TFT-Based RF Self-Mixing Circuit},

author = {U Kalita and C Tueckmantel and T Riedl and U Pfeiffer},

doi = {10.1109/LMWC.2018.2886068},

issn = {1531-1309},

year  = {2019},

date = {2019-02-01},

journal = {IEEE Microwave and Wireless Components Letters},

volume = {29},

number = {2},

pages = {119-121},

abstract = {The objective of this letter is to show the potential of amorphous indium gallium zinc oxide (IGZO) thin-film transistors (TFT) for designing radio frequency (RF) communication systems operating in the gigahertz regime. For that purpose, the self-mixing operation of in-house fabricated IGZO-TFTs beyond their transit frequency (fT) is reported. The bottom-gate, top-contact TFTs have an fT of 40 MHz including the device interconnects. A differential RF self-mixing circuit was fabricated to act as an RF detector and frequency doubler. The detector shows a peak voltage responsivity (RV) and a minimum noise equivalent power of 445 V/W and 0.1 nW/√(Hz) at 50 MHz and 2 V/W and 30 nW/√(Hz) at 1 GHz, respectively, at a chopping frequency of 28 kHz. As a frequency doubler, the circuit can generate a second-harmonic output voltage up to -36 dBV for an 8-dBV RF input voltage at 100 MHz.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Borchert2019.DOISTART,

title = {Small contact resistance and high-frequency operation of flexible low-voltage inverted coplanar organic transistors},

author = {James W Borchert and Boyu Peng and Florian Letzkus and Joachim N Burghartz and Paddy K L Chan and Karin Zojer and Sabine Ludwigs and Hagen Klauk},

url = {https://doi.org/10.1038/s41467-019-09119-8},

issn = {2041-1723},

year  = {2019},

date = {2019-01-01},

journal = {Nature Communications},

volume = {10},

number = {1},

pages = {1119},

abstract = {The contact resistance in organic thin-film transistors (TFTs) is the limiting factor in the development of high-frequency organic TFTs. In devices fabricated in the inverted (bottom-gate) device architecture, staggered (top-contact) organic TFTs have usually shown or are predicted to show lower contact resistance than coplanar (bottom-contact) organic TFTs. However, through comparison of organic TFTs with different gate-dielectric thicknesses based on the small-molecule organic semiconductor 2,9-diphenyl-dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene, we show the potential for bottom-contact TFTs to have lower contact resistance than top-contact TFTs, provided the gate dielectric is sufficiently thin and an interface layer such as pentafluorobenzenethiol is used to treat the surface of the source and drain contacts. We demonstrate bottom-contact TFTs fabricated on flexible plastic substrates with record-low contact resistance (29 Ωcm), record subthreshold swing (62 mV/decade), and signal-propagation delays in 11-stage unipolar ring oscillators as short as 138 ns per stage, all at operating voltages of about 3 V.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Acharya2019.acsami.9b04361,

title = {Achieving Ultralow Turn-On Voltages in Organic Thin-Film Transistors: Investigating Fluoroalkylphosphonic Acid Self-Assembled Monolayer Hybrid Dielectrics},

author = {Rachana Acharya and Boyu Peng and Paddy K L Chan and Guido Schmitz and Hagen Klauk},

url = {https://doi.org/10.1021/acsami.9b04361},

doi = {10.1021/acsami.9b04361},

issn = {1944-8244},

year  = {2019},

date = {2019-01-01},

journal = {ACS Appl. Mater. Interfaces},

volume = {11},

number = {30},

pages = {27104--27111},

publisher = {American Chemical Society},

abstract = {The properties of organic thin-film transistors (TFTs) and thus their ability to address specific circuit design requirements depend greatly on the choice of the materials, particularly the organic semiconductor and the gate dielectric. For a particular organic semiconductor, the TFT performance must be reviewed for different combinations of substrates, fabrication conditions, and the choice of the gate dielectric in order to achieve the optimum TFT and circuit characteristics. We have fabricated and characterized organic TFTs based on the small-molecule organic semiconductor 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene in combination with an ultrathin hybrid gate dielectric consisting of aluminum oxide and a self-assembled monolayer. Fluoroalkylphosphonic acids with chain lengths ranging from 6 to 14 carbon atoms have been used to form the self-assembled monolayer in the gate dielectric, and their influence on the TFT characteristics has been studied. By optimizing the fabrication conditions, a turn-on voltage of 0 V with an on/off current ratio above 106 has been achieved, in combination with charge-carrier mobilities up to 0.4 cm2/V s on flexible plastic substrates and 1 cm2/V s on silicon substrates. 

The properties of organic thin-film transistors (TFTs) and thus their ability to address specific circuit design requirements depend greatly on the choice of the materials, particularly the organic semiconductor and the gate dielectric. For a particular organic semiconductor, the TFT performance must be reviewed for different combinations of substrates, fabrication conditions, and the choice of the gate dielectric in order to achieve the optimum TFT and circuit characteristics. We have fabricated and characterized organic TFTs based on the small-molecule organic semiconductor 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene in combination with an ultrathin hybrid gate dielectric consisting of aluminum oxide and a self-assembled monolayer. Fluoroalkylphosphonic acids with chain lengths ranging from 6 to 14 carbon atoms have been used to form the self-assembled monolayer in the gate dielectric, and their influence on the TFT characteristics has been studied. By optimizing the fabrication conditions, a turn-on voltage of 0 V with an on/off current ratio above 106 has been achieved, in combination with charge-carrier mobilities up to 0.4 cm2/V s on flexible plastic substrates and 1 cm2/V s on silicon substrates.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1063/1.5093167,

title = {Demonstration of a graphene-base heterojunction transistor with saturated output current},

author = {C Strobel and C A Chavarin and B Leszczynska and S Leszczynski and F Winkler and S Killge and S V\"{o}lkel and K Richter and A Hiess and M Knaut and J Reif and M Albert and Ch. Wenger and J W Bartha},

url = {https://doi.org/10.1063/1.5093167},

doi = {10.1063/1.5093167},

year  = {2019},

date = {2019-01-01},

journal = {Journal of Applied Physics},

volume = {125},

number = {23},

pages = {234501},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/aelm.201900576,

title = {Electrically Stable Organic Permeable Base Transistors for Display Applications},

author = {Felix Dollinger and Henning Iseke and Erjuan Guo and Axel Fischer and Hans Kleemann and Karl Leo},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aelm.201900576},

doi = {https://doi.org/10.1002/aelm.201900576},

year  = {2019},

date = {2019-01-01},

journal = {Advanced Electronic Materials},

volume = {5},

number = {12},

pages = {1900576},

abstract = {Abstract Vertical organic permeable base transistors (OPBT) can drive large current densities of kA cm−2 and achieve record-high transition frequencies of up to 40 MHz. They are therefore an interesting candidate for numerous applications, including the use in active-matrix organic light emitting display (AMOLED) backplanes. However, the transistor characteristics are required to be stable against electrical stress. Here, the threshold voltage shifts under current- and voltage-stress conditions over various temperatures and illumination conditions are investigated. OPBTs show excellent stability under the probed conditions, even at extended exposure to large on-state currents of 3 A cm−2. The strongest shifts are observed at elevated temperatures, suggesting a temperature activation of the stress effect. On-state current stress scales linearly with the current density, while off-state stress is induced by the applied voltage. The effects of both kinds of stress are complementary and can compensate each other. It is found that the OPBT is perfectly suitable as a switching transistor in AMOLED displays.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/aelm.201900548,

title = {Low-Voltage Operation of Ring Oscillators Based on Room-Temperature-Deposited Amorphous Zinc-Tin-Oxide Channel MESFETs},

author = {Oliver Lahr and Sofie Vogt and Holger von Wenckstern and Marius Grundmann},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aelm.201900548},

doi = {https://doi.org/10.1002/aelm.201900548},

year  = {2019},

date = {2019-01-01},

journal = {Advanced Electronic Materials},

volume = {5},

number = {12},

pages = {1900548},

abstract = {Abstract Schottky diode FET logic (SDFL) ring oscillator circuits comprising metal-semiconductor field-effect transistors (MESFETs) based on amorphous zinc-tin-oxide (ZTO) n-channels are presented. The ZTO channel layers are deposited entirely at room temperature by long-throw magnetron sputtering. Best MESFETs exhibit on/off current ratios as high as 8.6 orders of magnitude, a sub-threshold swing as low as 250 mV dec−1, and a maximum transconductance of 205 µS. Corresponding inverters show peakge gain magnitude (pgm) values of 83 with uncertainty levels as low as 0.5 V at an operating voltage of 5 V. Single stage delay times down to 277 ns are measured for three-stage ring oscillators, corresponding to oscillation frequencies as high as 451 kHz. Oscillations are observed at operating voltages as low as 3 V. These results prove the feasibility of room-temperature-deposited, amorphous semiconducting oxide based integrated circuits with SDFL layout. The presented approach provides more efficient as well as fail-safe device fabrication and similar oscillation frequencies at significantly lower operating voltages compared to conventional, high-temperature processed logic circuits based on insulating gates.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{https://doi.org/10.1002/adts.201800136,

title = {Machine Learning\textendashBased Charge Transport Computation for Pentacene},

author = {Jonas Lederer and Waldemar Kaiser and Alessandro Mattoni and Alessio Gagliardi},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adts.201800136},

doi = {https://doi.org/10.1002/adts.201800136},

year  = {2019},

date = {2019-01-01},

journal = {Advanced Theory and Simulations},

volume = {2},

number = {2},

pages = {1800136},

abstract = {Abstract Insight into the relation between morphology and transport properties of organic semiconductors can be gained using multiscale simulations. Since computing electronic properties, such as the intermolecular transfer integral, using quantum chemical (QC) methods requires a high computational cost, existing models assume several approximations. A machine learning (ML)\textendashbased multiscale approach is presented that allows to simulate charge transport in organic semiconductors considering the static disorder within disordered crystals. By mapping fingerprints of dimers to their respective transfer integral, a kernel ridge regression ML algorithm for the prediction of charge transfer integrals is trained and evaluated. Since QC calculations of the electronic structure must be performed only once, the use of ML reduces the computation time radically, while maintaining the prediction error small. Transfer integrals predicted by ML are utilized for the computation of charge carrier mobilities using off-lattice kinetic Monte Carlo (kMC) simulations. Benefiting from the rapid performance of ML, microscopic processes can be described accurately without the need for phenomenological approximations. The multiscale system is tested with the well-known molecular semiconductor pentacene. The presented methodology allows reproducing the experimentally observed anisotropy of the mobility and enables a fast estimation of the impact of disorder.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8629997,

title = {Hybrid Systems-in-Foil -Combining the Merits of Thin Chips and of Large-Area Electronics},

author = {J N Burghartz and G Alavi and B Albrecht and T Deuble and M Elsobky and S Ferwana and C Harendt and Y Mahsereci and H Richter and Z Yu},

doi = {10.1109/JEDS.2019.2896188},

issn = {2168-6734},

year  = {2019},

date = {2019-01-01},

journal = {IEEE Journal of the Electron Devices Society},

pages = {1-1},

abstract = {This paper reports on the status of a comprehensive ten-year research and development effort towards Hybrid System-in-Foil (HySiF). In HySiF, the merits of high-performance integrated circuits on ultra-thin chips and of large-area and discrete electronic component implementation are combined in a complementary fashion in and on a flexible carrier substrate. HySiF paves the way to entirely new applications of electronic products where form factor, form adaptivity and form flexibility are key enablers. In this review paper the various aspects of thin-chip fabrication and embedding, device and circuit design under impact of unknown or variable mechanical stress, and the on-and off-chip implementation of sensor, actuator, microwave and energy supply components are addressed.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8574943,

title = {High-Accuracy Localization and Calibration for 5-DoF Indoor Magnetic Positioning Systems},

author = {M Hehn and E Sippel and C Carlowitz and M Vossiek},

doi = {10.1109/TIM.2018.2884040},

issn = {0018-9456},

year  = {2019},

date = {2019-01-01},

journal = {IEEE Transactions on Instrumentation and Measurement},

pages = {1-11},

abstract = {Magnetic local positioning systems are a well-suited candidate for reliable indoor positioning systems, as they are robust against blocking by dielectric materials like walls or people. The system presented in this paper is implemented with a one-axis magnetic transmitter and several three-axis field sensors connected to a complete sensor network. Unfortunately, the performance of the system is severely impaired by field sensor nonidealities such as magnetic coupling of the sensor coils, coil misalignment, field sensor rotation, and unsynchronized sampling. In this paper, the overall field sensor impairments and an additive Gaussian noise model superposing the magnetic field are mathematically described. Then, a novel calibration scheme for the overall field sensor nonidealities is presented. Furthermore, a statistically optimal localization procedure coping with the field sensor nonidealities is developed. The proposed novel localization and calibration algorithms are demonstrated in a common office environment with a size of 7 m x 5 m x 3 m. Thereby, the calibration impressively reduces the position root-mean-square error (RMSE) from 46.8 to 10.6 cm and the angle RMSE from 24.8° to 6.1°.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/aelm.201900067,

title = {Solution Shearing of a High-Capacitance Polymer Dielectric for Low-Voltage Organic Transistors},

author = {Katherina Haase and Jakob Zessin and Konstantinos Zoumboulis and Markus M\"{u}ller and Mike Hambsch and Stefan C B Mannsfeld},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aelm.201900067},

doi = {10.1002/aelm.201900067},

year  = {2019},

date = {2019-01-01},

journal = {Advanced Electronic Materials},

volume = {5},

number = {6},

pages = {1900067},

abstract = {Abstract With the prospect of realizing innovative technologies by large-area fabrication at low cost and high throughput, printing and coating technologies are being intensively researched for the deposition of functional films. One promising coating technology is solution shearing, which has been studied as a deposition technique for organic semiconductors but not to a greater extent for dielectric layers. Therefore, the deposition by solution shearing of high-quality poly(4-vinylphenol) dielectrics is investigated, and the utility of these films as ultra-smooth dielectric substrates for transistors is demonstrated. By comparing these films to those prepared by spin-coating, it is possible to highlight the advantages of the technique. Specifically, thinner films with thicknesses as low as 11.4 nm but still low leakage and almost identical surface properties can be achieved. Thus, dielectric films with a very high capacitance of 280 nF cm-2 are realized in a single coating step. Probing these films within organic transistors shows that they can facilitate operation at voltages as low as -1 V. Finally, it is shown how the use of a polymer-small-molecule\textendashsemiconductor blend can pave the way toward high-performance, ultra-low-voltage devices from solution.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1002/adts.201800114,

title = {Impact of Phosphorescent Sensitizers and Morphology on the Photovoltaic Performance in Organic Solar Cells},

author = {Johannes Popp and Waldemar Kaiser and Alessio Gagliardi},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/adts.201800114},

doi = {10.1002/adts.201800114},

year  = {2019},

date = {2019-01-01},

journal = {Advanced Theory and Simulations},

volume = {2},

number = {1},

pages = {1800114},

abstract = {Abstract Phosphorescent sensitizers (PSs) are considered as a promising alternative for increasing the internal quantum efficiency (IQE) in organic solar cells (OSCs). By converting short-lifetime singlet into long-living triplet excitons, enhanced exciton diffusion and dissociation have been reported previously. However, only a limited increase in the OSC performance has been achieved. In this work, the interplay of the PS with both singlet and triplet excitons within organic blends is examined using kinetic Monte Carlo simulations including a comprehensive model of excitonic processes. Different morphologies of the conventional P3HT:PCBM solar cell are simulated, and the excitonic properties and their influence on the photovoltaic performance under doping are studied. The use of phosphorescent sensitization ensures high intersystem crossing and enlarges the diffusion length. An increase in the IQE of 34% is observed for a bilayer OSC. The increasing decay of triplets in proximity to the PS due to a strong spin-orbit coupling limits the IQE. Unlike expected, triplet-triplet annihilation does not provide a significant loss of excitons. A doped planar-mixed molecular heterojunction outperforms an undoped bulk-heterojunction OSC due to the enhanced exciton diffusion. A further study of optimal PS parameters predicts an increase in the IQE within bilayer solar cells by about 100%.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{M\"{u}nzenrieder30042019,

title = {Fabrication and AC Performance of Flexible Indium-Gallium-Zinc-Oxide Thin-Film Transistors},

author = {Niko M\"{u}nzenrieder and Giuseppe Cantarella and Luisa Petti},

url = {http://ecst.ecsdl.org/content/90/1/55.abstract},

doi = {10.1149/09001.0055ecst},

year  = {2019},

date = {2019-01-01},

journal = {ECS Transactions},

volume = {90},

number = {1},

pages = {55-63},

abstract = {The internet of things or foldable phones call for a variety of flexible sensor conditioning and transceiver circuits. However, the realization of high-performance, large-area, and deformable analog circuits is limited by the materials and the processes compatible with mechanically flexible substrates. Among the different semiconductors, InGaZnO is one of the most promising materials to realize high-frequency flexible thin-film transistors (TFTs) and circuits. In this work, the effect of different geometries, including self-aligned, vertical, and double-gate structures on the AC behaviour of flexible IGZO TFTs is presented. All TFTs are based on Al2O3 insulating layers, InGaZnO semiconductor, and polyimide substrates. The presented TFTs exhibit state-of-the-art performance including a field-effect mobility up to 15 cm2/Vs and a mechanical bendability down to radii of 3.5 mm. Due to different trade-offs required in the fabrication, flexible IGZO TFTs with the shortest channel length of 160 nm do not exhibit the highest measured frequency, whereas exceptional maximum oscillation and transit frequencies of 304 MHz and 135 MHz are demonstrated for 500 nm long self-aligned TFTs. Such optimized transistors can be used to realize entirely flexible analog circuits leading towards imperceptible electronic systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{doi:10.1021/acsaelm.9b00122,

title = {Flexible One-Dimensional Metal\textendashInsulator\textendashGraphene Diode},

author = {Zhenxing Wang and Burkay Uzlu and Mehrdad Shaygan and Martin Otto and M\'{a}rio Ribeiro and Enrique Gonz\'{a}lez Mar\'{i}n and Giuseppe Iannaccone and Gianluca Fiori and Mohamed Saeed Elsayed and Renato Negra and Daniel Neumaier},

url = {https://doi.org/10.1021/acsaelm.9b00122},

doi = {10.1021/acsaelm.9b00122},

year  = {2019},

date = {2019-01-01},

journal = {ACS Applied Electronic Materials},

volume = {1},

number = {6},

pages = {945-950},

abstract = {A novel one-dimensional geometry for metal\textendashinsulator\textendashgraphene (1D-MIG) diode with low capacitance is demonstrated. The junction of the 1D-MIG diode is formed at the 1D edge of Al2O3-encapsulated graphene with TiO2 which acts as barrier material. The diodes demonstrate ultrahigh current density since the transport in the graphene and through the barrier is in-plane. The geometry delivers very low capacitive coupling between the cathode and anode of the diode, which shows frequency response up to 100 GHz and ensures potential high-frequency performance up to 2.4 THz. The 1D-MIG diodes are demonstrated to function uniformly and stable under bending conditions down to 6.4 mm bending radius on flexible substrate.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Uzlu2019,

title = {Gate-tunable graphene-based Hall sensors on flexible substrates with increased sensitivity},

author = {Burkay Uzlu and Zhenxing Wang and Sebastian Lukas and Martin Otto and Max C Lemme and Daniel Neumaier},

doi = {10.1038/s41598-019-54489-0},

issn = {2045-2322},

year  = {2019},

date = {2019-01-01},

journal = {Scientific Reports},

volume = {9},

number = {1},

pages = {18059},

abstract = {We demonstrate a novel concept for operating graphene-based Hall sensors using an alternating current (AC) modulated gate voltage, which provides three important advantages compared to Hall sensors under static operation: (1) The sensor sensitivity can be doubled by utilizing both n- and p-type conductance. (2) A static magnetic field can be read out at frequencies in the kHz range, where the 1/f noise is lower compared to the static case. (3) The off-set voltage in the Hall signal can be reduced. This significantly increases the signal-to-noise ratio compared to Hall sensors without a gate electrode. A minimal detectable magnetic field Bmin down to $$290,rmnT/surd rmHz$$290nT/√Hz and sensitivity up to 0.55 V/VT was found for Hall sensors working on flexible polyimide (PI) substrates. This clearly outperforms state-of-the-art flexible Hall sensors and is comparable to the values obtained by the best rigid III/V semiconductor Hall sensors.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevApplied.10.044023,

title = {Quantitative Analysis of the Density of Trap States in Semiconductors by Electrical Transport Measurements on Low-Voltage Field-Effect Transistors},

author = {Michael Geiger and Lukas Schwarz and Ute Zschieschang and Dirk Manske and Jens Pflaum and J\"{u}rgen Weis and Hagen Klauk and Ralf Thomas Weitz},

url = {https://link.aps.org/doi/10.1103/PhysRevApplied.10.044023},

doi = {10.1103/PhysRevApplied.10.044023},

year  = {2018},

date = {2018-10-01},

journal = {Phys. Rev. Applied},

volume = {10},

pages = {044023},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8411327,

title = {Flexible In\textendashGa\textendashZn\textendashO Thin-Film Transistors With Sub-300-nm Channel Lengths Defined by Two-Photon Direct Laser Writing},

author = {L Petti and E Greco and G Cantarella and N M\"{u}nzenrieder and C Vogt and G Tr\"{o}ster},

doi = {10.1109/TED.2018.2851926},

issn = {0018-9383},

year  = {2018},

date = {2018-09-01},

journal = {IEEE Transactions on Electron Devices},

volume = {65},

number = {9},

pages = {3796-3802},

abstract = {In this paper, the low-temperature (≤150 °C) fabrication and characterization of flexible indium-gallium-zinc-oxide (IGZO) top-gate thin-film transistors (TFTs) with channel lengths down to 280 nm is presented. Such extremely short channel lengths in flexible IGZO TFTs were realized with a novel manufacturing process combining two-photon direct laser writing (DLW) photolithography with Ti/Au/Ti source/drain e-beam evaporation and liftoff. The resulting flexible IGZO TFTs exhibit a saturation field-effect mobility of 1.1 cm2· V-1· s-1and a threshold voltage of 3 V. Thanks to the short channel lengths (280 nm) and the small gate to source/drain overlap (5.2 μm), the TFTs yield a transit frequency of 80 MHz (at 8.5-V gate-source voltage) extracted from the measured S-parameters. Furthermore, the devices are fully functional when wrapped around a cylindrical rod with 6-mm radius, corresponding to 0.4% tensile strain in the TFT channel. These results demonstrate a new methodology to realize entirely flexible nanostructures and prove its suitability for the fabrication of short-channel transistors on polymer substrates for future wearable communication electronics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{8360966,

title = {Metal\textendashInsulator\textendashGraphene Diode Mixer Based on CVD Graphene-on-Glass},

author = {M Saeed and A Hamed and Z Wang and M Shaygan and D Neumaier and R Negra},

doi = {10.1109/LED.2018.2838451},

issn = {0741-3106},

year  = {2018},

date = {2018-07-01},

journal = {IEEE Electron Device Letters},

volume = {39},

number = {7},

pages = {1104-1107},

abstract = {In this letter, we present for the first time a mixer circuit based on Metal-Insulator-Graphene (MIG) diodes fabricated with large-scale monolayer graphene grown by chemical vapor deposition. A small-signal model extracted from the diode physical structure is used together with a large-signal model extracted from the dc characteristics of the MIG diode to build a down-conversion mixer. The measured conversion loss at a local oscillator power (PLO) of 5 dBm is lower than 15 dB, while RF-to-IF isolation is 36 dB with an input return loss and RF-to-LO isolation better than 10 dB over the frequency band from 1.7-6 GHz. Promising mixer results in combination with the CVD-based process promote the MIG diode-based mixer to be used in low-power, low-cost, microwave, and millimeter-wave circuit applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{PhysRevApplied.9.064001,

title = {Influence of Oxygen Deficiency on the Rectifying Behavior of Transparent-Semiconducting-Oxide--Metal Interfaces},

author = {Thorsten Schultz and Sofie Vogt and Peter Schlupp and Holger von Wenckstern and Norbert Koch and Marius Grundmann},

url = {https://link.aps.org/doi/10.1103/PhysRevApplied.9.064001},

doi = {10.1103/PhysRevApplied.9.064001},

year  = {2018},

date = {2018-06-01},

journal = {Phys. Rev. Applied},

volume = {9},

pages = {064001},

publisher = {American Physical Society},

keywords = {},

pubstate = {published},

tppubtype = {article}

}