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Funktionelle amorphe Dünnschichten: Bauelemente auf Basis von Zink-Zinn-OxidSchlupp, Peter 19 July 2018 (has links)
In der vorliegenden Arbeit werden Untersuchungen zu amorphen Zink-Zinn-Oxid Dünnschichten beschrieben. Unter anderem wurde eine Methode zur Herstellung von Dünnschichten mit lateralem Kompositionsgradienten mittels gepulster Laserabscheidung genutzt. Die untersuchten elektrischen und optischen Eigenschaften der Dünnschichten in Abhängigkeit vom Zink-Zinn-Verhältnis werden hier dargelegt und mit den Eigenschaften von Filmen verglichen, welche keinen Kompositionsgradienten haben.
Des Weiteren werden gleichrichtende Schottky-Kontakte diskutiert. Zunächst wird auf den Kontaktaufbau und die Auswahl des geeigneten Schottky-Metalls eingegangen. Dann wird die Modellierung des Stromtransports durch die Dioden vorgestellt. Mittels Defektspektroskopie gefundene Störstellenniveaus werden anschließend diskutiert.
Untersuchungen an mittels gepulster Laserabscheidung ausschließlich bei Raumtemperatur gezüchteten pn-Dioden, welche die p-leitenden Materialien Zink-Kobalt-Oxid bzw. Nickeloxid beinhalten, werden dargelegt. Hierbei wird neben der Optimierung der Herstellungsparameter die Nutzung von flexiblem Polyimid als Substrat diskutiert. Die hergestellten Dioden wurden verschieden starken Verbiegungen ausgesetzt, um zu testen, ob sie grundlegend für die Anwendung in flexiblen Schaltungen geeignet sind.
Im letzten Teil der Arbeit werden Untersuchungen an Sperrschicht-Feldeffekttransistoren beschrieben. Deren Gate-Struktur wird durch die vorher beschriebenen pn-Dioden realisiert. Es wird hierbei der Einfluss des Gate-Materials auf die Transistorkennlinien beschrieben. Zusätzlich werden auf den Transistoren basierende Inverterstrukturen diskutiert. Sowohl die Sperrschicht-Feldeffekttransistoren als auch die Inverter wurden außerdem auch auf flexiblen Substraten abgeschieden. Die Eigenschaften der Proben, bevor und nachdem
sie mechanischem Stress durch Verbiegen ausgesetzt wurden, werden in der Arbeit verglichen.
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Organic Electronic Devices - Fundamentals, Applications, and Novel ConceptsKleemann, Hans 11 December 2014 (has links) (PDF)
This work addresses two substantial problems of organic electronic devices: the controllability and adjustability of performance, and the integration using scalable, high resolution patterning techniques for planar thin-film transistors and novel vertical transistor devices. Both problems are of particular importance for the success of transparent and flexible organic electronics in the future.
To begin with, the static behavior in molecular doped organic pin-diodes is investigated. This allows to deduce important diode parameters such as the depletion capacitance, the number of active dopant states, and the breakdown field. Applying this knowledge, organic pin-diodes are designed for ultra-high-frequency applications and a cut-off-frequency of up to 1GHz can be achieved using optimized parameters for device geometry, layer thickness, and dopant concentration.
The second part of this work is devoted to organic thin-film transistors, high resolution patterning techniques, as well as novel vertical transistor concepts. In particular, fluorine based photo-lithography, a high resolution patterning technique compatible to organic semiconductors, is introduced fielding the integration of organic thin-film transistors under ambient conditions. However, as it will be shown, horizontal organic thin-film transistors are substantially limited in their performance by charge carrier injection. Hence, down-scaling is inappropriate to enlarge the transconductance of such transistors. To overcome this drawback, a novel vertical thin-film transistor concept with a vertical channel length of ∼50nm is realized using fluorine based photo-lithography. These vertical devices can surpass the performance of planar transistors and hence are prospective candidates for future integration in complex electronic circuits.
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A wired-AND transistor: Polarity controllable FET with multiple inputsSimon, M., Trommer, J., Liang, B., Fischer, D., Baldauf, T., Khan, M. B., Heinzig, A., Knaut, M., Georgiev, Y. M., Erbe, A., Bartha, J. W., Mikolajick, T., Weber, W. M. 29 November 2021 (has links)
Reconfigurable field effect transistors (RFET) have the ability to toggle polarity between n- and p- conductance at runtime [1], [2]. The here presented multiple independent gate (MIG) RFET expands the device functionality by offering additional logical inputs, valuable for e.g. efficient XOR or majority gate implementations [3], [4] or the here originally presented multiplexer circuit. Moreover,https://inspec.iet.org/ideas/#controlled-terms for the first time with a top-down RFET approach equal ON-currents are obtained for every configuration while requiring only one supply voltage (VDD).
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Junction tuning by ferroelectric switching in silicon nanowire Schottky-barrier field effect transistorsSessi, V., Mulaosmanovic, H., Hentschel, R., Pregl, S., Mikolajick, T., Weber, W. M. 07 December 2021 (has links)
We report on a novel silicon nanowire-based field effect transistor with integrated ferroelectric gate oxide. The concept allows tuning the carrier transport in a non-volatile approach by switching the polarization in the ferroelectric layer close to the source Schottky-junction. We interpret the results in terms of tuning the transmissibility of the Schottky-junction for charge carriers. The experimental results provide a first step towards the integration of memory-in-logic concepts with reconfigurable nanowire transistors.
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Demonstration of versatile nonvolatile logic gates in 28nm HKMG FeFET technologyBreyer, E. T., Mulaosmanovic, H., Slesazeck, S., Mikolajick, T. 08 December 2021 (has links)
Logic-in-memory circuits promise to overcome the von-Neumann bottleneck, which constitutes one of the limiting factors to data throughput and power consumption of electronic devices. In the following we present four-input logic gates based on only two ferroelectric FETs (FeFETs) with hafnium oxide as the ferroelectric material. By utilizing two complementary inputs, a XOR and a XNOR gate are created. The use of only two FeFETs results in a compact and nonvolatile design. This realization, moreover, directly couples the memory and logic function of the FeFET. The feasibility of the proposed structures is revealed by electrical measurements of HKMG FeFET memory arrays manufactured in 28nm technology.
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Realization and Characterization of Metal-Semiconductor Field-Effect Transistors based on Amorphous Zinc Tin OxideVogt, Sofie 10 August 2020 (has links)
Im ersten Teil der vorliegenden Arbeit werden die physikalischen Eigenschaften, insbesondere die elektrische Leitfähigkeit, von Zink-Zinn-Oxid Dünnschichten sowie darauf basierenden Schottky-Dioden in Abhängigkeit von der Kationenkomposition bestimmt. Zur Herstellung dieser Dünnschichten wurde ein Verfahren genutzt, welches die Herstellung von kontinuierlichen Kompositiongradienten im Rahmen eines gepulsten Laserabscheidungsprozesses bei Raumtemperatur ermöglicht. Erster Schwerpunkt der Diskussion ist die Abhängigkeit elektrischer Eigenschaften der Dünnschichten sowie die Diodeneigenschaften vom Kationenverhältnis. Des Weiteren wird die Langzeitstabilität der Schottky-Dioden und der Einfluss der Sauerstoffzufuhr während der Kontaktherstellung auf die Eigenschaften der Schottky-Dioden herausgestellt. DieErgebnissetiefenaufgelösterRöntgenphotoelektronenspektroskopiewerden diskutiert und ein Mechanismus, welcher zu einer Verbesserung der Schottky-Dioden über die Zeit führt, wird vorgestellt. Die Erkenntnisse über die optimale Kationenkomposition und den Einfluss des Sauerstoffs auf die Eigenschaften von Schottky-Dioden wurden genutzt, um Metall-Halbleiter-Feldeffekttransistoren herzustellen, welche im zweiten Teil der vorliegenden Arbeit beschrieben werden. In einem ersten Schritt wurden hierfür die Abscheidebedingungen in der Sputterkammer optimiert und eine neue Abscheiderezeptur für die Herstellung von Feldeffekttransistoren eingeführt. Auch hier finden alle Abscheidungen bei Raumtemperatur statt. Die Abscheidung mittels Sputtern wurde gewählt, da diese Abscheidemethode größere industrielle Relevanz als die gepulste Laserabscheidung hat. Metall-Halbleiter-Feldeffekttransistoren mit zwei verschiedenen Gate-Typen werden vorgestellt und jeweils der Einfluss der Kanalschichtdicke auf die Transistoreigenschaften untersucht. Der Einfluss des durch die Herstellung erzeugten Sauerstoffreservoirs in dem Schottky-Gate Kontakt auf die Eigenschaften der Feldeffekttransistoren wird ebenso gezeigt wie der Einfluss eines thermischen Ausheizprozesses auf die Schaltgeschwindigkeit der Feldeffekttransistoren. Außerdem werden einfache Inverter, welche auf zwei gleichartigen Feldeffekttransistoren basieren, vorgestellt. Ebenfalls werden SchottkyDioden Feldeffekttransistoren Logik basierte Inverter vorgestellt und charakterisiert. AbschließendwerdenRingoszillatoren,aufgebautausmehrereninReihegeschaltetenSchottkyDiodenFeldeffekttransistorenLogikbasiertenInverternvorgestellt. DerEinflussderKanalschichtdicke und der Gate-Geometrie auf die Oszillationsfrequenz wird diskutiert.:Contents
1 Introduction
2 Theoretical Descriptions
2.1 The Amorphous Semiconductor Zinc Tin Oxide
2.2 Schottky Barrier Diodes
2.3 Field-Effect Transistors
2.4 Inverter
2.5 Inverter Chain and Ring Oscillator
3 Methods
3.1 Growth and Structuring Techniques
3.1.1 Pulsed Laser Deposition
3.1.2 Sputtering Deposition
3.1.3 Photolithography
3.2 Characterization Techniques
3.2.1 Hall Effect Measurements
3.2.2 XRD and XRR Measurements
3.2.3 Static and Dynamic Current-Voltage Measurements
3.2.4 Further Characterization Techniques
4 Physical Properties of Amorphous Zinc Tin Oxide
4.1 Characterization of Pulsed Laser Deposited Zinc Tin Oxide Thin Films Having a Continuous Composition Spread
4.2 Properties of Schottky Barrier Diodes in Dependence on the Cation Composition
4.3 Long Term Stability of Schottky Barrier Diodes
4.4 ImportantRoleofOxygenfortheFormationofHighlyRectifyingContacts
4.5 Processes Governing the Long Term Stability
5 Demonstration and Characterization of Zinc Tin Oxide Based Devices
5.1 Implementation of a New Sputtering Recipe
5.1.1 CharacterizationandElectricalOptimizationoftheZincTinOxide Thin Films
.1.2 Optimization of the Gate Contact
5.2 Devices with PtOx/Pt Gate Contact
5.2.1 Variation of the Channel Thickness
5.2.2 Influence of the Oxygen Reservoir on the Performance and Long Term Stability of Devices
5.2.3 Tuning of the Electron Mobility
5.2.4 Frequency Dependent Switching of Transistors
5.3 Devices with i-ZTO/PtOx/Pt Gate Contact
5.3.1 Transistors with Varying Channel Thickness
5.3.2 Simple Inverter
5.3.3 SDFL Inverter
5.3.4 Inverter Chain
5.3.5 Ring Oscillators
5.4 Comparison to Literature
6 Summary and Outlook
Abbreviations
List of Symbols
Bibliography
List of Own and Contributed Articles
Appendix / In the first part of the present work the physical properties, especially the electrical properties, of zinc tin oxide thin films as well as Schottky diodes based thereon are determined as a function of the cation composition. For film growth, a room temperature pulsed laser deposition process was used, which allows the realization of a continuous composition gradient within one sample. First focus of the discussion is the dependence of electrical properties of thin films as well as diode properties on the cation ratio. Furthermore, the long-term stability of the Schottky diodes and the influence of the oxygen supply during contact fabrication on the properties of the Schottky diodes are highlighted. The results of depth-resolved Xray photoelectron spectroscopy measurements are discussed and a mechanism leading to an improvement of the Schottky diodes over time is elucidated. The findings on the optimal cation composition and the influence of oxygen on the properties of Schottky diodes were used to produce metal-semiconductor field-effect transistors, which are described in the second part of this thesis. In a first step, the deposition conditions in the sputter chamber were optimized and a new deposition recipe for the fabrication of field effect transistors was developed. Here, too, all depositions take place at room temperature. Sputter deposition was chosen because this deposition method has greater industrial relevance than pulsed laser deposition. Metal-semiconductor field-effect-transistors with two different gate types are presented and the influence of the channel layer thickness on the transistor properties is investigated. The influence of the oxygen reservoir in the Schottky gate contact on the properties of the field-effect-transistors is shown as well as the influence of a thermal annealing process on the switching speed of the field-effect-transistors. In addition, simple inverters based on two identical field-effect-transistors are demonstrated. Also Schottky diode field-effect-transistor logic based inverters are presented and characterized. Finally, ring oscillators consisting of several series-connected Schottky diode field-effecttransistor logic based inverters are presented. The influence of channel layer thickness and gate geometry on the oscillation frequency is discussed.:Contents
1 Introduction
2 Theoretical Descriptions
2.1 The Amorphous Semiconductor Zinc Tin Oxide
2.2 Schottky Barrier Diodes
2.3 Field-Effect Transistors
2.4 Inverter
2.5 Inverter Chain and Ring Oscillator
3 Methods
3.1 Growth and Structuring Techniques
3.1.1 Pulsed Laser Deposition
3.1.2 Sputtering Deposition
3.1.3 Photolithography
3.2 Characterization Techniques
3.2.1 Hall Effect Measurements
3.2.2 XRD and XRR Measurements
3.2.3 Static and Dynamic Current-Voltage Measurements
3.2.4 Further Characterization Techniques
4 Physical Properties of Amorphous Zinc Tin Oxide
4.1 Characterization of Pulsed Laser Deposited Zinc Tin Oxide Thin Films Having a Continuous Composition Spread
4.2 Properties of Schottky Barrier Diodes in Dependence on the Cation Composition
4.3 Long Term Stability of Schottky Barrier Diodes
4.4 ImportantRoleofOxygenfortheFormationofHighlyRectifyingContacts
4.5 Processes Governing the Long Term Stability
5 Demonstration and Characterization of Zinc Tin Oxide Based Devices
5.1 Implementation of a New Sputtering Recipe
5.1.1 CharacterizationandElectricalOptimizationoftheZincTinOxide Thin Films
.1.2 Optimization of the Gate Contact
5.2 Devices with PtOx/Pt Gate Contact
5.2.1 Variation of the Channel Thickness
5.2.2 Influence of the Oxygen Reservoir on the Performance and Long Term Stability of Devices
5.2.3 Tuning of the Electron Mobility
5.2.4 Frequency Dependent Switching of Transistors
5.3 Devices with i-ZTO/PtOx/Pt Gate Contact
5.3.1 Transistors with Varying Channel Thickness
5.3.2 Simple Inverter
5.3.3 SDFL Inverter
5.3.4 Inverter Chain
5.3.5 Ring Oscillators
5.4 Comparison to Literature
6 Summary and Outlook
Abbreviations
List of Symbols
Bibliography
List of Own and Contributed Articles
Appendix
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Micro- and tip-enhanced Raman spectroscopy of single-wall carbon nanotubes: from material studies to device applicationsKalbacova, Jana 21 December 2018 (has links)
Einwandige Kohlenstoffnanoröhrchen wurden aufgrund ihrer einzigartigen elektrischen, mechanischen und thermischen Eigenschaften 1991 in den Fokus der Forschung gerückt. In dieser Dissertation wird gezeigt, dass Ramanspektroskopie eine der besten Methoden ist, um die unterschiedlichen Eigenschaften der Nanoröhrchen wie ihren elektrischen Charakter (halbleitend oder metallisch), ihren Durchmesser, die Chiralität, Defekte oder auch Dotierung zu untersuchen. Die Charakterisierung dieser Eigenschaften wird sowohl für das reine Material als auch im elektrischen Bauteil, in diesem Fall einem Feldeffekttransistor, durchgeführt.
Der erste Teil der Arbeit vermittelt einen Überblick und gibt eine Einführung in Ramanspektroskopie und in die Struktur von Kohlenstoffnanoröhrchen. Es wird erklärt, welche Eigenschaften speziell mit Hilfe von Position und Intensität der Raman-Modi untersucht werden können und welche Aussagen über die Eigenschaften getroffen werden können. Im experimentellen Teil der Arbeit wurde eine Methode entwickelt, die eine rückstandslose Abscheidung von Dünnschichten aus Kohlenstoffnanoröhrchen ermöglicht. Die Quantifizierung von Defekten wurde durch die in den untersuchten Proben vorhandenen metallischen und halbleitenden Kohlenstoff-Nanoröhrchen ermöglicht. Mittels spitzenverstärkter Ramanspektroskopie wurden außerdem Defekte mit hoher Ortsauflösung (unterhalb von 10 nm) an einzelnen Nanoröhrchen charakterisiert. Der letzte Teil widmet sich den Eigenschaften in elektrische Bauteile, speziell Feldeffekttransistoren, die integrierten Kohlenstoffnanoröhrchen.:Bibliographische Beschreibung 3
Table of Contents 5
1 Introduction 7
2 Background 9
2.1 Structure of carbon nanotubes 9
2.2 Raman spectroscopy basics 10
2.3 Raman spectroscopy on graphene 14
2.4 Raman spectroscopy on carbon nanotubes 16
2.4.1 First-order Raman bands 18
2.4.2 Second-order Raman bands 20
2.5 How to analyze Raman spectra of single-wall carbon nanotubes 21
2.5.1 Diameter and chirality identification 22
2.5.2 Defect characterization 23
2.5.3 Doping and its connection to defects 25
2.5.4 Other effects that can cause frequency shifts 27
2.6 Tip-enhanced Raman spectroscopy 27
2.6.1 TERS experimental requirements 30
2.6.2 Tip and the signal enhancement 30
2.6.3 Brief summary of TERS on single-wall carbon nanotubes 31
3 Materials and Methods 33
3.1 Raman spectroscopy 33
3.2 Ion beam irradiation 34
3.3 SWCNT samples 35
3.4 SWCNT thin film preparation by vacuum filtration 36
3.5 Field effect transistor fabrication and electrical characterization 37
3.6 Tip-enhanced Raman spectroscopy 39
3.6.1 Preparation of the TERS tips 39
3.6.2 Instrumentation 39
3.6.3 SWCNT sample preparation 40
4 Preparation of carbon nanotube thin films 41
4.1 Removal of SDS 42
4.2 Removal of the density gradient medium 43
4.3 Summary 44
5 Quantifying defects in single-wall carbon nanotubes 45
5.1 Parameters of the defect creation 46
5.2 Reference measurement on ion irradiated graphite 47
5.3 Qualitative description of SWCNT defect development 48
5.3.1 Quantitative analysis of the SWCNT defects 57
5.3.2 Summary 59
6 Raman spectroscopy applied to investigate carbon nanotube transistors 61
6.1 Effect of chemical and thermal cleaning of SWCNTs 61
6.2 Effect of temperature and doping on SWCNTs in a Field-effect transistor 65
6.2.1 Investigation of temperature effect 66
6.2.2 In operando CNT-FET Raman spectroscopy measurement 67
6.3 Summary 71
7 TERS on SWCNTs 73
7.1 Preparation of TERS tips 73
7.1.1 Corrosion protection for silver TERS probes 73
7.2 Spatial resolution 76
7.3 Raman spectra of an individual nanotube at the nanoscale 77
7.4 Summary 81
8 Conclusions 83
References 85
Acknowledgement 97
Selbstständigkeitserklärung 99
Lebenslauf 101
Publication list 103
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Next Generation Ferroelectric Memories enabled by Hafnium OxideMikolajick, T., Schroeder, U., Lomenzo, P. D., Breyer, E. T., Mulaosmanovic, H., Hoffmann, M., Mittmann, T., Mehmood, F., Max, B., Slesazeck, S. 22 June 2022 (has links)
Ferroelectrics are theoretically an ideal solution for low write power nonvolatile memories. However, the complexity of ferroelectric perovskites has hindered the scaling of such devices to competitive feature sizes. The discovery of ferroelectricity in hafnium oxide solved this issue. Ferroelectric memories in three variants, capacitor based ferroelectric RAM, ferroelectric field effect transistors and ferroelectric tunneling junctions have become competitors for future memory solutions again. In this paper, the basics and current status of hafnium oxide based ferroelectric memory devices is described and recent results are shown.
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Semiconducting Organosilicon-based Hybrids for the Next Generation of Stretchable ElectronicsDitte, Kristina 12 May 2023 (has links)
During past years, organic-based electronic devices revealed high promise to supplement the ubiquitous silicon-based electronic devices and enable new fields of applications. At the center of this development is the considerable progress regarding π-conjugated polymer semiconductors (PSCs): Due to their processability from solution, light-weight, as well as low-cost, PSCs are now evolving towards production-scale of new technologies, e.g., in organic solar cells (OSCs), organic field-effect transistors (OFETs), and organic light emitting diodes (OLEDs). Especially OFETs are of fundamental importance, as they constitute the switching units in all logic circuits and display technologies.
However, the future world is expected to be full with smart electronics and communication devices integrated in clothes, tools and even interacting with the human body, e.g., as on-skin wearable sensors. For this the electrically-active material, just as a human tissue, requires to combine several properties in addition to being charge conducting: They need to show (i) mechanical softness, (ii) capacity to repair, (iii) multimodal sensitivity, as well as (iv) biodegradability. Here, PSCs still face challenges as they are brittle and break upon applying a mechanical stress. When trying to address this issue, the existing knowledge on mechanical properties of well-established polymeric plastics, e.g., polystyrene, cannot be directly applied for several reasons, e.g., (i) the bulkiness of monomers (including long side-chains), (ii) the rigid π-conjugated backbone, (iii) the low degree of polymerization, (iv) the small quantities in which PSCs are available, etc. Moreover, these kinds of materials should not only be mechanically compliant and stretchable, but furthermore retain their charge mobility upon stretching, and withstand numerous of mechanical stretching cycles. Considering this complex problem, researchers have been developing and investigating several approaches to combine good electrical properties and mechanical compliance within one material. These approaches include (i) stress-accommodating engineering, (ii) blending of PSCs into elastic matrix, as well as (iii) molecular engineering approach.
The latter seeks to interlink mechanical and electrical properties on the molecular level, i.e., synthesize polymers that are charge conducting and stretchable. Different strategies were tested, from the modification of side chains, to the introduction of conjugation breakings spacers into the backbone. Selected works sought to incorporate stretchability and conductivity by utilizing block copolymers, i.e., covalently linking a conjugated and a non-conjugated polymer chain, resulting in a phase separation of both constituents and preserving their respective properties.
The ultimate goal of this work is to achieve an intrinsically stretchable and electrically high-performing PSC via the block copolymer approach. This is done by connecting organosilicone, namely the polydimethylsiloxane (PDMS) elastomer – possessing outstanding mechanical properties, as well as good environmental and air stability – with a conjugated diketopyrrolopyrrole (DPP)-based donor-acceptor copolymer. The final obtained structure of this polymer is a tri-block copolymer (TBC) consisting of an inner DPP-based polymer block and two outer soft PDMS polymer blocks. The content of PDMS block can be controlled and be very high (up to 67 wt%), and easy processing, e.g., via shear coating, is possible. Relatively high charge carrier mobilities – in the same range as the reference DPP-based copolymer (i.e., without outer PDMS blocks) – are retained, and the block copolymers withstands numerous stretching cycles (up to 1500 cycles) without losing electrical functionality. Finally, one of the block copolymers was successfully incorporated into a biosensor for COVID-19 antibodies and antigens detection.
Overall, the findings of this work show that the block copolymer is a highly versatile approach to obtain functional and stretchable semiconductors with high charge carrier mobilities. Block copolymers consisting of a high-performing donor-acceptor PSC and a biocompatible elastomer could contribute towards one of the long-term goals of organic electronics – the realization of mechanically compliant materials for applications in stretchable electronics (e.g., wearable sensors, electronic skin, etc.).
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Toward Sustainable Transparent and Flexible Electronics with Amorphous Zinc Tin OxideLahr, Oliver 31 March 2023 (has links)
The present thesis addresses a sustainable approach to mechanically flexible and transparent electronic devices based on the amorphous oxide semiconductor zinc tin oxide (ZTO) as abundant and low-cost alternative to already industrially established materials such as amorphous indium gallium zinc oxide. ZTO thin films are deposited by radio frequency long-throw magnetron sputtering at room temperature to generally enable the implementation of common photolithography processes and further facilitate patterning of digital circuit elements on thermally unstable organic substrates.
Starting with the most basic device building blocks of integrated circuitry, various types of field-effect transistors are fabricated by implementation of amorphous ZTO
as active channel material. Metal-semiconductor field-effect transistors and pn heterodiode based junctions field-effect transistors as well as conventional metal-insulatorsemiconductor field-effect transistors are then compared regarding their electrical performance and long-term stability over a couple of months. A decisive step toward the successful interconnection of fundamental digital circuit elements, such as previously demonstrated simple inverters, is to ensure sufficient output level compatibility between the signals of associated logic components. Accordingly, the Schottky diode field-effect transistor logic approach is adapted for amorphous ZTO based devices in order to facilitate cascading of multiple inverters consisting of unipolar devices. Field-effect transistor properties as well as the circuit design have been continuously improved to enhance the overall performance in terms of functionality and low-voltage operation. Corresponding logic inverters are finally integrated in ring oscillator circuits to gain insights into the dynamic properties of digital circuit building blocks based on amorphous ZTO.
Ultimately, ZTO has been fabricated on mechanically flexible polyimide substrates
to determine the elastic and electrical properties of amorphous ZTO thin films in dependence on external tensile and compressive stress induced by mechanical bending. Further, associated flexible metal-semiconductor field-effect transistor are investigated regarding their performance stability under tensile strain. / Die vorliegende Arbeit umfasst die Herstellung und Charakterisierung aktiver elektrischer Bauelemente und integrierter Schaltkreise auf Basis des amorphen Oxidhalbleiters Zink-Zinnoxid (ZTO). Als vielversprechende nachhaltige und kostengünstigere Alternative zu dem bereits industriell etablierten Halbleiter Indium-Gallium-Zinkoxid wird insbesondere die Eignung von ZTO in optisch transparenter sowie mechanisch flexibler Elektronik untersucht. Um entsprechend Kompatibilität mit thermisch instabilen organischen Substraten sowie herkömmlichen Fotolithografieverfahren zu gewährleisten, beschränkt sich die Züchtung von ZTO-Dünnfilmen mittels Hochfrequenz-Magnetron-Distanzkathodenzerstäubung ausschließlich auf Herstellungsprozesse bei Raumtemperatur.
Zunächst wird auf die Umsetzung verschiedener Feldeffekttransistor-Typen auf
Basis amorphen ZTOs eingegangen, welche elektrisch charakterisiert und schließlich vor dem Hintergrund der Anwendung in integrierten Schaltkreisen vergleichend gegenübergestellt werden. Neben konventionellen Metall-Isolator-Halbleiterstrukturen wird vor allem näher auf Metall-Halbleiter-Feldeffekttransistoren sowie Sperrschicht-Feldeffekttransistoren auf der Grundlage von pn-Heteroübergängen eingegangen, da diese hauptsächlich in Bereichen hoher geforderter Schaltfrequenzen zum Einsatz kommen. Da integrierte Schaltkreise auf Basis unipolarer Feldeffekttransistoren eines Ladungsträgertyps inkonsistente Signaleingangs- sowie -ausgangspegel aufweisen, wird die Schottky- Dioden-Transistorlogik adaptiert, um entsprechend die Verknüpfung mehrerer Logikgatter auf Basis amorphen ZTOs zu gewährleisten. Durch geeignete Signalrückkopplung werden komplexere Schaltungen wie Ringoszillatoren realisiert, welche anhand von Laufzeitanalysen Aufschluss über die Schaltgeschwindigkeit ZTO basierter Feldeffekttransistoren geben.
Abschließend werden amorphe ZTO-Dünnfilme auf flexiblen Polyimid-Substraten
hergestellt und bezüglich der elastischen sowie elektrischen Eigenschaften in Abhängigkeit von exzessivem mechanischen Stress untersucht. Darüber hinaus werden flexible Metall-Halbleiter-Feldeffekttransistoren hinsichtlich ihrer Funktionalität und Stabilität gegenüber durch Biegeprozesse induzierte Verspannungen elektrisch charakterisiert.
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