Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices.

Printed electronics is simultaneously one of the most intensely studied emerging research areas in science and technology and one of the fastest growing commercial markets in the world today. For the past decade the potential for organic electronic (OE) materials to revolutionize this printed electronics space has been widely promoted. Such conviction in the potential of these carbon-based semiconducting materials arises from their ability to be dissolved in solution, and thus the exciting possibility of simply printing a range of multifunctional devices onto flexible substrates at high speeds for very low cost using standard roll-to-roll printing techniques. However, the transition from promising laboratory innovations to large scale prototypes requires precise control of nanoscale material and device structure across large areas during printing fabrication. Maintaining this nanoscale material control during printing presents a significant new challenge that demands the coupling of OE materials and devices with clever nanoscience fabrication approaches that are adapted to the limited thermodynamic levers available. In this review we present an update on the strategies and capabilities that are required in order to manipulate the nanoscale structure of large area printed organic photovoltaic (OPV), transistor and bioelectronics devices in order to control their device functionality. This discussion covers a range of efforts to manipulate the electroactive ink materials and their nanostructured assembly into devices, and also device processing strategies to tune the nanoscale material properties and assembly routes through printing fabrication. The review finishes by highlighting progress in printed OE devices that provide a feedback loop between laboratory nanoscience innovations and their feasibility in adapting to large scale printing fabrication. The ability to control material properties on the nanoscale whilst simultaneously printing functional devices on the square metre scale is prompting innovative developments in the targeted nanoscience required for OPV, transistor and biofunctional devices

Nanoestructurado de materia condensada blanda con aplicaciones en electrónica orgánica

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 21-10-2019Organic, light, flexible materials with functional properties as electrical conductivity and ferroelectricity that can be used in electronic devices are likely to be a safe bet for the future. However, these materials present much lower efficiencies compared with their analog inorganic materials. Therefore, a lot of research is still to be done to put organic materials in the competitive market. Nanostructuring is one of the most important approaches to achieve this objective, due in part to the requirement of miniaturization of electronic devices and because of the possibility of tuning the properties of these materials by modifying their structure at the nanoscale. This Thesis is focused on the fabrication of nanostructures on soft matter, mainly polymeric materials, with semiconducting and/or ferroelectric properties. Three kinds of nanostructures were fabricated: nanolayers or thin films (Chapter 3), surface nanostructures generated by laser irradiation (Chapter 4) and by nanoimprint lithography (Chapter 5), and nanoparticles (Chapter 6)...Los materiales orgánicos que presentan propiedades funcionales como la conductividad eléctrica y la ferroelectricidad, además de sus propiedades de ligereza y flexibilidad, son una apuesta segura para el futuro debido a la posibilidad de emplearlos en dispositivos electrónicos. Sin embargo, comparados con materiales inorgánicos análogos, presentan eficiencias mucho menores. Es por ello que aún debe realizarse un esfuerzo de investigación y desarrollo considerable, con el objetivo de colocar a estos materiales orgánicos en un nivel competitivo en el mercado. La nanoestructuración es uno de los caminos más investigados para conseguir este objetivo, no solo por la demanda actual de miniaturización de dispositivos electrónicos sino también por la posibilidad de modificar las propiedades funcionales de estos materiales mediante la alteración de su nanoestructura. Esta Tesis está enfocada a la fabricación y al estudio de nanoestructuras de materia condensada blanda, principalmente polímeros, con propiedades semiconductoras y/o ferroeléctricas. Se han fabricado tres tipos de nanoestructuras: nanocapas o películas delgadas (Capítulo 3), nanoestructuras superficiales mediante irradiación con láser (Capítulo 4) y nanoestructuras mediante litografía de nanoimpresión (Capítulo 5), así como nanopartículas (Capítulo 6).Fac. de Ciencias FísicasTRUEunpu

Interaction of ultrafast laser pulses with nanostructure surfaces

The interaction of ultrafast laser pulses with surfaces on the nanoscale paves the way for various innovative technologies in spectroscopy, photovoltaics, photocatalysis, or medicine, to mention only a few. The basic mechanisms, however, are still the subject of intense research. We take a closer look at this topic from different viewpoints. The first aspect is the enhancement of the efficiency of physical or chemical processes by producing local field maxima and resonances at top-down or bottom-up structured surfaces. A further aspect is the dynamic change of optical properties by inducing free carriers and plasmons. Last but not least, permanent nanostructures can be obtained as a result of nano-feedback and self-organization. In high-energy laser physics, all three aspects play a role at once. Therefore, particular attention will be paid to this emerging field

Magnetic imaging of 3D artificial spin-ice structures

This thesis is a meticulous journey into the realm of three-dimensional Artificial Spin Ices (ASI), pushing the boundaries of exploration beyond the familiar territories of two dimensions. Employing methodologies like two-photon lithography and thermal evaporation, it navigates the intricate landscape of diamond-bond lattice geometries, unveiling emergent behaviours such as monopole propagation. Section 3 meticulously charts the ASI structure's three-dimensional phase diagram, comparing predictive Monte Carlo simulations with experimental observations. The diversity of predicted phases, from double-charged monopole crystals to conventional spin ice, is scrutinized through magnetic force microscopy (MFM), revealing new vertex types and providing data for comparisons with simulations. Discrepancies between anticipated and observed ground states are attributed to an effective chemical potential (μ^*) and limitations in the deterministic demagnetisation protocol. Ferromagnetic dominance on the upper surface layer and a higher μ^* for monopole formation impede the anticipated double-charged crystal, except in localized disorder regions. Recommendations for modifying the topography of the surface layer are proposed to realize this state. Delving deeper into the system, x-ray magnetic circular dichroism (XMCD) is suggested to probe layers with a 1-unit cell thickness, expanding comprehension. Future plans involve transforming the 3D ASI into a thermally dynamic system, challenging for measurement techniques like MFM due to state perturbation and extended times. Section 4 delves into synchrotron-based techniques, notably transmission X-ray microscopy with XMCD, affirming permalloy nanowire structures' crescent-shaped cross-section. Refinements in fabrication methods, despite revealing oxidization of the magnetic coating, offer nuanced insights into magnetic behaviours within the 3D ASI. XMCD measurements hint at weak signals, particularly in SL2, suggesting the need for further fabrication refinements and envisioning polymer-free magnetic nanowire-based 3D ASI designs for future exploration. In a meticulous journey through ASI's three-dimensional landscapes, this thesis unearths complexities, proposes modifications, and sets the stage for deeper explorations into emergent phenomena

In-situ Gas Phase Catalytic Properties Of Metal Nanoparticles

Recent advances in surface science technology have opened new opportunities for atomic scale studies in the field of nanoparticle (NP) catalysis. The 2007 Nobel Prize of Chemistry awarded to Prof. G. Ertl, a pioneer in introducing surface science techniques to the field of heterogeneous catalysis, shows the importance of the field and revealed some of the fundamental processes of how chemical reactions take place at extended surfaces. However, after several decades of intense research, fundamental understanding on the factors that dominate the activity, selectivity, and stability (life-time) of nanoscale catalysts are still not well understood. This dissertation aims to explore the basic processes taking place in NP catalyzed chemical reactions by systematically changing their size, shape, oxide support, and composition, one factor at a time. Low temperature oxidation of CO over gold NPs supported on different metal oxides and carbides (SiO2, TiO2, TiC, etc.) has been used as a model reaction. The fabrication of nanocatalysts with a narrow size and shape distribution is essential for the microscopic understanding of reaction kinetics on complex catalyst systems ( real-world systems). Our NP synthesis tools are based on self-assembly techniques such as diblock-copolymer encapsulation and nanosphere lithography. The morphological, electronic and chemical properties of these nanocatalysts have been investigated by atomic force microscopy (AFM), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD). Chapter 1 describes briefly the basic principles of the instrumentation used within this experimental dissertation. Since most of the state-of-art surface science characterization tools provide ensemble-averaged information, catalyst samples with well defined morphology and structure must be available to be able to extract meaningful information on how size and shape affect the physical and chemical properties of these structures. In chapter 2, the inverse-micelle encapsulation and nanosphere lithography methods used in this dissertation for synthesizing uniformly arranged and narrow size- and shape-selected spherical and triangular NPs are described. Chapter 3 describes morphological changes on individual Au NPs supported on SiO2 as function of the annealing temperature and gaseous environment. In addition, NP mobility is monitored. Chapter 4 explores size-effects on the electronic and catalytic properties of size-selected Au NPs supported on a transition metal carbide, TiC. The effect of interparticle interactions on the reactivity and stability (catalyst lifetime) of Au NPs deposited on TiC is discussed in chapter 5. Size and support effects on the formation and thermal stability of Au2O3, PtO and PtO2 on Au and Pt NPs supported on SiO2, TiO2 and ZrO2 is investigated in chapter 6. Emphasis is given to gaining insight into the role of the NP/support interface and that played by oxygen vacancies on the stability of the above metal oxides. Chapter 7 reports on the formation, thermal stability, and vibrational properties of mono- and bimetallic AuxFe1-x (x = 1, 0.8, 0.5, 0.2, 0) NPs supported on TiO2(110). At the end of the thesis, a brief summary describes the main highlights of this 5-year research program

Chemical Lithography with Monomolecular Templates

Motivation für diese Arbeit was die Entwicklung einer neuen Präparationsmethode, um eine Einzelstrang-DNA (engl.: single stranded DNA, ssDNA ) innerhalb eines biokompatiblen Templats zu immobilisieren und zudem ssDNA-Muster beliebiger Form und Größe herzustellen. Als Ansatz wurde eine strahlungsinduzierte Austauschreaktion (engl.: irradiation promoted exchange reaction, IPER) im Rahmen des konzepts der Chemischen Lithographie verwendet. IPER ermöglicht es mittels Elektronenbestrahlung, das Ausmaß der Austauschreaktion zwischen einer primären, das Substrat bedeckenden selbstorganisierten Monoschicht (engl.: self-assembled monolayer, SAM ) und einem molekularen Substituent je nach Dosis zu steuern. Physikalisch bedeutet IPER die Erzeugung von chemischen und strukturellen Defekten in dem primären SAM, die die Austauschreaktion fördern. Im dieser Arbeit wurde der IPER Ansatz auf eine kontrollierte und ortsspezifische Immobilisierung von ssDNA auf Au(111)-Substraten erweitert. Um eine unspezifische Adsorption außerhalb der ssDNA bedeckten Bereiche zu verhindern, wurde als Ausgangsmatrix eine biokompatible Oligoethylenglykol-substituierte Alkanthiol (OEG-AT) Monolage verwendet. Im ersten Abschnitt wurden thiol-terminierte ssDNA als Substituenten eingesetzt. IPER mit diesen Substituenten und einem OEG-AT-SAM als Vorlage führten zu homogen gemischten ssDNA/OEG-AT Filmen der gewünschten Zusammensetzung, die anhand der eingestellten Dosis angepasst werden konnte. Basierend auf diesen Ergebnissen wurde IPER mit Elektronenstrahllithographie (EBL) verwendet, was die Herstellung komplexer ssDNA-Muster mit der gewünschten Form und Nanometergröße (bis zu 25-50 nm) innerhalb der biokompatiblen Matrix erlaubte. Diese Muster wurden dann als Vorlagen für die oberflächeninitiierte, enzymatische Polymerisation (SIEP) eingesetzt, was die Präparation von komplexen, räumlichen ssDNA Bürsten erlaubte. Ausgehend von den genannten Ergebnissen wurde die Möglichkeit überprüft, IPER mit kommerziell verfügbaren ssDNA-Disulfid Substituenten durchzuführen. Zunächst wurde eine Studie unter Verwendung eines Referenzfilms aus einem nicht-substituierten AT auf Gold und einem symmetrischen COOH-substituierten Dialkyldisulfid als Substituent durchgeführt. Dabei wurde festgestellt, dass IPER mit Disulfid-Substituenten in der gleichen Weise wie mit Thiolen durchgeführt werden kann. Es konnte gezeigt werden, dass die Kinetik der Austauschreaktion in beiden Fällen ähnlich ist, wenn auch das Ausmaß der Reaktion bei den Disulfiden geringer war. Dennoch konnten gemischten SAMs mit einer Konzentration der substituenten Spezies von bis zu 60% hergestellt werden. Basierend auf diesen Ergebnissen wurde die Möglichkeit verschiedener symmetrischer wie asymmetrischer ssDNA-Disulfide als Substituenten für IPER untersucht, wobei beide Systeme sich als geeignet für die IPER erwiesen. Die asymmetrischen Disulfide zeigten ähnlich hohe Wirkungsgrade, während die Effizienz der symmetrischen Disulfide insbesondere bei niedrigen Bestrahlungsdosen (< 0,6 mC/cm² ) deutlich niedriger war. Die Verwendung von IPER erfordert Hochvakuum und im Fall komplexer Strukturierung aufwändige Versuchsaufbauten wie Rasterelektronenmikroskop. Daher wurde in einem weiteren Abschnitt UV-Licht als Initiator für die Austauschreaktion zwischen der primären OEG-AT Matrix und den ssDNA Substituenten eingesetzt. UV-Licht wurde zur homogenen und lithographischen Strukturierung, zur Herstellung gemischter ssDNA/OEG-AT Filme und ssDNA Muster eingebetten in eine biokompatible OEG-AT Matrix verwendet. Auch hierbei konnte die Zusammensetzung der gemischten Filme durch die Wahl der Dosis eingestellt werden. Es wurde auch gezeigt, dass das UV-Licht unterschiedlicher Wellenlängen (254 oder 365 nm) neue Möglichkeiten für die Lithographie eröffnet. Zuletzt wurde eines der Systeme, ssDNA Polymerbürsten gekoppelt an ein monomolekulares ssDNA Templat, im Rahmen dieser Arbeit detailliert untersucht. Eine Kombination von mehreren komplementären spektroskopische Techniken wurde verwendet, um die chemische Integrität, Reinheit und molekulare Ausrichtung dieser mittels SIEP hergestellten Objekte zu untersuchen. Die Spektren der Polymerbürsten waren nahezu identisch mit denen der monomolekularen ssDNA Vorläufer und wiesen keine Spuren von Verunreinigungen auf. Neben der wohldefinierten chemischen Integrität und dem kontaminationsfreien Charakter, zeigten die Bürsten eine vergleichsweise hohe Orientierungsordnung, mit vorzugsweise aufrechter Ausrichtung der einzelnen Stränge. Die entwickelten Herstellungsmethoden beiten die Möglichkeit, ssDNA/OEG–AT Filme und Muster für die Bindung und den Nachweis der komplementär ssDNA Stränge sowie für die Erkennung von DNA-bindenden Proteinen zu präparieren, was unter anderem eine Grundlage für Sensorfabrikation bildet. Ferner dienen sie als vielseitige Plattform für Nanofabrikation, wie anhand der komplexen ssDNA Bürste in dieser Arbeit demonstriert wurde

Nanoestructuración y propiedades de superficies de polímeros con aplicaciones en energía

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 21/11/2016The integration of functional polymers in organic electronics has attracted great interest for their potential application in photovoltaics or diodes due to their characteristics such as high chemical tenability, low temperature processing, light weight and durability, among others. The incorporation of polymers into nowadays devices, that tend towards miniaturization, rises several challenges. In general, the macroscopic properties of polymers are closely related to their structure, that is hierarchical, from the nanometer to the millimeter scale. Hence, from a fundamental viewpoint, understanding the effect of the above mentioned miniaturization in the structure and physical phenomena would provide control over the properties of the nanoscaled polymer materials, helping in the design of new potential applications. In this Thesis we have attempted to fulfill the objective of preparing binary systems formed by pairs of functional polymers or pairs of organics materials, and understanding the modification of certain polymer properties when nanostructuring them, mainly in their surfaces. For the preparation of these binary systems we employed different methodologies: direct solution blending (Chapter 3, blends of donor/acceptor organic compounds, Chapter 4, blends of semiconducting and ferroelectric polymers), bilayer structures from semiconducting/ ferroelectric polymers, prepared by sequential spin coating (Chapter 4) and nanostructuring of a ferroelectric polymer in the form of nanospheres to be incorporated in a semiconducting polymer film (Chapter 4). In Chapter 3, the conduction mechanism and the molecular dynamics on a bulk heterojunction formed by a binary blend of donor/acceptor organic compounds have been studied by dielectric spectroscopy. In Chapter 4, the modification of the ferroelectric properties in poly(vinylidene fluoride- trifluoroethylene) copolymers due to nanostructuring and to the combination with a semiconducting polymer have been addressed by Piezoresponse force microscopy. Nanostructured functional polymer surfaces were prepared by laser techniques, mainly Laser Induced Periodic Surface Structures (LIPSS). In Chapter 5, we first report on the creation of LIPSS on a model polymer: polystyrene...La integración de polímeros funcionales en la electrónica orgánica es de gran interés por su potencial aplicación en dispositivos fotovoltaicos y diodos, debido principalmente a características tales como la alta resistencia química, la posibilidad de procesado a baja temperatura, su ligereza y durabilidad, entre otras. La incorporación de polímeros en los dispositivos actuales que tienden a la miniaturización afronta varios retos. En general, las propiedades macroscópicas de polímeros están estrechamente relacionadas con su estructura, que es jerárquica desde la escala de los nanómetros a la milimétrica. Por lo tanto, desde el punto de vista fundamental, comprender el efecto de la mencionada miniaturización en la estructura y los fenómenos físicos de estos polímeros proporcionaría control sobre las propiedades de los materiales poliméricos incorporados en dispositivos ayudando al diseño de nuevas aplicaciones potenciales. En esta Tesis hemos tratado de cumplir con el objetivo de preparar sistemas binarios formados por pares de polímeros funcionales o pares de materiales orgánicos, y comprender las variaciones de ciertas propiedades del polímero cuando se nanoestructura, sobre todo cuando se crean superficies nanoestructuradas. Para la preparación de estos sistemas binarios se emplearon diferentes metodologías: la mezcla directa en solución (Capítulo 3, mezclas de los compuestos orgánicos donadores / aceptores, Capítulo 4, mezclas de polímeros semiconductores y ferroeléctricos), las estructuras de dos capas de polímeros semiconductores / ferroeléctricos, preparadas por ‘spin coating’ secuencial (Capítulo 4) y nanoestructuración de polímero ferroeléctrico en forma de nanoesferas que se incorpora a una película de polímero semiconductor (Capítulo 4). En lo que se refiere al estudio de procesos físicos fundamentales en estos sistemas, en el Capítulo 3, el mecanismo de conducción y la dinámica molecular en una heterounión en volumen formada por la mezcla de compuestos orgánicos donador / aceptor se ha estudiado mediante espectroscopia dieléctrica. En el Capítulo 4, la modificación de las propiedades ferroeléctricas en copolímeros al azar de poli(fluoruro de vinilideno) y poli(trifluoroetileno) debida a nanoestructuración y a la combinación con polímeros semiconductores han sido abordadas por Microscopía de Piezorespuesta...Fac. de Ciencias FísicasTRUEunpu

The 2017 Terahertz Science and Technology Roadmap

Science and technologies based on terahertz frequency electromagnetic radiation (100GHz-30THz) have developed rapidly over the last 30 years. For most of the 20th century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to “real world” applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2016, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 17 sections that cover most of the key areas of THz Science and Technology. We hope that The 2016 Roadmap on THz Science and Technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies