DNA nanotechnology has developed a versatile set of methods to utilise DNA self-assembly for the bottom-up construction of arbitrary two- and three-dimensional DNA objects in the nanometre size range, and to functionalise the structures with unprecedented site-specificity with nanoscale objects such as metallic and semiconductor nanoparticles, proteins, fluorescent dyes, or synthetic polymers. The advances in structure assembly have resulted in the application of functional DNA-based nanostructures in a gamut of fields from nanoelectronic circuitry, nanophotonics, sensing, drug delivery, to the use as host structure or calibration standard for different types of microscopy. However, the analytical means for characterising DNA-based nanostructures drag behind these advances. Open questions remain, amongst others in quantitative single-structure evaluation. While techniques such as atomic force microscopy (AFM) or transmission electron microscopy (TEM) offer feature resolution in the range of few nanometres, the number of evaluated structures is often limited by the time-consuming manual data analysis. This thesis has introduced two new approaches to quantitative structure evaluation using AFM and super-resolution fluorescence microscopy (SRM). To obtain quantitative data, semi-automated computational image analysis routines were tailored in both approaches. AFM was used to quantify the attachment yield and placement accuracy of poly(3-tri(ethylene glycol)thiophene)-b-oligodeoxynucleotide diblock copolymers on a rectangular DNA origami. This work has also introduced the first hybrid of DNA origami and a conjugated polymer that uses a highly defined polythiophene derivative synthesised via state-of-the-art Kumada catalyst-transfer polycondensation. Among the AFM-based studies on polymer-origami-hybrids, this was the first to attempt near-single molecule resolution, and the first to introduce computational image analysis. Using the FindFoci tool of the software ImageJ revealed attachment yields per handle between 26 - 33%, and determined a single block copolymer position with a precision of 80 - 90%. The analysis has pointed out parameters that potentially influence the attachment yield such as the handle density and already attached objects. Furthermore, it has suggested interactions between the attached polymer molecules. The multicolour SRM approach used the principles of single-molecule high-resolution co-localisation (SHREC) to evaluate the structural integrity and the deposition side of the DNA origami frame “tPad” based on target distances and angles in a chiral fluorophore pattern the tPads were labelled with. The computatinal routine that was developed for image analysis utilised clustering to identify the patterns in a sample’s signals and to determine their characteristic distances and angles for hundreds of tPads simultaneously. The method excluded noise robustly, and depicted the moderate proportion of intact tPads in the samples correctly. With a registration error in the range of 10 -15 nm after mapping of the colour channels, the precision of a single distance measurements on the origami appeared in the range of 20 - 30 nm. By broadening the scope of computational AFM image analysis and taking on a new SRM approach for structure analysis, this work has presented working approaches towards new tools for quantitative analysis in DNA nanotechnology. Furthermore, the work has presented a new approach to constructing hybrid structures from DNA origami and conjugated polymers, which will open up new possibilities in the construction of nanoelectronic and nanophotonic structures.

Small cantilevers with ultra-high resonant frequencies (1–3 MHz) have paved the way for high-speed atomic force microscopy. However, their potential for multi-frequency atomic force microscopy is unexplored. Because small cantilevers have small spring constants but large resonant frequencies, they are well-suited for the characterisation of delicate specimens with high imaging rates. We demonstrate their imaging capabilities in a bimodal frequency modulation mode in constant excitation on semi-crystalline polypropylene. The first two flexural modes of the cantilever were simultaneously excited. The detected frequency shift of the first eigenmode was held constant for topographical feedback, whereas the second eigenmode frequency shift was used to map the local properties of the specimen. High-resolution images were acquired depicting crystalline lamellae of approximately 12 nm in width. Additionally, dynamic force curves revealed that the contrast originated from different interaction forces between the tip and the distinct polymer regions. The technique uses gentle forces during scanning and quantified the elastic moduli Eam = 300 MPa and Ecr = 600 MPa on amorphous and crystalline regions, respectively. Thus, multimode measurements with small cantilevers allow one to map material properties on the nanoscale at high resolutions and increase the force sensitivity compared with standard cantilevers. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

This thesis reports on the controlled formation of surface rippling structures induced by tip scanning processes on compliant and brittle materials. Periodic surface structures were generated on polymeric and vitreous materials and with different length scales. Two aspects were focused on: the controlling of orientation and periodicity of the resulting structures via proper tuning the scan conditions and the physical mechanisms ruling the early stages of plowing wear causing the rippling effect. Specifically the influence of the scanned area geometric shape on the orientation of the rippling structure was investigated on a polystyrene surface. Nanoripples were induced by scanning the surface with a silicon tip using atomic force microscopy and dedicated scripts. Inside a structured area two ripple orientations can be observed: near boundaries the ripple orientation is determined by boundary orientation and regions away from the boundaries the ripples are aligned in a steady orientation. This steady orientation can be tuned by the distance between the scan lines. In the boundary regions the orientation of the ripples is different from steady orientation. The orientation of the boundaries clearly affected the orientation of the ripples and the tendency of the ripples to align in a steady angle defined by the scan parameters could be significantly modified. Geometric shapes like squares, circles, stars, pentagons and hearts allowed to distinguish the influence of curved and straight boundaries. Straight boundaries with different orientations allowed a detailed analysis of the influence of the angle on the rippling process. Straight boundaries inclined in the direction of the steady state angle of ripple orientation previously defined generate a uniform ripple pattern covering the entire scan area. The aspect of wear originating from the rippled surface was also investigated on similar polystyrene surfaces. As a result of repetitive scan passes spherical particles with diameters up to 250 nm were nucleated and detached from the surface. The particles originate from the crests of the ripples formed in the first scan pass. As proven by the lateral force signal the detachment occurs smoothly without a static friction peak suggesting a crazing mechanism induced by the scanning tip. Once detached from the surface the particles are displaced and piled up along the edges of scanned area. The formation of periodic surface structures was also investigated on a brittle silica glass. By a combination of scratch tests performed with a diamond microtip mounted in a nanoindenter and imaging with atomic force microscopy the existence of a periodic herringbone pattern inside scratch grooves on silica glass was proven. The rippled pattern was induced in the scratch process when the indenter was pulled laterally along the surface resulting in a microscopic scratch groove. The load was varied up to 30 nN and the scan velocity up to 500 µm/s. The resulting periodicity of the structures was found to increase linearly with increasing scratch velocity. The repetition distance was in the range of sub-µm and the corrugation in the range of a few hundred nm, which was well below indentation depth. In both cases, the surface rippling on a polymeric surfaces and the formation of a periodic pattern inside microscratches on a glass surface, the results were found to be consistent with minimalistic theoretical models for stick-slip.:Contents i Abstract iii Zusammenfassung v 1. Introduction 1 1.1. Periodic surface structures – relevance and formation 1 1.2. Surface rippling created by scanning probe lithography 2 1.3. Wear and nanoparticle release 4 1.4. Aim and outline 4 2. Experimental methods and fundamental concepts 6 2.1. Nanolithography 6 2.2. Atomic force microscopy 7 2.3. Nanoindentation and -scratching 10 2.4. Wear 11 2.5. Stick-slip motion 12 2.6. Spin coating 14 3. Surface rippling on polystyrene 15 3.1. Background and motivation 15 3.2. Methods 20 3.2.1. Sample preparation 20 3.2.2. Scanning probe lithography process 20 3.2.3. Imaging of structures and nanoparticles 21 3.3. Effect of boundaries on the orientation of surface rippling 22 3.4. Particle release as a result of surface rippling 31 4. Periodic structures inside scratches on silica glass 37 4.1. Background and motivation 37 4.2. Methods 38 4.2.1. Sample preparation 39 4.2.2. Scratch tests 39 4.2.3. AFM imaging and analysis 39 4.3. Surface rippling induces by scraping with a sharp indenter 40 5. Conclusion and outlook 49 A. Appendix surface rippling on polymers I B. Appendix surface rippling on glass IV Acknowledgements VII References IX

Relatively little is known about the folding and stability of membrane proteins. Conventional thermal or chemical unfolding techniques probe the average behavior of large numbers of molecules and thus cannot resolve co-existing minor and major unfolding pathways and intermediates. Here, I applied single-molecule force measurements based on an atomic force microscope (AFM) to characterize the stability of the membrane protein bacteriorhodopsin (BR). In these mechanical unfolding experiments, an external pulling force played the role of the denaturant and lead to unfolding of the three-dimensional structure of individual proteins. It was found that single BRs unfold step-wise in a well-defined sequence of stable intermediates and in different unfolding pathways. Although single [alpha]-helices were sufficiently stable to unfold in individual steps they also exhibited certain probabilities to unfold in pairs. These observations support the "two-stage" and the "helical-hairpin" model of membrane protein folding. Dynamic force measurements showed that [alpha]-helices and helical hairpins are relatively rigid structures, which are stabilized by narrow energy barriers and have stabilities between 100-10?000 seconds. These forced unfolding experiments were complemented with the development of new force measurement techniques. It is demonstrated that hydrodynamic effects need to be considered to obtain more complete kinetic pictures of single molecules. In addition, two force spectroscopy approaches to measure the complex visco-elastic response of single molecules are presented and applied to BR. These experiments revealed that the unfolding patterns of single proteins are dominated by purely elastic polypeptide extension and determined the dissipative interactions associated with the unfolding of single [alpha]-helices. In addition, it was found that kinks result in a reduced unfolding cooperativity of [alpha]-helices.

Ein zentraler Nachteil der meisten Koordinationspolymere ist, dass sie elektrische Isolatoren sind. In dieser Arbeit wurden konjugierte Koordinationspolymere auf ihre Leitfähigkeit untersucht, die eine Rhodium-Paddle-Wheel-Struktur besitzen. Die Beschichtung auf einer funktionalisierten Oberfläche im Vorfeld der C-AFM-Messung wurde mittels eines selbstgebauten Dip-Coaters realisiert. Koordinationspolymere, die das [Rh2(ac)4]-Paddle-Wheel enthalten, sind unabhängig von den untersuchten Linkern Isolatoren. Werden die Acetatliganden mit drei oder vier Acetamidatliganden ausgetauscht, so ist das entstandene Koordinationspolymer leitfähig. Temperaturabhängige C-AFM-Messungen ergeben eine für hohe Feldstärken konstante Aktivierungsenergie, die je nach Koordinationspolymer zwischen 0,3 eV und 0,7 eV beträgt. Anhand der Ergebnisse wurde gezeigt, dass der Ladungstransport durch einen Hopping Mechanismus dominiert wird. C-AFM ist eine aussagekräftige Methode zur Charakterisierung leitfähiger Koordinationspolymere auf der Oberfläche.

Ziel dieser Arbeit war die Entwicklung neuer Methoden in der Rasterkraftmikroskopie, um die Qualität und Interpretierbarkeit von Oberflächenabbildungen auf der Nanometerskala, vor allem jener sehr weicher Proben, entscheidend zu verbessern. Der für polymere und biologische Materialien standardmäßig verwendete intermittierende Kontaktmodus führt auf weichen Oberflächen zu verfälschten Abbildungen der Topographie und der mechanischen Eigenschaften. In dieser Arbeit wurden Techniken entwickelt, die einerseits zerstörungsfreie, tiefenaufgelöste Rasterkraftmikroskopie und andererseits Einzelmessungen mit variabler Dämpfung im intermittierenden Kontaktmodus ermöglichen. Die laterale Auflösung beider Methoden liegt dabei im Rahmen herkömmlicher Techniken (< 10 nm). Die Tiefenauflösung konnte im Vergleich zu anderen Methoden um eine Größenordnung auf unter 1 nm verbessert werden. Die neuen Methoden wurden auf einer breiten Palette polymerer Materialien angewandt. Die räumliche Struktur oberflächennaher Bereiche eines Blockcopolymerfilms konnte im Vergleich zu herkömmlichen Methoden deutlich genauer abgebildet werden. Gleiches wurde auf elastomerem Polypropylen erreicht. Es konnten weiche, amorphe Deckschichten auf teilkristallinen Polymeren nachgewiesen und vermessen werden, was in der organischen Elektronik eine wichtige Rolle spielen kann. Die innere Struktur selbstangeordneter Nanodrähte aus Oligothiophen-Aggregaten konnte aufgelöst werden und es wurde die Selbstanordnung von Kollagenfibrillen im gequollenen Zustand beobachtet.

Switching of surface composition and morphology of binary polymer brushes in response to changes in solvent selectivity, heating above glass transition temperatures, and contact with a rubbery stamp was studied. The binary brushes: polystyrene/poly(2-vinyl pyridine) (PS/P2VP), poly(styrene-co-2,3,4,5,6-pentafluorostyrene)/poly(methyl (meth)acrylate) (PSF/P(M)MA), and PS/PMMA were synthesized via two-step surface-initiated radical polymerization. Wetting experiments show that switching of brushes? surface composition upon exposure to solvents of various thermodynamic quality occurs faster than in 6 s. It takes longer time (5-10 min), if rate of solvent diffusion into the brush film is low. Discontinuous switching of surface composition of binary brushes is found upon exposure to binary solvents with gradually changed selectivity. X-ray Photoelectron Spectroscopy (XPS) shows quantitatively that the top brush layer (1) is dominated by respective favourite polymers after exposure to solvents of opposite selectivity and (2) comprises both brush constituents in almost symmetric ratio after exposure to non-selective solvents. Morphologies of binary brushes obtained after exposure to the solvents were studied with Atomic Force Microscopy (AFM). Local top layer composition was sensed with X-ray Photoemission Electron Microscopy (XPEEM). The morphologies are relevant to the particular solvents, reproducible, and independent on previous solvents. Phase segregation beneath the brush top layers was visualized with plasma etching. Qualitative agreement of the experimentally observed morphologies and predicted with self-consistent field theory is found. Enrichment of a binary brush top layer with the polymer providing lower surface energy takes place after annealing. Perpendicular segregation of binary brush constituents was sensed with XPEEM on perpendicular walls of imprinted elevations after wet microcontact printing.

Die Ferroelektrische Lithografie ist ein im letzten Jahrzehnt entwickeltes Verfahren zur gezielten Steuerung des Aufbaus von Nanostrukturen auf ferroelektrischen Oberflächen. Hierbei wird ausgenutzt, dass die unterschiedlich orientierte Spontanpolarisation des Materials in den einzelnen Domänen zu einer charakteristischen Variation der Oberflächenchemie führt. Die vorliegende Dissertation behandelt die Umsetzung dieses Ansatzes zur gezielten und steuerbaren Deposition von Nanostrukturen aus Edelmetallen oder organischen Molekülen. Diese Deposition erfolgte mittels einer nasschemischen Prozessierung unter UV-Beleuchtung auf magnesiumdotierten, einkristallinen Lithiumniobat-Substraten. Als typisches Ergebnis zeigte sich sowohl für in Wasser gelöste Silber-, Gold- und Platinsalze als auch für wässrige Lösungen des organischen Fluoreszenzfarbstoffs Rhodamin 6G eine bevorzugte Abscheidung des Materials an den 180°-Domänenwänden auf der Substratoberfläche. Dabei beginnt die Abscheidung in Form einzelner Nanopartikel innerhalb eines 150−500 nm breiten Streifens parallel zur Domänenwand. Bei fortgesetzter Beleuchtung erfolgt ein weiteres Wachstum der Kristallite bis zur ihrer gegenseitigen Berührung. Damit ermöglicht dieser Abscheideprozess den Aufbau organischer oder metallisch polykristalliner Nanodrähte mit Abmessungen um 100 nm in Breite und Höhe. Die Länge ist lediglich durch die Probenabmessungen begrenzt. Die so erzeugten Strukturen wurden im Rahmen der experimentellen Arbeiten topografisch, elektrisch und optisch charakterisiert. Am Beispiel einzeln kontaktierter Platindrähte konnte dabei deren annähernd ohmsches Leitfähigkeitsverhalten nachgewiesen werden. Zudem reagiert der Widerstand eines solchen Platin-Nanodrahtes sehr sensitiv auf Änderungen des umgebenden Gasmediums, was die Eignung solcher Strukturen für die Integration in künftige Sensorbauelemente unterstreicht. Weitergehende Untersuchungen beschäftigten sich mit der Klärung der Ursachen dieser sogenannten Domänenwanddekoration. Hierzu wurde die Lage der abgeschiedenen Strukturen mit dem zu Grunde liegenden Domänenmuster verglichen. Bis auf wenige Ausnahmen wurde dabei eine auf die Domänengrenze zentrierte, symmetrische Bedeckung nachgewiesen. Als Erklärungsansatz wird die Trennung der photoinduzierten Elektron-Loch-Paare durch das elektrostatische Feld der Polarisations- und Abschirmladungen diskutiert. Diese führt zur Ladungsträgerakkumulation und erhöhten chemischen Reaktivität an den Domänengrenzen. / Ferroelectric lithography is a method for a controlled assembly of nanostructures on ferroelectric surfaces, which has has been established throughout the last decade. It exploits the characteristic variations in surface chemistry arising from the different orientations of the spontaneous polarisation within the separate domains. The scope of this thesis is the application of that approach for the directed and controlled deposition of nanostructures consisting of noble metals or organic molecules. For this deposition, a wet chemical processing under UV illumination was carried out on magnesium doped lithium niobate single crystals. As a typical result, the decoration of 180° domain walls was observed for aqueous solutions of silver, gold and platinum salts as well as for the dissolved organic fluorescent dye Rhodamine 6G. The deposition starts within a stripe of 150−500 nm in width parallel to the domain wall. Under continuing illumination, the crystallites grow further until they finally touch each other. Using this technique, organic or metallic polycrystalline nanowires with dimensions in the range of 100nm in width and height can be assembled. Their length is only limited by the sample size. These nanostructures were characterised in respect of their topographical, electrical and optical properties. In the case of contacted single platinum wires an electrical conduction was measured, which showed approximately ohmic behaviour. It was also shown that the resistance of such a platinum nanowire is very sensitive to changes in the surrounding gas medium. This emphasises the suitability of such structures for integration in future sensor devices. Further experiments were carried out to investigate the physical background of the observed domain wall decoration. For this, the positions of the deposited structures were compared with the underlying domain structure. Apart from few exceptions, a symmetric deposition centered at the domain wall was observed. As a starting point for explanation, the separation of electron-hole-pairs by the electrostatic field from polarisation and screening charges is discussed. This process leads to charge carrier accumulation at the domain boundaries, thus enhancing the local chemical reactivity.

(ULSI) causes an increase of the resistance of the wiring system by increased scattering of electrons at side walls and grain boundaries in the state of the art Cu technology, which increases the RC delay of the interconnect system and thus degrades the performance of the device. The outstanding properties of carbon nanotubes (CNT) such as a large mean free path, a high thermal conductance and a large resistance against electromigration make them an ideal candidate to replace Cu in future feature nodes. The present thesis contributes to the preparation and properties of CNT based vertical interconnections (vias). In addition, all processes applied during the fabrication are compatible to ULSI and an interface between CNT based vias and a Cu metallization is studied. The methodology for the evaluation of CNT based vias is improved; it is highlighted that by measuring the resistance of one multiwall CNT and taking into account the CNT density, the performance of the CNT based vias can be predicted accurately. This provides the means for a systematic evaluation of different integration procedures and materials. The lowest contact resistance is obtained for carbide forming metals, as long as oxidation during the integration is avoided. Even though metal-nitrides exhibit an enhanced contact resistance, they are recommended to be used at the bottom metallization in order to minimize the oxidation of the metal-CNT contact during subsequent processing steps. Overall a ranking for the materials from the lowest to the highest contact resistance is obtained: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Furthermore the impact of post CNT growth procedures as chemical mechanical planarization, HF treatment and annealing procedures after the CNT based via fabrication are evaluated. The conductance of the incorporated CNTs and the applicable electrical transport regime relative to the CNT quality and the CNT length is discussed. In addition, a strong correlation between the temperature coefficient of resistance and the initial resistance of the CNT based vias at room temperature has been observed. / Die kontinuierliche Miniaturisierung der charakteristischen Abmessungen in hochintegrierten Schaltungen (ULSI) verursacht einen Anstieg des Widerstandes im Zuleitungssystem aufgrund der erhöhten Streuung von Elektronen an Seitenwänden und Korngrenzen in der Cu-Technologie, wodurch die Verzögerungszeit des Zuleitungssystems ansteigt. Die herausragenden Eigenschaften von Kohlenstoffnanoröhren (CNT), wie eine große mittlere freie Weglänge, hohe thermische Leitfähigkeit und eine starke Resistenz gegenüber Elektromigration machen diese zu einem idealen Kandidaten, um Cu in zukünftigen Technologiegenerationen zu ersetzen. Die vorliegende Arbeit beschreibt die Herstellung und daraus resultierenden Eigenschaften von Zwischenebenenkontakten (Vias) basierend auf CNTs. Alle verwendeten Prozessierungsschritte sind kompatibel mit der Herstellung von hochintegrierten Schaltkreisen und eine Schnittstelle zwischen den CNT Vias und einer Cu-Metallisierung ist vorhanden. Insbesondere das Verfahren zur Evaluierung von CNT Vias wurde durch den Einsatz verschiedener Methoden verbessert. Insbesondere soll hervorgehoben werden, dass durch die Messung des Widerstandes eines einzelnen CNTs, bei bekannter CNT Dichte, der Via Widerstand sehr genau vorausgesagt werden kann. Dies ermöglicht eine systematische Untersuchung des Einflusses der verschiedenen Prozessschritte und der darin verwendeten Materialien auf den Via Widerstand. Der niedrigste Kontaktwiderstand wird für Karbidformierende Metalle erreicht, solange Oxidationsprozesse ausgeschlossen werden können. Obwohl Metallnitride einen höheren Kontaktwiderstand aufweisen, sind diese für die Unterseitenmetallisierung zu empfehlen, da dadurch die Oxidation der leitfähigen Schicht minimiert wird. Insgesamt kann eine Reihenfolge beginnend mit dem niedrigsten zum höchsten Kontaktwiderstand aufgestellt werden: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Desweiteren wurde der Einfluss von Verfahren nach dem CNTWachstum wie die chemischmechanische Planarisierung, eine HF Behandlung und einer Temperaturbehandlung evaluiert, sowie deren Einfluss auf die elektrischen Parameter des Vias untersucht. Die Leitfähigkeit der integrierten CNTs und die daraus resultierenden elektrischen Transporteigenschaften in Abhängigkeit der CNT Qualität und Länge werden besprochen. Ebenso wird die starke Korrelation zwischen dem Temperaturkoeffizienten des elektrischen Widerstandes und des Ausgangswiderstandes der CNT basierten Vias bei Raumtemperatur diskutiert.

In dieser Arbeit werden organische Feldeffekttransistoren (OFETs) aus den verschiedenen Materialien Manganphthalocyanin (MnPc), [6,6]Phenyl-C61-butansäuremethylester (PCBM), 6,13-Bis(triisopropylsilyethinyl)pentacen (TIPS-Pentacen) und N,N’- Bis(n-octyl)-1,6-Dicyanoperylen-3,4:9,10-Bis(Dicarboximid) (PDI8-CN2) hergestellt. Dabei finden unterschiedliche Abscheidemethoden wie die Molekularstrahlabscheidung, die Ultraschallsprühbeschichtung und die Drehbeschichtung Anwendung. Die Morphologie sowie die Funktionsweise der Transistoren werden in Abhängigkeit von den Herstellungsparametern und bezüglich ihrer Stabilität gegenüber Lufteinfluss und elektrischer Belastung charakterisiert. Durch Aufdampfen von MnPc konnten so zum ersten Mal ambipolare MnPc-OFETs hergestellt und charakterisiert werden. Die bestimmten Löcher- und Elektronenbeweglichkeiten bestätigen die Eignung von MnPc für die Anwendung in Spintronik-Bauelementen. Desweiteren wird anhand gesprühter PCBM- und TIPS-Pentacen-OFETs gezeigt, dass die Ultraschallsprühbeschichtung eine geeignete Technik ist, um organische Halbleiter aus Lösung für die Verwendung in OFETs abzuscheiden. Die Abscheidung organischer Filme lässt sich mit einer Vielzahl an Parametern beeinflussen und die Funktionsweise von OFETs optimieren. In Verbindung mit den Untersuchungen aufgeschleuderter PDI8-CN2-OFETs konnte ein erheblicher Einfluss der Oberflächenenergie des verwendeten SiO2-Gateisolators auf die Korngröße im organischen Film festgestellt werden.