Optical microcavities (OMs) are receiving increasing attention owing to their potential applications ranging from cavity quantum electrodynamics, optical detection to photonic devices. Recently, rolled-up structures have been demonstrated as OMs which have gained considerable attention owing to their excellent customizability. To fully exploit this customizability, asymmetric and topological rolled-up OMs are proposed and investigated in addition to conventional rolled-up OMs in this thesis. By doing so, novel phenomena and applications are demonstrated in OMs. The fabrication of conventional rolled-up OMs is presented in details. Then, dynamic mode tuning by a near-field probe is performed on a conventional rolled-up OM. Next, mode splitting in rolled-up OMs is investigated. The effect of single nanoparticles on mode splitting in a rolled-up OM is studied. Because of a non-synchronized oscillating shift for different azimuthal split modes induced by a single nanoparticle at different positions, the position of the nanoparticle can be determined on the rolled-up OM. Moreover, asymmetric rolled-up OMs are fabricated for the purpose of introducing coupling between spin and orbital angular momenta (SOC) of light into OMs. Elliptically polarized modes are observed due to the SOC of light. Modes with an elliptical polarization can also be modeled as coupling between the linearly polarized TE and TM mode in asymmetric rolled-up OMs. Furthermore, by adding a helical geometry to rolled-up structures, Berry phase of light is introduced into OMs. A -π Berry phase is generated for light in topological rolled-up OMs so that modes have a half-integer number of wavelengths. In order to obtain a deeper understanding for existing rolled-up OMs and to develop the new type of rolled-up OMs, complete theoretical models are also presented in this thesis.

The presence of photonic band gap in an arbitrarily shaped photonic structure, particularly structures that are fabricated by exploiting rolled-up nanotechnology, can be understood from the density of optical states. In this thesis, the density of optical states and the local density of optical states in finite-sized photonic structures are calculated using the finite difference time domain method together with a parallelized message passing interface. With this approach, a software package suitable for high-performance computing on multi-platform was published under GNU GPL license. When light is guided to propagate along a rolled-up thin film, whispering gallery mode resonances can be formed in a microtubular structure. Dynamic probing and tuning via a plasmonic nanoparticle-coated glass tip are investigated to demonstrate the transition from dielectric-dielectric to dielectric-plasmonic coupling in the tubular microcavity. The competition of these two coupling mechanisms allow the tuning of the optical cavity modes towards lower and then higher energies in a single coupling system. Moreover, three dimensionally confined higher order axial modes can be selectively coupled and tuned by the glass tip due to their unique spatial distribution of the optical field along the tube axis. In addition, the interaction between sharp optical cavity modes and broad plasmonic modes supported by silver nanoparticles leads to the occurrence of Fano resonance. In particular, Fano resonances occurring at higher-order axial modes has been observed as well. The experimental results are supported by numerical simulations based on the finite difference time domain method. In photonic lattice structures, light propagation behavior can be influenced and defined by the photonic band structure. By designing the unit cell with glide mirror symmetry, topologically protected edge states operating in the visible spectral range have been proposed in two dimensional photonic crystals which can be made of feasible materials. Topological phenomena such as unidirectional waveguiding and/or effective zero refractive index are presented. In addition, a scheme to study topological phase transition in a single photonic crystal device is proposed and studied via unevenly stretching photonic lattice. Moreover, a new method is explored to distinguish the topological phase from the bulk modes. The research presented in this thesis concerns molding the flow of light in specially designed photonic devices for various potential applications. The software package can be used to design and investigate finite-sized photonic structures with an arbitrary shape, which is much faster in terms of computation than other reported techniques and software packages. The rolled-up microcavities can be employed to trap and store light in the way of whispering gallery mode resonances, and the resonant light can be tuned and modulated by a plasmonic nanoparticles-coated glass tip. This research is particularly interesting for optical signal processing, slowing light via Fano resonances, and high sensitive sensing. In addition, the topological photonic crystal design and examination scheme presented in this thesis provide a simplified yet more efficient way to obtain non-trivial topological phase from a tunable photonic crystal that can be verified not only by edge modes but also by bulk modes.:Bibliographic record 1 Abstract 1 LIST OF ABBREVIATIONS and Symbols 3 1 Introduction 9 1.1 Introduction and Motivation 9 1.2 Objectives 11 1.3 Organization of the thesis 12 2 Density of optical states in rolled-up photonic crystals and quasi crystals 15 2.1 Introduction 15 2.1.1 background 17 2.1.2 Infinitely extended ideal photonic crystal 17 2.2 Finite-sized photonic crystal, photonic quasicrystal, and arbitrary photonics structures 20 2.2.1 Numerical algorithm 25 2.2.2 Rolled-up photonic crystals and quasi crystals 30 2.3 Software package 33 2.3.1 Computational performance 33 2.3.2 FPS User interface 35 2.3.3 Detailed tutorial 37 2.3.4 Alternative rolled-up photonic crystals 47 2.3.5 Beyond 3D photonic crystals. 48 2.4 Conclusion 49 3 Rolled-up microesonator 51 3.1 Introduction 51 3.2 Rolled-up microresonators 52 4 Tip-assisted photon-plasmon coupling in three-dimensionally confined microtube cavities 57 4.1 Introduction 57 4.2 Tube and plasmonic particle preparation and characterization 60 4.3 Results and discussion 62 4.4 Axial mode tuning 64 4.5 Fano resonance 65 4.5.1 Background 65 4.5.2 Fano resonance in the tip assisted coupling setup 68 4.6 Conclusion 71 5 Topological photonics 73 5.1 Introduction and motivation 73 5.2 Topological phase transition point 77 5.2.1 Fundamental phase transition point 77 5.2.2 Zero refractive index material 79 5.3 Non-trivial topology in realistic materials 80 6 Topological phase transition in stretchable photonic crystals 85 6.1 Introduction and motivation 85 6.2 SSH model 88 6.3 Photonic crystal 91 6.4 Band structure and end modes of the photonic crystal 99 6.5 Conclusion 101 7 Summary and outlook 103 7.1 Summary 103 7.2 Outlook 104 Bibliography 111 List of figures 127 Publications 133 Acknowledgments 136 Selbständigkeitserklärung 137 Curriculum Vitae 138

Structure-property quantification of an A36 steel alloy was the focus of this study in order to calibrate and validate a plasticity-damage model. The microstructural parameters included grain size, particle size, particle number density, particle nearest neighbor distances, and percent of ferrite and pearlite. The mechanical property data focused on stress-strain behavior under different applied strain rates (0.001/s, 0.1/s, and 1000/s), different temperatures (293 K and 573 K), and different stress states (compression, tension, and torsion). Notch tension tests were also conducted to validate the plasticity-damage model. Also, failure of an A36 I-beam was examined in cyclic loads, and the crack growth rates were quantified in terms of fatigue striation data. Dynamic strain aging was observed in the stress-strain behavior giving rise to an important point that there exists a critical temperature for such behavior.

Die Menschheit steht vor der großen Herausforderung der Energieversorgung des 21. Jahrhundert. Nirgendwo ist diese noch dringlicher geworden als im Bereich der Energiespeicherung und Umwandlung. Konventionelle Energie kommt hauptsächlich aus fossilen Brennstoffen, die auf der Erde nur begrenzt vorhanden sind, und hat zu einer starken Belastung der Umwelt geführt. Zusätzlich nimmt der Energieverbrauch weiter zu, insbesondere durch die rasante Verbreitung von Fahrzeugen und verschiedener Kundenelektronik wie PCs und Mobiltelefone. Alternative Energiequellen sollten vor einer Energiekrise entwickelt werden. Die Gewinnung erneuerbarer Energie aus Sonne und Wind sind auf jeden Fall sehr wichtig, aber diese Energien sind oft nicht gleichmäßig und andauernd vorhanden. Energiespeichervorrichtungen sind daher von großer Bedeutung, weil sie für eine Stabilisierung der umgewandelten Energie sorgen. Darüber hinaus ist es eine enttäuschende Tatsache, dass der Akku eines Smartphones jeglichen Herstellers heute gerade einen Tag lang ausreicht, und die Nutzer einen zusätzlichen Akku zur Hand haben müssen. Die tragbare Elektronik benötigt dringend Hochleistungsenergiespeicher mit höherer Energiedichte. Der erste Teil der vorliegenden Arbeit beinhaltet Lithium-Ionen-Batterien unter Verwendung von einzelnen aufgerollten Siliziumstrukturen als Anoden, die durch nanotechnologische Methoden hergestellt werden. Eine Lab-on-Chip-Plattform wird für die Untersuchung der elektrochemischen Kinetik, der elektrischen Eigenschaften und die von dem Lithium verursachten strukturellen Veränderungen von einzelnen Siliziumrohrchen als Anoden in einer Lithium-Ionen-Batterie vorgestellt. In dem zweiten Teil wird ein neues Design und die Herstellung von flexiblen on-Chip, Festkörper Mikrosuperkondensatoren auf Basis von MnOx/Au-Multischichten vorgestellt, die mit aktueller Mikroelektronik kompatibel sind. Der Mikrosuperkondensator erzielt eine maximale Energiedichte von 1,75 mW h cm-3 und eine maximale Leistungsdichte von 3,44 W cm-3. Weiterhin wird ein flexibler und faserartig verwebter Superkondensator mit einem Cu-Draht als Substrat vorgestellt. Diese Dissertation wurde im Rahmen des Forschungsprojekts GRK 1215 "Rolled-up Nanotechnologie für on-Chip Energiespeicherung" 2010-2013, finanziell unterstützt von der International Research Training Group (IRTG), und dem PAKT Projekt "Elektrochemische Energiespeicherung in autonomen Systemen, no. 49004401" 2013-2014, angefertigt. Das Ziel der Projekte war die Entwicklung von fortschrittlichen Energiespeichermaterialien für die nächste Generation von Akkus und von flexiblen Superkondensatoren, um das Problem der Energiespeicherung zu addressieren. Hier bedanke ich mich sehr, dass IRTG mir die Möglichkeit angebotet hat, die Forschung in Deutschland stattzufinden. / Human beings are facing the grand energy challenge in the 21st century. Nowhere has this become more urgent than in the area of energy storage and conversion. Conventional energy is based on fossil fuels which are limited on the earth, and has caused extensive environmental pollutions. Additionally, the consumptions of energy are still increasing, especially with the rapid proliferation of vehicles and various consumer electronics like PCs and cell phones. We cannot rely on the earth’s limited legacy forever. Alternative energy resources should be developed before an energy crisis. The developments of renewable conversion energy from solar and wind are very important but these energies are often not even and continuous. Therefore, energy storage devices are of significant importance since they are the one stabilizing the converted energy. In addition, it is a disappointing fact that nowadays a smart phone, no matter of which brand, runs out of power in one day, and users have to carry an extra mobile power pack. Portable electronics demands urgently high-performance energy storage devices with higher energy density. The first part of this work involves lithium-ion micro-batteries utilizing single silicon rolled-up tubes as anodes, which are fabricated by the rolled-up nanotechnology approach. A lab-on-chip electrochemical device platform is presented for probing the electrochemical kinetics, electrical properties and lithium-driven structural changes of a single silicon rolled-up tube as an anode in lithium ion batteries. The second part introduces the new design and fabrication of on chip, all solid-state and flexible micro-supercapacitors based on MnOx/Au multilayers, which are compatible with current microelectronics. The micro-supercapacitor exhibits a maximum energy density of 1.75 mW h cm-3 and a maximum power density of 3.44 W cm-3. Furthermore, a flexible and weavable fiber-like supercapacitor is also demonstrated using Cu wire as substrate. This dissertation was written based on the research project supported by the International Research Training Group (IRTG) GRK 1215 "Rolled-up nanotech for on-chip energy storage" from the year 2010 to 2013 and PAKT project "Electrochemical energy storage in autonomous systems, no. 49004401" from 2013 to 2014. The aim of the projects was to design advanced energy storage materials for next-generation rechargeable batteries and flexible supercapacitors in order to address the energy issue. Here, I am deeply indebted to IRTG for giving me an opportunity to carry out the research project in Germany. September 2014, IFW Dresden, Germany Wenping Si

Rolled-up nanotechnology based on strain-engineering is a powerful tool to manufacture three-dimensional hollow structures made of virtually any kind of material on a large variety of substrates. The aim of this thesis is to address the key features of different on- and off-chip applications of rolled-up microtubes through modification of their basic framework. The modification of the framework pertains to the tubular structure, in particular the diameter of the microtube, and the material which it is made of, hence achieving different functionalities of the final rolled-up structure. The tuning of the microtube diameter which is adjusted to the individual size of an object allows on-chip studies of single cells in artificial narrow cavities, for example. Another modification of the framework is the addition of a catalytic layer which turns the microtube into a self-propelled catalytic micro-engine. Furthermore, the tuneability of the diameter can have applications ranging from nanotools for drilling into cells, to cargo transporters in microfluidic channels. Especially rolled-up microtubes based on low-cost and easy to deposit materials, such as silicon oxides, can enable the exploration of novel systems for several scientific topics. The main objective of this thesis is to combine microfluidic features of rolled-up structures with optical sensor capabilities of silicon oxide microtubes acting as optical ring resonators, and to integrate these into a Lab-on-a-Chip system. Therefore, a new concept of microfluidic integration is developed in order to establish an inexpensive, reliable and reproducible fabrication process which also sustains the optical capabilities of the microtubes. These integrated microtubes act as optofluidic refractrometric sensors which detect changes in the refractive index of analytes using photoluminescence spectroscopy. The thesis concludes with a demonstration of a functional portable sensor device with several integrated optofluidic sensors. / Die auf verspannten Dünnschichten basierende „rolled-up nanotechnologie“ ist eine leistungsfähige Methode um dreidimensionale hohle Strukturen (Mikroröhrchen) aus nahezu jeder Art von Material auf einer großen Vielfalt von Substraten herzustellen. Ausgehend von der Möglichkeit der Skalierung des Röhrchendurchmessers und der Modifikation der Funktionalität des Röhrchens durch Einsatz verschiedener Materialien und Oberflächenfunktionalisierungen kann eine große Anzahl an verschiedenen Anwendungen ermöglicht werden. Eine Anwendung behandelt unter anderem on-chip Studien einzelner Zellen wobei die Mikroröhrchen, an die Größe der Zelle angepasste, Reaktionscontainer darstellen. Eine weitere Modifikation der Funktionalität der Mikroröhrchen kann durch das Aufbringen einer katalytischen Schicht realisiert werden, wodurch das Mikroröhrchen zu einem selbstangetriebenen katalytischen Mikro-Motor wird. Hauptziel dieser Arbeit ist es Mikrometer große optisch aktive Glasröhrchen herzustellen, diese mikrofluidisch zu kontaktieren und als Sensoren in Lab-on-a-Chip Systeme zu integrieren. Die integrierten Glasröhrchen arbeiten als optofluidische Ringresonatoren, welche die Veränderungen des Brechungsindex von Fluiden im inneren des Röhrchens durch Änderungen im Evaneszenzfeld detektieren können. Die Funktionsfähigkeit eines Demonstrators wird mit verschiedenen Flüssigkeiten gezeigt, dabei kommt ein Fotolumineszenz Spektrometer zum Anregen des Evaneszenzfeldes und Auslesen des Signals zum Einsatz. Die entwickelte Integrationsmethode ist eine Basis für ein kostengünstiges, zuverlässiges und reproduzierbares Herstellungsverfahren von optofluidischen Mikrochips basierend auf optisch aktiven Mikroröhrchen.

This work is devoted to investigate light confinement in rolled-up microtubular cavities and their optofluidic applications. The microcavities are fabricated by a roll-up mechanism based on releasing pre-strained silicon-oxide nanomembranes. By defining the shape and thickness of the nanomembranes, the geometrical tube structure is well controlled. Micro-photoluminescence spectroscopy at room temperature is employed to study the optical modes and their dependence on the structural characteristics of the microtubes. Finite-difference-time-domain simulations are performed to elucidate the experimental results. In addition, a theoretical model (based on a wave description) is applied to describe the optical modes in the tubular microcavities, supporting quantitatively and qualitatively the experimental findings. Precise spectral tuning of the optical modes is achieved by two post-fabrication methods. One method employs conformal coating of the tube wall with Al2O3 monolayers by atomic-layer-deposition, which permits a mode tuning over a wide spectral range (larger than one free-spectral-range). An average mode tuning to longer wavelengths of 0.11nm/ Al2O3-monolayer is obtained. The other method consists in asymmetric material deposition onto the tube surface. Besides the possibility of mode tuning, this method permits to detect small shape deformations (at the nanometer scale) of an optical microcavity. Controlled confinement of resonant light is demonstrated by using an asymmetric cone-like microtube, which is fabricated by unevenly rolling-up circular-shaped nanomembranes. Localized three-dimensional optical modes are obtained due to an axial confinement mechanism that is defined by the variation of the tube radius and wall windings along the tube axis. Optofluidic functions of the rolled-up microtubes are explored by immersing the tubes or filling their core with a liquid medium. Refractive index sensing of liquids is demonstrated by correlating spectral shift of the optical modes when a liquid interacts with the resonant light of the microtube. In addition, a novel sensing methodology is proposed by monitoring axial mode spacing changes. Lab-on-a-chip methods are employed to fabricate an optofluidic chip device, allowing a high degree of liquid handling. A maximum sensitivity of 880 nm/refractive-index-unit is achieved. The developed optofluidic sensors show high potential for lab-on-a-chip applications, such as real-time bio/chemical analytic systems.

Vertically rolled-up microcavities are fabricated using differentially strained nanomembranes by employing rate and temperature gradients during electron beam evaporation of SiO2. The geometry of the rolled-up tubes is defined by a photo-lithographically patterned polymer sacrificial layer beneath the SiO2 layers that is dissolved to start the rolling. Rolled-up tubes support resonances formed by constructive interference of light propagating along the circumference. Optical studies are performed in the visible spectral range using a micro-photoluminescence (µPL) setup to excite and detect optical modes. Record high quality factors (Q factors) of 5400 for rolled-up resonators probed in PL-emission mode are found and their limits are theoretically investigated. Axial modes can also be supported when an increased winding number in the center is realized by appropriate pattern designs. In addition, higher order radial modes can be confined when atomic layer deposition (ALD) coatings are applied. Both types of modes are identified using polarization and spatially resolved µPL maps. Evanescent-wave coupling by tapered fibers and tubes on substrates is the second method used to study light confinement and to demonstrate frequency filtering in ALD coated rolled-up microcavities. Scans are performed by monitoring light from a tunable laser in the range of 1520-1570 nm after transmission through the tapered fiber. Dips in the spectrum are found and attributed to fundamental and axial resonant modes. Moreover, by coupling two tapered fibers to a lifted rolled-up microcavity, a four-port add-drop filter is demonstrated as a future component for vertical resonant light transfer in on-chip optical networks. Simulations show that the subwavelength tube wall thickness limits the Q factor at infrared wavelengths and ALD coatings are necessary to enhance the light confinement. After coating, two linear polarization states are found in experiment and fundamental and axial modes can be selectively excited by coupling the fiber to different positions along the tube axis. Spatially and polarization resolved transmission maps reveal a polarization dependent axial mode distribution which is verified theoretically. The results of this thesis are important for lab-on-chip applications where rolled-up microcavities are employed as high resolution optofluidic sensors as well as for future uses as waveguide coupled components in three-dimensional multi-level optical data processing units to provide resonant interlayer signal transfer.

Die Arbeit dient der numerischen Simulation der Spurbildung in Asphaltstraßen und der Herstellung widerstandsfähiger Asphaltmischungen. Zur Modellbildung musste die physikalisch-mechanische Ursache der bleibenden Verformungen bei hohen Temperaturen geklärt werden. Im Gegensatz zu bisher existierenden Stoffmodellen ist in dieser Arbeit das Verhalten teilgesättigter granulerer Stoffe unter zyklischer Belastung als die Grundlage der Untersuchung gewählt worden. Diese zeigen bei entsprechend hoher Sättigung der Hohlräume des mineralischen Korngerüsts unter zyklischer Scherbeanspruchung und bei gleichzeitigem Druck das Phänomen der „zyklischen Mobilität”. Die Erklärung dafür ist die Verdichtungsneigung des Korngerüstes und die Inkompressibilität des Porenfluids, wodurch Porenüberdrücke entstehen. Zyklische Mobilität bedeutet den Abfall der Steifigkeit. Durch die Zunahme der Dehnungsamplituden infolge zyklischer Scherbelastung und der Irreversibilität des granularen Materials verursacht dieses Verhalten die erhöhte Spurbildungsneigung. Die richtige Modellwahl konnte durch systematische experimentelle Ergebnisse belegt werden. Die monotonen triaxialen Kompressionsversuche beweisen die Barotropie und Pyknotropie der Steifigkeit, der Festigkeit und der Dilatanz des mineralischen Korngerüstes. Durch Kompression unter zyklischem Scheren wird die Existenz eines optimalen Bitumengehalts bewiesen, bei welchem die höchste Dichte des Kornegerüstes erreicht werden kann. Bei Mischungen über dem optimalen Bindemittelgehalt wird der Porenfluidüberdruck durch Druckmessungen im Mörtel nachgewiesen. Für den Strassenbauasphalt ist erstmalig zur numerischen Simulation das aus Karlsruhe stammende, mit der „intergranularen Dehnung” erweiterte hypoplastische Stoffgesetz herangezogen worden. Den Schwerpunkt der Arbeit bildet die Bestimmung der hypoplastischen Stoffparameter und die Überprüfung des gewählten Stoffgesetzes durch Nachrechnung von zyklischen Einfachscherversuchen und Triaxialversuchen. In einer selbstentwickelten Torsionszelle wird durch unmittelbare Messung gezeigt, dass der Bitumengehalt über dem Optimum die Schubsteifigkeit verringert. Die Triaxialversuche beweisen die Möglichkeit des Eintretens der zyklischen Mobilität und dadurch die extreme Neigung zur Spurbildung. Diese Messungen beweisen die praktische Bedeutung des optimalen Bitumengehaltes. Das positive Ergebnis der Überprüfung des genanntes Stoffgesetzes liefert die theoretische Unterstützung der experimentellen Ergebnisse. Diese können als Grundlage einer neuen Perspektive in der rechnerischen Prognose sowie beim Entwurf und bei der Herstellung von Asphaltmischungen dienen.

By implementing the rolled-up microfabrication method based on strain engineering, several systems are investigated within the contents of this thesis. The structural morphing of planar geometries into three-dimensional structures opens up many doors for the creation of unique material configurations and devices. An exploration into several novel microsystems, encompassing various scientific subjects, is made and methods for on-chip integration of these devices are presented. The roll-up of a metal and oxide allows for a cylindrical hollow-core structure with a cladding layer composed of a multilayer stack, plasmonic metamaterial. This structure can be used as a platform for a number of optical metamaterial devices. By guiding light radially through this structure, a theoretical investigation into the system makeup of a rolled-up hyperlens, is given. Using the same design, but rather propagating light parallel to the cylinder, a novel device known as a metamaterial optical fiber is defined. This fiber allows light to be guided classically and plasmonically within a single device. These fibers are developed experimentally and are integrated into preexisting on-chip structures and characterized. A system known as lab-in-a-tube is introduced. The idea of lab-in-a-tube combines various rolled-up components into a single all-encompassing biosensor that can be used to detect and monitor single bio-organisms. The first device specifically tailored to this system is developed, flexible split-wall microtube resonator sensors. A method for the capturing of embryonic mouse cells into on-chip optical resonators is introduced. The sensor can optically detect, via photoluminescence, living cells confined within the resonator through the compression and expansion of a nanogap built within its walls. The rolled-up fabrication method is not limited to the well-investigated systems based on the roll-up from semiconductor material or from a photoresist layer. A new approach, relying on the delamination of polymers, is presented. This offers never-before-realized microscale structures and configurations. This includes novel magnetic configurations and flexible fluidic sensors which can be designed for on-chip and roving detector applications.

Plastic deformation of metals and alloys are invariably accompanied by the development of texture. The origin of texture is attributed to the deformation micro-mechanisms associated with processing. The face-centered cubic (FCC) metals and alloys are known to exhibit two distinct types of textures when subjected to large strain rolling deformation, namely, (i) Cu-type texture, commonly seen in high/medium stacking fault energy (SFE) materials, (ii) Bs-type texture in low SFE materials. The circumstances that could result in the formation of Bs-type texture in low SFE materials still remains an open question and no definite mechanism has been uniquely agreed upon. Apart from the SFE, grain size could also influence the deformation mechanism and hence the deformation texture. It is well known that in materials with grain sizes less than 100 nm (referred to as nano-crystalline materials), the microstructures contain large fraction of grain boundaries. This subsequently introduces a variety of deformation mechanisms in the microstructure involving grain boundary-mediated processes such as grain boundary sliding and grain rotation, in addition to slip and twinning. A clear understanding of texture evolution in nano-crystalline materials, particularly at large strains, is a topic that remains largely unexplored. The present work is an attempt to address the aforementioned issues pertaining to the evolution of deformation texture, namely, (i) the effect of SFE and (ii) the effect of grain size, in FCC metals and alloys. Nickel-cobalt alloys are chosen as the model system for the present investigation. The addition of cobalt to nickel leads to a systematic reduction of SFE as a function of cobalt content. In this thesis, three alloys of Ni-Co system have been considered, namely, nickel – 20 wt.% cobalt, nickel – 40 wt.% cobalt and nickel – 60 wt.% cobalt. For a comparison, pure nickel has also been subjected to similar study. Chapter 1 of the thesis presents a detailed survey of literature pertaining to the evolution of rolling textures in FCC metals and alloys, and chapter 2 includes the details of the experimental techniques and characterization procedures, which are commonly employed for the entire work. Chapter 3 addresses the effect of stacking fault energy on the evolution of rolling texture. The materials subjected to study in this chapter are microcrystalline Ni-Co alloys. The texture evolution in Ni-20Co is very similar to pure Ni, and a characteristic Cu-type rolling texture is observed. The evolution of texture in these materials is primarily attributed to the intense dislocation activity throughout the deformation stages. In Ni-40Co, a medium SFE material, the rolling texture was predominantly Cu-type up to a strain of ε = 3 (95% thickness reduction). However, beyond this strain level, namely at ε = 4 (98%), the texture gets transformed to Bs-type with orientations maxima predominantly close to Goss ({110} <001>) position. Simultaneously, the Cu component which was dominant until 95% reduction has completely disappeared. The analysis of microstructures indicate that deformation is mostly accommodated by dislocation slip up to 95%, however, at ε > 3, Cu-type shear bands get initiated, preferably in the Cu-oriented ({112} <111>) grains. The sub-grains within the shear bands show preferred orientation towards Goss, which indicates that the Cu component should have undergone transformation and resulted in high fraction of Goss component. In Ni-60Co alloy, Bs-type texture forms in the early stages of deformation (ε ~ 0.5) itself and further deformation results in strengthening of the texture with an important difference that the maximum in orientation distribution has been observed at a location close to Goss component, rather than at exact Bs-location. The development of Bs-type texture is accompanied by the complete absence of Cu and S components. Extensive EBSD analyses show that the deformation twinning gets initiated beyond 10% reduction and was found extensively in most of the grains up to 50% reduction. At higher strains, tendency for twinning ceases and extensive shear banding is observed. A non-random distribution of orientations close to Goss orientation was found within the shear bands. The near-Goss component in the Ni-60Co alloy can be explained on the basis of deformation twinning and shear banding. Thus, a reasonable understanding of the deformation texture transition in the extreme SFE range has been developed. In chapter 4, the effect of fine grain size on the evolution of rolling texture has been addressed. Nanocrystalline (nc) nickel-cobalt alloys with a mean grain size of ~20 nm have been prepared by pulse electro-deposition method. For a comparison, nc Nickel (without cobalt) with similar grain size has also been deposited. For all the materials, a weakening of the initial fiber texture is observed in the early stage of room temperature rolling (ε ~ 0.22). A combination of equiaxed grain microstructure and texture weakening suggests grain boundary sliding as an operative mechanism in the early stage of rolling. At large strain (ε = 1.2), Ni-20Co develops a Cu-type texture with high fractions of S and Cu components, similar to pure Ni. The texture evolution in Ni-40Co and Ni-60Co alloys is more towards Bs-type. However, the texture maximum occurs at a location 10° away from the Goss. The evolution of Cu and S components in nc Ni-60Co alloy takes place simultaneously along with the α-fiber components during rolling. Microstructural investigation by TEM indicates deformation twinning to be more active in all the materials up to 40% reduction. However, no correlation could be drawn between the texture evolution and the density of twins. The deformation of nc Ni-20Co alloy, is also accompanied by significant grain growth at all the stages of rolling. The increase in grain size, subsequently, renders the texture to be of Cu-type. However, Ni-40Co and Ni-60Co alloys show high grain stability. The absence of strain heterogeneities such as shear bands, and the lack of significant fraction of deformation twins indicate that the observed Bs-type texture could be due to planar slip. The increase in deformation beyond 70% reduction caused a modest reduction in the intensity of deformation texture. The microstructural observation indicates the occurrence of restoration mechanisms such as recovery/ recrystallization at large strains. The overall findings of the investigation have been summarized in chapter 5. The deformation mechanism maps relating stacking fault energy with amount of strain and with grain size are proposed for micro- and nano- crystalline materials respectively.