Non-fullerene Acceptors (NFAs) have gathered a great deal of interest for use inorganic photovoltaics (OPVs) due to recent breakthroughs in their power conversion efficiency and other advantages they offer over their Fullerene-based counterparts. In this work, a new promising non-fullerene polymer acceptor, PF5-Y5, have been studied using density functional theory and time-dependent density functional theory; and the effects that oligomer length, geometry relaxation and exchange-correlation interaction has on the exciton binding energies (the difference between optical and fundamental energy gaps) have been investigated. Both the fundamental and optical gaps are significantly affected by the choice of functional (i.e., the description of the exchange-correlation interaction). However, it does not appear to significantly impact obtained exciton binding energies as the effects of the fundamental and optical gaps cancel each other out. Both the fundamental and optical energy gap are shown to slightly reduce as a function of the oligomer length (~0.1 - 0.3 𝑒𝑉 reduction for each repeated monomer). As both gaps are reduced by a similar amount per repeated monomer, they counteract each other and the total effect that oligomer length has on the exciton binding energy is very low. Geometry relaxation and thermal effects showed the largest impact on the fundamental gap and exciton binding energy, with their combined effect resulting in a ~0.5 𝑒𝑉 reduction in binding energy. / Non-Fullerene Acceptorer (NFAs) har rönt stort intresse för användning i organiska solceller (OPVs) på grund av genombrott på senare tid gällande deras effektomvandlingsverkningsgrad och en mängd andra fördelar som de erbjuder jämfört med sina fullerene-baserade motsvarigheter. I det här arbetet har en ny lovande polymer-acceptor, PF5-Y5, studerats med hjälp av täthetsfunktionalteori (DFT) och tidsberoende täthetsfunktionsteori (TD-DFT). Effekterna som oligomerlängd, geometri-avslappning och utbytes-korrelations-interaktion har på exciton-bindningsenergin (skillnaden mellan optiska ochfundamentala energigapen) har även undersökts.  Både erhållna värden för det fundamentala och optiska gapet påverkas avsevärt av valet av funktional (dvs. beskrivningen av utbytes-korrelations-interaktionen). Valet av funktional verkar dock inte nämnvärt påverka erhållna värden för excitonbindningsenergin då effekterna från det fundamentala och optiska gapen till stor del tar ut varandra.  Både det fundamentala och optiska energigapet minskar som en funktion av oligomerlängden (~0.1 - 0.3 𝑒𝑉 minskning för varje upprepad monomer). Eftersom båda energigapen minskar ungefär lika mycket för varje upprepad monomer så motverkar de till stor grad varandra; och den totala effekten som oligomerlängd har på exciton-bindningsenergin förblir låg. Strukturell relaxation (eng: geometry relaxation) och termiska effekter visade sig ha störst påverkan på det fundamentala energigapet och exciton-bindningsenergin, och deras sammanlagda effekt ledde till en ~0,5 𝑒𝑉 reduktion i bindningsenergi.

Industrial innovation is mostly driven by miniaturization. As a result of remarkable technological advancements in the fields of equipment, materials and production processes, transistor, the fundamental active component in conventional electronics, has shrunk in size. Semiconductor technology is unique in that all performance metrics are enhanced, while at the same time unit prices are reduced. Moore’s Law, which predicts that the number of components per chip will double every two years, was established in 1965, and the industry has been able to keep up with this prophetic prognosis since. Thermal management, on the other hand, has become a key limiting factor for current electronic circuits and is set to put a stop to Moore’s Law. Given the fact that complementary metal oxide semiconductor (CMOS) scaling is reaching fundamental limits, there are several new alternative processing devices and architectures that have been investigated for both traditional integrated circuit (IC) technologies and novel technologies, including new technologies aimed at contributing to advances in scaling progress and cost reductions in manufacturing operations in the coming decades. These factors will encourage the development of new information processing and memory systems, new technologies for integrating numerous features heterogeneously and new system architectural design layouts, among other things. Energy efficiency is advantageous from a sustainability perspective and for consumer electronics, for which fewer power-hungry components mean longer times between charges and smaller batteries. The creation of novel chip-scale tools that can aid in the transfer of information across optical frequencies and microscale photonics between nanoscale electronic devices is now a possibility. Bridging this technological gap may be achieved by plasmonics. The incorporation of plasmonic, photonic and electrical components on a single chip may lead to a number of innovative breakthroughs. Photonic integrated circuits (PICs) enable the realization of ultra-small, high-efficiency, ultra-responsive and CMOS-compatible devices that can be used in applications ranging from optical wireless communication systems (6G and beyond) and supercomputers to health and energy.   This thesis provides a platform from which to design nanoplasmonic devices while facilitating high-transmission and/or absorption efficiency, miniaturized size and the use of near-infrared (NIR) wavelengths for telecom applications. With a significant amount of Internet traffic transmitted optically, communication systems are further tightening the requirements for the development of new optical devices. Several new device structures based on the metal-insulator-metal (MIM) plasmonic waveguide are proposed and investigated using performance metrics. The transmission line theory (TLM) from microwave circuit theory and coupled mode theory (CMT) is studied and employed in the design process of the nanostructures, in particular to address the losses in plasmonic-based devices, which has been the major factor hampering their widespread usage in communication systems. By taking advantage of well-established microwave circuit theory (through new design that paves the way for mitigating these losses and enabling efficient transmission of power flow in the optical devices), we have suggested a number of high-transmission efficiency nanodevices that offer highly competitive performance compared with other platforms. As a result, a promising future for plasmonic technology, which would enable design and fabrication of multipurpose and multifunctional optical devices that are efficient in terms of losses, footprint and capability of integrating active devices, is anticipated. / Branschinnovation drivs främst av miniatyrisering. Som ett resultat av anmärkningsvärda tekniska framsteg inom områdena utrustning, material och produktionsprocesser kunde transistoren, den grundläggande aktiva komponenten i samtida elektronik, krympa i storlek. Halvledarteknik är unik genom att alla prestandamått förbättras, samtidigt som enhetspriserna sänks. Moores Lag, som förutspår att antalet komponenter per chip skulle fördubblas vartannat år, inrättades 1965, och branschen har kunnat hålla jämna steg med den profetiska prognosen sedan dess. Termisk hantering, å andra sidan, har blivit en viktig begränsande faktor för nuvarande elektroniska kretsar, och är inställd på att sätta stopp för Moores Lag. Med tanke på att CMOS-skalningen (Complementary Metal Oxide Semiconductor) når grundläggande gränser finns det flera nya alternativa bearbetningsanordningar och arkitekturer som har undersökts för både traditionell integrerad kretsteknik och ny teknik. Ny teknik som syftar till att bidra till framsteg i skalningen av framsteg och kostnadsminskningar i tillverkningsverksamheten under de kommande årtiondena. Dessa faktorer uppmuntrar utvecklingen av nya informationsbehandlings- och minnessystem, ny teknik för att integrera många funktioner heterogent och nya systemarkitekturdesignlayouter, bland annat. Energieffektivitet är fördelaktigt ur ett hållbarhetsperspektiv och för hemelektronik, där färre krafthungriga elektroniker innebär längre tid mellan laddningar och stimulerar för ett mindre energilagringssystem ombord. Skapandet av nya chip-scale verktyg som kan bidra till överföring av information över optiska frekvenser och mikroskala fotonik mellan elektroniska enheter i nanoskala är nu en möjlighet. Överbrygga denna tekniska klyfta kan uppnås av plasmonics. Införlivandet av plasmoniska, fotoniska och elektriska komponenter på ett enda chip kan leda till ett antal innovativa genombrott. Fotoniska integrerade kretsar (PIC-enheter) möjliggör förverkligande av ultrasmå, högeffektiva, ultraresponsiva och CMOS-kompatibla enheter som kan användas i applikationer som sträcker sig från optiska trådlösa kommunikationssystem (6G och därefter), superdatorer till hälso- och energiändamål. Denna avhandling ger en plattform för att designa nanoplasmoniska enheter samtidigt som den innehåller hög överförings- och eller absorptionseffektivitet, miniatyriserad storlek och vid önskade våglängder av nära infraröd (NIR) för telekomapplikationer. Med den betydande mängden Internettrafik som överförs optiskt skärper kommunikationssystemen ytterligare kraven för utveckling av nya optiska enheter. Flera nya enhetsstrukturer baserade på metall-isolator-metall (MIM) plasmonisk vågledare föreslås och numeriskt undersöks. Överföringslinjeteorin (TLM) från mikrovågskretsteori och kombinationslägesteori (CMT) studeras och används i nanostrukturerna. För att ta itu med de förluster i plasmonbaserade enheter som har varit den viktigaste parametern som hindrade deras utbredda användning i kommunikationssystem, genom att dra nytta av den väletablerade mikrovågskretsteorin (genom ny design som banar väg för att mildra förlusterna och möjliggöra effektiv överföring av kraftflödet i den optiska enheten).  Vi har framgångsrikt föreslagit ett antal nanodevices med hög överföringseffektivitet som erbjuder en mycket konkurrenskraftig prestanda jämfört med andra plattformar. Som ett resultat förväntar vi oss en lovande framtid för plasmonisk teknik som skulle möjliggöra design och tillverkning av mångsidiga och multifunktionella optiska enheter som är effektiva när det gäller förluster, fotavtryck och förmåga att integrera aktiva enheter. / <p>Vid tidpunkten för framläggandet av avhandlingen var följande delarbeten opublicerade: delarbete II inskickat, III, IV, V manuskript.</p><p>At the time of the licentiate defence the following papers were unpublished: paper II submitted, III, IV, V manuscript.</p>

Over the past 20 years’ researchers have tried to utilize the remarkable properties of single-walled carbon nanotubes (SWCNTs) to create new high-tech materials and devices, such as strong light-weight composites, efficient electrical wires and super-fast transistors. But the mass production of these materials and devices are still hampered by the poor uniformity of the produced SWCNTs. These are hollow cylindrical tubes of carbon where the atomic structure of the tube wall consists of just a single atomic layer of carbon atoms arranged in a hexagonal grid. For a SWCNT the orientation of the hexagonal grid making up the tube wall is what determines its properties, this orientation is known as the chirality of a SWCNT. As an example, tubes with certain chiralities will be electrically conductive while others having different chiralities will be semiconducting. Today’s large scale methods for producing SWCNTs, commonly known as growth of SWCNTs, gives products with a large spread of different chiralities. A mixture of chiralities will give products with a mixture of different properties. This is one of the major problems holding back the use of SWCNTs in future materials and devices. The ultimate goal is to achieve growth where the resulting product is uniform, meaning that all of the SWCNTs have the same chirality, a process termed chirality-specific growth. To achieve chirality-specific growth of SWCNTs requires us to obtain a better fundamental understanding about how they grow, both from an experimental and a theoretical point of view. This work focuses on theoretical studies of SWCNT properties and how they relate to the growth process, thereby giving us vital new information about how SWCNTs grow and taking us ever closer to achieving the ultimate goal of chirality-specific growth. In this thesis, an introduction to the field is given and the current state of the art experiments focusing on chirality-specific growth of SWCNTs are presented. A brief review of the current theoretical works and computer simulations related to growth of SWCNTs is also presented. The results presented in this thesis are obtained using first principle density functional theory. The first study shows a correlation between the stability of SWCNT-fragments and the observed products from experiments. Calculations confirm that in 84% of the investigated cases the chirality of experimental products matches the chirality of the most stable SWCNT-fragments (within 0.2 eV). Further theoretical calculations also reveal a previously unknown link between the stability of SWCNT-fragments and their length. The calculations show that at specific SWCNT-fragment lengths the most stable chirality changes. Thus, introducing the concept of a switching length for SWCNT stability. How these new results link to the existing understanding of SWCNT growth is discussed at the end of the thesis.

The aim of this project is to examine the electric and magneticproperties of three monolayer chromium trihalides when doped withdifferent transitions metals, that is CrXY_6, where X=(Mn,Fe,Co,Ni,V)and Y=(Cl,Br,I). The calculations were made using the software programQuantum Espresso that used density functional theory to solveSchrödinger’s equation. The first step of the calculations was to optimize the atomic positionsand the lattice parameters to find the ground state energy of thecompounds. The magnetic configuration was also examined to find thefavorable configuration. With the optimized values for each compound,the band structure, density of states and the projected density ofstates was calculated. The results confirmed the ferromagnetic behaviorof non-doped compounds, however for some of the doped compounds themagnetic configurations changed to anti-ferromagnetic. Most of thecompounds retained their semiconductor properties when doped and had aband gap near the fermi-energy, while other changed to metallic or halfmetallic and had available electron states at fermi-energy.

Ultra-thin solar cells that incorporate earth-abundant and non-toxic materials are promising candidates in the endeavor toward sustainable energy harvesting. Methods to counteract the inevitable low absorption of thinner semiconductor layers are of high interest and have raised considerable attention in the research society. In an attempt to increase the absorption of these types of assemblies, optical coupling effects between the localized surface plasmon resonances (LSPR) of disordered Au nanostructures and a Fabry-Pérot cavity were studied using a previously established absorber/spacer/reflector stack. The disordered Au array was fabricated by evaporating a thin Au film on a substrate with a 55 nm SiO2 dielectric spacer and a 100 nm Al reflecting film, followed by thermal annealing. Nominal Au film thicknesses in the range of 5-25 Å and annealing temperatures of 200-500 oC were investigated. In situ spectroscopic ellipsometry measurements during the subsequent atomic layer deposition (ALD) of tin monosulfide (SnS) allowed analysis of how the optical properties of the SnS/Au absorber layer changed as a function of the growing SnS layer thickness. By employing the Transfer Matrix Method with the estimated optical properties from the in situ analysis, the absorptance of the absorber/spacer/reflector stacks was simulated as a function of the spacer thickness, revealing any signs of the characteristic anti-crossing behavior. It was discovered that a nominal Au film thickness of 25 Å, annealed at 450 oC, and coated with a SnS film of ∼13 nm primed toward the π-phase, resulted in strong optical coupling between the cavity mode and the LSPR. The energy difference at the avoided crossing in the specular reflectance measurement gave an estimated Rabi-splitting energy of 537 meV. This corresponded to about 40% of the original LSPR energy, placing itself within the ultra-strong coupling regime. To evaluate the relevance of the thin-layered structure in photovoltaic applications, more advanced computational methods are required to estimate the useful absorption that occurs in the SnS layer. Nevertheless, these results elucidate the realization of strong optical coupling effects between disordered Au nanostructures and a Fabry-Pérot cavity, and further the possibility of using scalable fabrication methods for this type of ultra-thin absorber/spacer/reflector stack.

No description available.

To increase the survival rate from infectious- and noncommunicable diseases, reliable diagnostic during the preliminary stages of a disease onset is of vital importance. This is not trivial to achieve, a highly sensitive and selective detection system is needed for measuring the low concentrations of biomarkers available. One possible route to achieve this is through biosensing based on plasmonic nanostructures, which during the last decade have demonstrated impressive diagnostic capabilities. These nanoplasmonic surfaces have the ability to significantly enhance fluorescence- and Raman signals through localized hotspots, where a stronger then normal electric field is present. By further utilizing a periodic sub-wavelength nanohole array the extraordinary optical transmission phenomena is supported, which open up new ways for miniaturization. In this study a nanoplasmonic chip (NPC) composed of a nanohole array —with lateral size on the order of hundreds of nanometer— covered in a thin layer of gold is created. The nanohole array is fabricated using soft nanoimprint lithography on two resists, hydroxypropyl cellulose (HPC) and polymethyl methacrylate (PMMA). An in depth analysis of the effect of thickness is done, where the transmittance and Raman scattering (using rhodamine 6G) are measured for varying gold layers from 5 to 21 nm. The thickness was proved to be of great importance for optimizing the Raman enhancement, where a maximum was found at 13 nm. The nanohole array were also in general found beneficial for additionally enhancing the Raman signal. A transmittance minima and maxima were found in the region 200-1000 nm for the NPCs, where the minima redshifted as the thickness increased. The extraordinary transmission phenomena was however not observed at these thin gold layers. Oxygen plasma treatment further proved an effective treatment method to reduce the hydrophobic properties of the NPCs. Care needs be taken when using thin layers of gold with a PMMA base, as the PMMA structure could get severely damaged by the plasma. HPC also proved inadequate for this projects purpose, as water-based fluids easily damaged the surface despite a deposited gold layer on top.

The wall thickness of pulp fibers plays a major role in the paper industry, but it is currently not possible to measure this property without manual laboratory work. In 2007, researcher Ho Fan Jang patented a technique to automatically measure fiber wall thickness, combining the unique optical properties of pulp fibers with image analysis. In short, the method creates images through the use of an optical system resulting in color values which demonstrate the retardation of a particular wave length instead of the intensity. A device based on this patent has since been developed by Eurocon Analyzer. This thesis investigates the software aspects of this technique, using sample images generated by the Eurocon Analyzer prototype. The software developed in this thesis has been subdivided into three groups for independent consideration. First being the problem of solving wall thickness for colors in the images. Secondly, the image analysis process of identifying fibers and good points for measuring them. Lastly, it is investigated how statistical analysis can be applied to improve results and derive other useful properties such as fiber coarseness. With the use of this technique there are several problems which need to be overcome. One such problem is that it may be difficult to disambiguate the colors produced by fibers of different thickness. This complication may be reduced by using image analysis and statistical analysis. Another challenge can be that theoretical values often differ greatly from the observed values which makes the computational aspect of the method problematic. The results of this thesis show that the effects of these problems can be greatly reduced and that the method offers promising results. The results clearly distinguish between and show the expected characteristics of different pulp samples, but more qualitative reference measurements are needed in order to draw conclusions on the correctness of the results.

In a time when microorganisms are controlling the world, research in biology is more relevant than ever and this requires some powerful instruments. Optical tweezers use a focused laser beam to manipulate and probe objects on the nano- and microscale. This allows for the exploration of a miniature world at the border between biology, chemistry and physics. New methods for biophysical and physicochemical measurements are continuously being developed and at Umeå University there is a need for a new system that combines several of these methods. This would truly be the new Swiss army knife of biophysical and biomechanical research, extending their reach in the world of optical tweezing. My ambition with this project is to design and construct a robust system that incorporates optical trapping with high-precision force measurements and Raman spectroscopy, as well as introducing the possibility of generating multiple traps by using a spatial light modulator (SLM). The proposed design incorporates four different lasers and a novel combination of signal detection techniques. To allow for precise control of the systems components and laser beams, I designed and constructed motorized opto-mechanical components. These are controlled by an in-house developed software that handles data processing and signal analysis, while also providing a user interface for the system. The components include, motorized beam blockers and optical attenuators, which were developed using commonly available 3D printing techniques and electronic controllers. By designing the system from scratch, I could eliminate the known weaknesses of conventional systems and allow for a modular design where components can be added easily. The system is divided into two parts, a laser breadboard and a main breadboard. The former contains all the equipment needed to generate and control the laser beams, which are then coupled through optical fibers to the latter. This contains the components needed to move the optical trap inside the sample chamber, while performing measurements and providing user feedback. Construction and testing was done for one sub-system at a time, while the lack of time required a postponement for the implementation of Raman and SLM. The system performance was verified through Allan variance stability tests and the results were compared with other optical tweezers setups. The results show that the system follows the thermal limit for averaging times (τ) up to ~1 s when disturbances had been eliminated, which is similar to other systems. However, we could also show a decrease in variance all the way to τ = 2000 s, which is exceptionally good and not found in conventional systems. The force-resolution was determined to be on the order of femtonewtons, which is also exceptionally good. Thus, I conclude that this optical tweezers setup could lie as a solid foundation for future development and research in biological science at Umeå University for years to come.

Hard chrome exhibit hardness of about 70 HRC and lubricity that prevents seizing and galling and is therefore the common first choice for engineers to reduce friction and minimize wear. These properties enable engineering applications such as cutting and drilling, especially in manufacturing, production and consumer good industries. Hard chrome has a wide set of functions as being decorative, corrosion resistant and ease cleaning procedures. Hence, electroplating is a common process to synthesize hard chrome butthis process is banned by EU due to the rise of hazardous components. However, the need for alternative material is at rise but, fundamental issues for hard chrome are yet to be solved. The purpose of the work is to develop atomic structures for two systems using different programs such as OpenMX, VESTA and Ovito. The goal is to identify atomic wear mechanisms of hard chrome in an ideal system (Al2O3- Cr) and a real system (Al2O3 - Cr2O3) using density functional theory (DFT). These two systems are analyzed since every surface oxidises in air (real system) and under increased mechanical loads the pristine surface of hard chrome (ideal system) can be exposed to the counter body (Al2O3). DFT based molecular dynamics simulations are carried out at a temperature of 300 K and a sliding speed of 10 ms−1. The simulation interval is 0-15000 fs and radial distribution function (RDF) is employed to analyse the atomic wear mechanisms. Both systems start to show adhesive wear due to amorphization, mixed with signs of abrasive wear on the atomic scale. The systems are further analyzed using electron density distribution (EDD), that plots electronic structures enhancing the analyse of different type of bondstaking place. The bulk structures mainly show covalent bonds with ionic and metallic bonds less represented. Furthermore, same observations have been made for the interfaces of the ideal and real system. / Hårdkrom uppvisar hårdhet på ungefär 70 HRC och en smörjförmåga som förhindrar nötning och är därför det vanliga första valet för ingenjörer att minska friktionen och minimera slitaget. Dessa egenskaper möjliggör tekniska tillämpningar, såsom skärning och borrning, särskilt inom tillverknings, produktions och konsumentvaruindustrin. Hårdkrom har ett brett användningsområde och flera egenskaper såsom att vara dekorativ, korrosionsbeständig och underlätta rengöringsprocedurer. Därav är galvanisering en vanlig process för att syntetisera hårdkrom, men denna process är förbjuden av EU på grund av utsläpp av farliga komponenter. Behovet av alternativt material är vid uppgång men, de grundläggande problemen för hård krom är ännu inte lösta. Syftet med arbetet är att ta fram atom strukturer för två system med hjälp av olika program, såsom OpenMX, VESTA och Ovito. Målet är att identifiera vilken typ av nötning som sker på hårdkrom i ett idealt system (Al2O3- Cr) och i ett verkligt system (Al2O3- Cr2O3) genom att använda täthetsfunktionalteorin (DFT). Dessa två system analyseras eftersom varje yta oxiderar i luften (verkligt system) och under ökade mekaniska belastningar kan den orörda ytan av hårtkrom (idealiskt system) exponeras för motkroppen (Al2O3). DFT simuleringar är skapade med en temperatur på 300 K och en glidningshastighet på 10 ms−1. Simulerings intervallet är från 0-15000 fs och med hjälp av radiell fördelningsfunktion (RDF) analyseras de atomiska nötnings mekanismerna. Båda systemen börjar visa adhesiv nötning på grund av amorfisering, samt ett tecken på abrasiv nötning på en atomisk skala. Systemen analyseras vidare med användning av elektrondensitetsfördelning (EDD) som plottar elektroniska strukturer vilket förbättrar analysen av olika typer av bindningar som äger rum. Bulkstrukturerna visar huvudsaklig en kovalent bindning med joniska och metalliska bindningar mindre representerade. Samma observationer har gjorts för gränssnitten mellan det ideala och verkliga systemet.