Magnetic data storing has been of great interest since 1950 when the first magnetic hard drive was fabricated. A lot has happened since then, but there is still a need for smaller and cheaper devices.  One way to achieve this is by creating nano-sized ferromagnetic areas in a thin film at room temperature, or nano-magnets. In this thesis, the aim is to fabricate and characterize novel amorphous nano-magnets. Using a chromium mask ions can be implanted in a nano-sized pattern in an amorphous iron zirconium thin film. The mask is fabricated by depositing chromium over the iron zirconium and etching the nano-structures into the chromium film.  This requires the parameters for the etching to be optimized. It is discovered the parameters change with the size and shape of the pattern. Magnetization and structural characterization were performed by using the magneto-optical Kerr effect and a magnetic force microscope. The result shows that the nano-magnets become magnetically harder than the reference sample. The study further reveals structural details for further improvements in implanted regions. / <p>Opponent: Stivan Sabir</p>

Carbon dioxide is an important gas for life on Earth. But as human activities have been expanding throughout modern history, the CO2 concentration in the atmosphere is increasing. High concentrations of carbon dioxide can lead to various consequences, such as climate change and poor air quality both indoors and outdoors. It is therefore of importance to detect this gas, in order to understand our environment, and to avoid health impacts that it may cause. Non-dispersive infrared sensors are widely used in CO2 sensing and are based on optical absorption technology. This thesis investigates the optical performance of suspended waveguides for non-dispersive infrared sensors, with regard to different material qualities, i.e. monocrystalline and polycrystalline silicon, and geometries of these waveguides. The waveguides that are studied in this thesis consist of splitters, and at the end of each splitter a grating coupler that projects the IR radiation perpendicularly from the plane of the chip. Measurements are conducted to evaluate the IR radiation propagation loss of the waveguides and their feasibility for sensing carbon dioxide. It has been found that longer waveguides suffer from high propagation losses. When comparing the polycrystalline silicon with monocrystalline silicon waveguides, it has been observed in the measurements that the IR radiation propagates better in monocrystalline silicon waveguides than in polycrystalline silicon because of their crystal structures. The measured propagation loss in polycrystalline silicon waveguides is less than the loss obtained for the monocrystalline silicon waveguides, although some intensities from the grating couplers are excluded in the calculations, due to low signal strength. It is also concluded that the studied waveguides are feasible for detecting carbon dioxide with a concentration of 1%. Further investigation regarding the feasibility of gas sensing using lower concentrations of CO2 would be interesting for future work.

In the semiconductor industry, the purification process of the silicon wafers is of a great importance. If water of sufficient quality is not used, the silicon wafer surface runs a risk of being destroyed by particles and bacteria sticking to its surface. Semiconductors cannot be manufactured on the destroyed surfaces and to achieve the highest efficiency of the circuits, water with high purity is required for the purification process. The silicon wafers produced by the manufacturer have an oxide layer on them as a protective layer. This oxide layer needs to be cleaned off before it can be used for the manufacture of semiconductors. The oxide layer is removed by applying 5% hydrogen fluoride (HF) to the surface which is afterwards cleaned away with water. It is mainly within this part of the purification process that particles and bacteria get stuck on the surface of the silicon wafer. At present, water of poor quality is used which is unable to dilute and purify the mixture that becomes with hydrogen fluoride and the oxide layer.   As development is constantly advancing and the line width of the circuits becomes narrower and smaller, water with almost no particles is needed to clean these small areas. The particle size of the water must not exceed 20 nm in order to effectively clean the silicon wafers and preferably the particle size should not exceed 10 nm.   In the present study, an air gap membrane distillation module was investigated for the purpose of verifying the purity of the water where spherical spheres of 20 nm diameter were added into the purified water and examined in a dynamic light scattering (DLS). Because ultrapure water (UPW) is a very aggressive water, storage is a problem. Four different container materials ability to store UPW with maintained purity were studied; white borosilicate glass, brown borosilicate glass, ethylene chlorotrifluoroethylene (ECTFE) and polyvinylidene fluoride (PVDF).   Experiments were also done to further verify the purity of the water by adding ultrapure water on a silicon wafer and allowing it to dry to study the dry spots. The dry spots were studied in an SEM to see if the water left any particles behind on the surface. The same experiment was also done with tap water and distilled water which was dripped on a silicon wafer and dried. These dry spots were examined in a scanning electron microscope (SEM). To investigate how effectively ultrapure water cleans a silicon wafer, an amount of 5% hydrogen fluoride on a silicon wafer was added and rinsed with ultrapure water and tap water respectively. The same experiment was also done with tap water for comparison. These silicon wafers were studied in an SEM to see if any particles were left on its surface from the respective water. An initial methodology was also done when 5% hydrogen fluoride was diluted with ultrapure water and tap water to compare the amount of respective water it used to dilute this acid.   In the present study, simulations were made on the air gap membrane distillation module in COMSOL where four different geometries were simulated with the aim to see how the temperature profile on the hot and cold side changed as the geometry and area of the membranes changed.   The purity of the water produced with the air gap membrane distillation were verified with DLS and the particle size did not exceed 20 nm. Further experiments showed that with UPW, there were no dry spots on the surface of the silicon wafer and no particles could be seen when the silicon wafer was examined in a SEM. When the tap water was dropped on the silicon wafer and dried, one could clearly see the drying spots. When the silicon wafer was examined in an SEM, there were many particles left on the surface. The distilled water left no drying stains on the surface but on the other hand, it was able to see particles on the surface when examined in a SEM. When 5% hydrogen fluoride had been dropped on the surface and washed away with UPW, no particles could be detected when examined in an SEM. However, particles were found when the same amount of hydrogen fluoride was rinsed off with tap water.   When 5% hydrogen fluoride was diluted to a neutral pH of 6-7, about 200 ml of UPW were used as separated from tap water where it went to the quadruple to dilute the same amount of hydrogen fluoride. This showed the purity of the ultrapure water compared to tap water.   For the simulations it was possible to see how the temperature profile changed with the area. With a large area, the temperature profile on the hot and cold side became very poor. The temperature on the hot side dropped a lot and on the cold side it increased a lot. The largest area simulated was 255x255 mm. With a smaller area, a more even temperature profile was obtained. The area that gave the best temperature profile was 180x100 mm, which was the smallest area investigated. In contrast, the diffusion area becomes smaller as the area decreases, leading to a reduced production of ultrapure water.   This study is close to research and is about developing new technology and modifying/improving existing technology.

Indiana University-Purdue University Indianapolis (IUPUI) / Recent ULSI (ultra large scale integration) technology emphasizes small size devices, featuring low power and high switching speed. Moore's law has been followed successfully in scaling down the silicon device in order to enhance the level of integration with high performances until conventional devices failed to cop up with further scaling due to limitations with ballistic effects, and challenges with accommodating dopant fluctuation, mobility degradation, among other device parameters. Recently, Graphene based devices o ered alternative approach, featuring small size and high performances. This includes high carrier mobility, high carrier density, high robustness, and high thermal conductivity. These unique characteristics made the Graphene devices attractive for high speed electronic architectures. In this research, Graphene devices were integrated into applications with analog, digital, and mixed signals based systems. Graphene devices were briefly explored in electronics applications since its first model developed by the University of Illinois, Champaign in 2013. This study emphasizes the validation of the model in various applications with analog, digital, and mixed signals. At the analog level, the model was used for voltage and power amplifiers; classes A, B, and AB. At the digital level, the device model was validated within the universal gates, adders, multipliers, subtractors, multiplexers, demultiplexers, encoders, and comparators. The study was also extended to include Graphene devices for serializers, the digital systems incorporated into the data structure storage. At the mixed signal level, the device model was validated for the DACs/ADCs. In all components, the features of the new devices were emphasized as compared with the existing silicon technology. The system functionality and dynamic performances were also elaborated. The study also covered the linearity characteristics of the devices within full input range operation. GNRFETs with a minimum channel length of 10nm and an input voltage 0.7V were considered in the study. An electronic design platform ADS (Advanced Design Systems) was used in the simulations. The power amplifiers showed noise figure as low as 0.064dbs for class A, and 0.32 dbs for class B, and 0.69 dbs for class AB power amplifiers. The design was stable and as high as 5.12 for class A, 1.02 for class B, and 1.014 for class AB. The stability factor was estimated at 2GHz operation. The harmonics were as low as -100 dbs for class A, -60 dbs for class B, and -50dbs for class AB, all simulated at 1GHz. The device was incorporated into ADC system, and as low as 24.5 micro Watt power consumption and 40 nsec rise time were observed. Likewise, the DAC showed low power consumption as of 4.51 micro Watt. The serializer showed as minimum power consumption of the order of 0.4mW. These results showed that these nanoscale devices have potential future for high-speed communication systems, medical devices, computer architecture and dynamic Nano electromechanical (NEMS) which provides ultra-level of integration, incorporating embedded and IoT devices supporting this technology. Results of analog and digital components showed superiority over other silicon transistor technologies in their ultra-low power consumption and high switching speed.

Metal Organic Frameworks (MOFs) are a class of porous materials that are predominantly obtained as powders and have been investigated as a solid sorbent for gas separation or carbon capture applications from combustion exhaust gases. The manufacturing of products with MOFs to use them for real life applications is still a major problem. The most common productization method used is to form pellets of the powder MOFs. This has a limitation on the product shape which makes it difficult for it to be used in gas separation applications. This study focuses on using additive manufacturing technique to give MOFs a lattice (mesh-like) geometry which is useful for gas separation applications as the mixture of gases would be able to pass through the lattice structure and be separated due to the inherent MOF properties and characteristics. Two MOFs based on magnesium and manganese salts have been studied in this project. An extrudable paste developed using alginate gel as a binder with these MOFs. With alterations in paste formulations and 3D printer parameters, lattice structures were printed using the two MOFs. CO2 and N2 gas uptakes were measured showing that the structure adsorbs CO2 gas to a higher extend which results in the separation of N2 gas in both materials. When compared to their pristine powder form, other properties of the MOFs such as crystallinity, microstructure, reusability and surface area remain to be preserved after being 3D printed in both cases.

Graphene features a unique combination of exceptional properties and has emerged as one of the most promising nanomaterials for a variety of applications. The ability to structurally modify graphene with nanoscale precision enables the properties to be further extended. By introducing nanopores in the graphene lattice, nanoporous graphene can be used in high-performance electronic devices or as selective membranes for efficient molecular filtering. Although methods for deterministic nanopatterning already exists, key for the implementation of nanoporous graphene is the development of a scalable and customisable method of patterning graphene that does not require any lithographic mask that is introducing defects. In this project, a novel approach using a nanoporous mask and a broad beam of 20 keV Ar ions has been investigated. Masks with 60-600 nm circular pores have been fabricated, and by irradiating suspended graphene membranes grown by chemical vapor deposition (CVD) through the mask, nanoporous graphene has been deterministically generated. The masks are fabricated using electron beam lithography, and the pattern is highly customisable regarding pore size, pore distribution and areal coverage. In addition to perforating the graphene, the ion beam is also observed to significantly reduce the level of contamination on the graphene membrane. The proposed mechanism is the combination of electronic  sputtering of surface contaminants and the random diffusion that follows, with a low nuclear sputtering yield and to-site pinning of contaminants. An extension of this study could include a more comprehensive characterization of the nanoporous graphene obtained as well as further studies on the dependency of beam parameters.

Indoor photovoltaics is an emerging technology that could power the Internet of Things (IoT)devices with low energy requirements. The conventional silicon-based photovoltaics is notsuitable for indoor lighting conditions, opening the door for organic photovoltaics (OPV).When fabricating OPV devices, a transparent and conductive electrode is needed. Indium tinoxide is a common transparent for research, but it is expensive and difficult to use in roll-toroll (R2R) production. PEDOT:PSS is a cheap conductive polymer compatible with R2Rprocessing, but its relatively low conductivity limits cell size and geometric fill factor. Addingsilver nanowires to the PEDOT:PSS solution could improve conductivity but raises the risk ofshort-circuiting the devices. In this thesis, organic photovoltaic devices have been fabricatedusing electrodes based on a commercially available solution of PEDOT:PSS dispersed withsilver nanowires to test its viability. Devices utilizing the novel electrode demonstrated aforward current density of 2,905 mA/cm2, dark current density of -1,25E-05 mA/cm2, shortcircuit current density of 0,037 mA/cm2, open-circuit voltage of 0,630 V, and fill factor of76,6%. Performance for devices with the a reference electrode of pure PEDOT:PSS was aforward current density of 0,94 mA/cm2, dark current density of -2,35E-05 mA/cm2, shortcircuit current density of 0,0341 mA/cm2, open-circuit voltage of 0,630 V, and fill factor of76%. However, the resistance in the novel electrode appears to degrade faster than in thereference electrode, even in an inert atmosphere, which motivates further studies ondegradation mode and methods to prevent it.

A key emerging concept within the forensic sciences today areportable measurementdevices, where a much more efficient usage of the resources involved with crime-solving is possible if confirmatory measurements can be realised directly at a crimescene with such devices. Today, the majority of the presently used methods duringcriminal investigation at a crime scene involves measurements of a presumptivenature, which is a vital tool as it enables the screening of samples. In this thesis,the overarching goal is the development of tool kits for the analysis of biosampleson-site at a crime scene. This is mainly investigated through two routes: theusage of Quantum Dots (QDs) as a recognition element in sensory applications andfabrication of a graphene-based device for the detection of illicit drugs.The investigations conducted for the studies presented in this thesis focuses onsensory applications with a forensic detection scheme in mind: study I reveals in-trinsic properties of QDs to better understand sensing mechanisms upon bindinginteractions; study II demonstrates the fabrication of a graphene-based device forthe detection of illicit drugs; study III showcases the functionalised and bioconju-gated of QDs for a specific investigation into a biological process; study IV furtherthe investigation into the possible side-effects of QDs on biological specimens.In study I we numerically and experimentally investigate the intrinsic blinkingcharacteristics of CdSe-CdS/ZnS QDs. This includes a thorough examination of theexperimental parameters of the measurement setup: the bin time and excitationpower. Different mechanisms between the off- and on-state probability distributionsare found, wherein the on-state follows the random telegraph signal theory and theoff-state follows the inverse power law distribution.In study II, the detection of illicit drugs (amphetamine and cocaine) is achievedthrough graphene-based sensors processed to contain metal electrodes with superioradhesion and low contact resistance. The construction of a microfluidic system isfurther realised for a detection of molecules based on non-covalent interactions.With this system, a wavelength-dependent photoactivity for amphetamine and arange of its chemical analogs is demonstrated. A molecule dependent interactionwith the graphene surface is shown of the graphene surface either in the form ofp-doping (cocaine) or n-doping (amphetamine).Study III investigates the endocytic pathway of the vascular cell adhesionmolecule 1 (VCAM1) in Human Umbilical Vein Endothelial Cells (HUVECs) in-iiiivABSTRACTduced by Tumor Necrosis Factorα(TNFα) with the usage of 3-Mercaptopropionicacid coated (3MPA)-QDs and 5-Carboxyfluorescein (5FAM) functionalised and la-belled with VCAM1 binding peptides, respectively. Internalisation of the VCAM1molecules into lysosomes is shown with light microscopy through observations ofdifferent pathways of the 5FAM labelled peptides and functionalised QDs.In study IV we investigate the adverse effects of 3MPA-QDs on the humanairway epithelium by an examination of the calcium response in lung cells upon astimulation with QDs. The cellular response to the deposition of QDs is observedwith light microscopy and electrical measurements as a global increase of Ca2+in the epithelial layers and a transient decrease in the electrical response. Theseobservations imply that the influx of calcium caused by the QD deposition is inducedby mechanical stressIn an additional ongoing study, the age determination of dried blood spotsare investigated with the usage of protein markers commonly found in the blood.Human serum (HS) is spiked with a marker of interest to mimic those of normallevels in adult human males. After which the HS is allowed to undergo an ageingprocess in a 96 well plate and further analysed in terms of the enzymatic activitywith commercially available kits. The preliminary test results show that there is ameasurable change of activity dependenton the utilised marker that may act as abasis for the age determination of dried blod spots / <p>Examinator: Professor Björn Önfelt</p>

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