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Single walled carbon nanotubes (SWCNTs) are carbon based nanostructures with extraordinary electronical and mechanical properties. They are used in a wide range of applications, usually embedded in polymer as fillers to form polymer based nanocomposites, in order to affect the electronic behavior of the polymer matrix. However, as the nanotubes properties are directly dependent on their intrinsic structure, it is necessary to select specific nanotubes depending on the application. In addition, as randomly oriented CNTs (as Filler) embedded in the polymer matrix show lower electrical conductivity than expected, alignment of CNTs in the polymer matrix can help to improve the nanocomposite electrical conductivity. In this thesis, focus is placed on the electrical properties of the produced SWCNTs/Polymer nanocomposites. A simple patterning method called nanoimprint lithography is presented which allows the use of extremely low amounts of nanotubes in order to increase the electrical conductivity of isolated polymers such as polystyrene (PS). In addition, a flexible mold to pattern nanocomposite films, leading to the creation of conducting nanotube networks, resulting in Alignment of SWCNTs (from the bottom of the film to the top of the imprinted patterns) inside the polymer matrix. The project further investigated the effect of different imprint temperatures and pressures on the electrical conductivity of produced nanocomposite and a trend is found due to the variation of parameters. Finally an optimum imprint condition based on maximum achieved conductivity is suggested. During different steps of sample preparations, the samples were characterized by different microscopic and spectroscopic techniques such as Atomic Force Microscopy (AFM), optical microscopy, Spectroscopic Ellipsometer, electrical measurements and Raman spectroscopy.

In this master thesis the effects of the process parameters of pp-HMDSO were studied in the application of corrosion protection of an Al surface. The method for polymerising the HMDSO vapour was RF-PECVD. The following process parameters were studied: RF-power, flow of HMDSO, Oxygen as reactive gas, Ar as inert gas, the effect of applied bias voltage, as well as Ar etch as pre-treatment and subjecting the film to a pure O2 plasma as post-treatment. The results were a prolonging of the total decay time of the Al film when subjected to a 1M NaOH solution. The decay time increased from 5-20s for an unprotected Al film to 140min for the best pp-HMDSO coating. SEM/EDX, XRR, L*a*b* were used when analysing the pp-HMDSO films. The best performing coatings were tested on reflectors and passed the industry standard test of being subjected to a 0.1M NaOH for 5min without visible corrosion or decay.

In line with The Paris Agreement, the world is now changing towards more sustainable options for all sorts of energy development. The solar energy sector is growing rapidly as a result of this. One area that holds great potential in changing many of the worlds heating processes, is concentrating solar power (CSP). The basic principle of CSP is to reflect incoming sunlight and concen- trate it to heat a fluid. To do so, it is crucial to find a reflector material that shows both good optical performance initially as well as over time to produce heat in the most efficient way possible and compete with the fossil fueled options. In this investigation, four different, commercially available reflecting materi- als, for concentrating solar power, have been tested under accelerated aging conditions to simulate the wear of outside conditions for many years. Impacts from humidity, temperature fluctuations, UV radiation and acid rain have been included in the study. From the results, it will be argued that a silver based polymer film is the best option, out of the four tested, in terms of the combination of durability and high reflectance properties. However, conclusions about how to properly mea- sure the reflectance of a solar reflector is also presented and advices on how to get reliable results in a similar investigation in the future is presented.

The recent development of photonics and applications puts new challenges for systems using emission, transmission and modulation of light. For these reasons, novel optical materials attract a special interest for their enabling properties for novel technologies. In this work, we performed the research on fundamental properties and the possibility of implementation of electro-optical response of Poly-3-hexylthiophene-2,5-diyl (P3HT) nanofibers, which belong to the class of organic semiconductor crystalline materials. Our research demonstrated that an external electric field allows controlling the orientation of nanofibers dispersed in a solution by changing the electrical properties of P3HT crystals. This method was used to introduce a collective alignment of P3HT nanofibers and to impact the optical properties of the colloid. The spectroscopic and polarization measurements show that P3HT nanofibers possess optical anisotropy in a wide range of visible spectrum. This property combined with the ability to manipulate the orientation of nanofibers dynamically, was used for direct phase and intensity modulation of transmitted light. Along with these investigations, several engineering and technology tasks were solved. We have designed the transverse electro-optical cell using all-optical-fiber approach, as well as the longitudinal electro-optical cell was fabricated using a novel polymer molding technique. The obtained research results demonstrate the potential of P3HT crystalline nanofibers as a material class of large niche of applications, not only limited to photovoltaics but also being implemented in electro-optical systems to control light polarization and propagation. / <p>QC 20171229</p>

Thermoelectric materials are important in today’s society with a variety of applications. The material properties that determinate the efficiency of a thermoelectric device are mostly constants. In order to develop more efficient thermoelectric devices new materials and solutions need to be made. Minimizing the thermal conductivity in thermoelectric materials is of great interest to make them more effective.   One effective way of lowering the thermal conductivity is to introduce holes in the lattice and create a phononic crystal. The main focus of this master thesis has been on how to place these holes and to optimize the geometry to minimize thermal conductivity. The method used in this report is based solely on simulations, which were done using Comsol Multiphysics 5.2a. The results are compared to already published results. Different geometries are tested to see how it affects the thermal conductivity and to optimize the phononic crystal. The Maxwell-Eucken model is also used to see how porosity affects the thermal conductivity and to analyze what the lowering in thermal conductivity depends on.   The result showed a substantial reduction in thermal conductivity when creating a phononic crystal compared to bulk silicon. The simulated reduction compared to bulk silicon is up to 98.5% when introducing holes in the lattice, while Maxwell-Eucken only predicted a 74% reduction due to porosity.   The conclusion is that by creating holes in a periodical pattern, phonon dispersion will occur, which lower the thermal conduction significantly.

No description available.

The atom probe is an analysis technique based on the emission of ionized species from a needle-shaped sample (apex radius &lt; 100 nm) under the influence of a very strong electric field ( 10-50 V/nm). A DC-voltage is applied on the sample in order to generate a field slightly below the one necessary to remove atoms (in the form of ions) from its surface. An ultrashort (femtosecond) laser pulse is used to trigger the emission. The evaporated ions are accelerated in the electric field and projected onto a position sensitive detector where a magnified image of the surface is formed (magnication from 10^6 to 10^7). Time of flight mass spectrometry is used to chemically identify the evaporated atoms. The technique thus allows to analyze the composition of a 3D volume with sub-nanometer resolution. Imec conducts research in order to introduce the 3D characterization with quasi-atomic resolution capabilities of the technique to the semiconductor industry. It became quickly apparent that a detailed understanding of the laser interaction with the nanoscale samples is crucial in order to interpret the analysis results. In this work, we briefly introduce the principles of the technique and review some of its applications. We then summarize some of the currently unexplained experimental observations, taken from the literature or from experiments conducted at Imec. Based on those observations, we introduce a thermally assisted model of field evaporation that includes the electromagnetic nature of light and the semiconducting character of silicon. The optical absorption of the nanoscale sample is computed by numerical simulations using the FDTD algorithm. The temperature evolution at the tip apex is obtained by solving a coupled thermal conduction-carrier recombinations problem and the shape of the mass spectrum is deduced. We discuss the model and confront its results to experimental data. We show that the model qualitatively explains many experimental aspects of the characterization of silicon by means of an atom probe analysis. Nevertheless, we show that at this stage the model lacks quantitative accuracy and we suggest several ways to improve it. / atom probe, LA-WATAP, field evaporation, femtosecond laser pulse interaction with nanoscale silicon objects, Sommerfeld's half plane problem, FDTD - Yee's scheme.

In this project, nanopore arrays have been fabricated on bulk silicon and on silicon membranes by electrochemical etching. First, the surface of bulk silicon and silicon membranes have been patterned by photolithography and then invert pyramidal pit arrays have been formed by KOH etching. To fabricate nanopore arrays, bulk silicon and silicon membranes with the inverted pyramidal structure were electrochemically etched with backside illumination and by breakdown methods, respectively. Pore morphology was then characterized by scanning electron microscopy (SEM). On bulk silicon, etching by backside illumination did not form promising nanopore arrays; while arrays of nanopores with ~8 nm in diameter have been fabricated to a depth of 18 μm by tuning the applied breakdown bias. On silicon membranes, arrays of nanopores with 18±4 nm diameter have been etched through the membranes with the buried oxide remaining on the backside using the breakdown method.

Intermodulated force microscope (ImAFM) is a type of dynamic AFM. ImAFM opens up possibilities for mapping the topography and making quantitative determinations of material parameters at the same time. With increased information the need to generate more informative images of the sample emerges. In this Bachelor's degree project I have created tools for rendering images of a sample. The topography is plotted as the height and a material parameter is color coded on topography. Shadows and reflections are important for the eye's interpretation of height differences in a image so the tools created in this project will meet this need. / Intermodulerat Atomkraftmikroskop (ImAFM) är en typ av dynamisk AFM. Med ImAFM finns möjlighet för kartläggning av topografin och kvantitativa bestämningar utav fleramaterial parametrar för provet. Med ökad information kommer behovet om att bygga upp mer informativa bilder utav det scannade provet. I detta kandidatexamensarbete skapas verktyg för att rendera bilder utav provet. Topografin plottas som höjden och materialparametern färgkodas och läggs ovan på topografin. För att få förståelse för höjdskillnader i en bild är skuggor och reflektioner viktiga för ögat. Verktygen som skapas inriktas på att tillgodose detta behov.