Continuous scaling of complementary metal oxide semiconductor (CMOS) devices has led to constant increase in device performance. However, as scaling becomes more difficult with every technological node, alternative channel materials that could replace silicon (Si) are being investigated [1]. Germanium (Ge) is an attractive material because of its four times higher hole mobility and twice higher electron mobility compared to silicon [2]. Nevertheless, Ge suffers from surface passivation issues that need further investigation. A modification of oxidation through a barrier layer method proposed by Takagi group[3] has been employed for the fabrication of MOS capacitors. Ozone oxidation has been performed in-situ in atomic layer deposition (ALD) chamber using Al2O3 layer as a barrier. Combinations of barrier thickness and ozone generator power have been investigated together with the influence of the oxidation time. Electrical characterization has revealed that the Ge/oxide interface is improved while employing high ozone generator power oxidation through a thin (~0.47 nm) barrier as well as prolonged oxidation times up to 15 min. Interface state density has been suppressed to lowto mid 1012 cm-2eV-1. / Kontinuerlig skalning av komplementär MOS teknologi (CMOS), har lett till konstant förbättrad prestanda hos integrerade CMOS-kretsar. Fortsatt nerskalning möter dock större hinder för varje teknologinod och forskare undersöker alternativa material till kisel (Si) [1]. Germanium (Ge) är ett attraktivt material eftersom hålmobiliteten är fyra gånger och elektron mobilitet två gånger högre än hos kisel [2]. En utmaning med att bygga CMOOS pp Ge är att det är svårt att passivera Ge. I denna avhandling undersöks en modifikation på metoden att oxidera genom ett barriärlager som föreslagits av gruppen som leds av Takagi [3]. Ozon oxidering har utförts in-situ i en atmoic layer deposition (ALD) kammare där Al2O3 användes som ett barriär lager och MOS kondensatorer har tillverkats och karakteriserats. Kombinationer av barriär tjocklek och ozongeneratoreffekt har undersökts tillsammans med influensen av oxideringstid. Karakterisering av elektriska egenskaper har visat att gränsytan mellan germanium och oxid förbättras då en hög ozongeneratoreffekt används för att oxidera genom en tunn (~0.47 nm) barriär och genom att använda en förlängd oxideringstid upp till 15 min. Defektdensiteten (Dit) vid gränssnittet till Ge sjönk med oxideringstiden och som lägst uppmättes till ~3·1012 cm-2eV-1.

Chemical mechanical polishing (CMP) has emerged as a critical technique for the manufacture of complex integrated circuits to achieve low surface roughness and high degree of planarization. In particular, the continuous progression of the wafer carrier has been driven by the interest of diminishing the waste on a wafer by reducing the edge of exclusion area, and hence, increasing the amount of chips per wafer. In this thesis,a standard wafer carrier and the state of the art Titan™ wafer carrierare compared and evaluated by planarizing a set of blank wafers with a PECVD oxide film on an IPEC 472 CMP tool. The surface roughness was analyzed before and after the planarization step using an atomic force microscope (AFM) and the nonuniformity across the wafer was characterized by ellipsometry. The material removal rate and the reproducibility of the nonuniformity from wafer to wafer was also observed and compared. A second set of experiments with patterned wafers pla-narized with the Titan™ carrier was also performed. The impact of thepattern density in the step height reduction ratio and surface roughness was analyzed with AFM. The results obtained from the blank wafers planarized with the standard wafer carrier showed a nonuniformity average of ± 6.96% with a 3 mm edge of exclusion, a wafer to wafer nonuniformity of ± 4% and a surface roughness of 0.34 nm. However, the Titan™ carrier delivered a nonuniformity average of ± 2.17%, a wafer to wafer nonuniformity of ± 0.3% and a surface roughness of 0.22 nm. The Titan™ carrier outmatched the standard wafer carrier forcing it to shift the edge of exclusion area to 7mm to be able to achieve a nonuniformity of ± 2.90%. The results for the set of patterned wafers showed a step height reduction ratio (SHRR) average of 98.35%. Thesurface roughness for the oxide above the patterned polysilicon structures decreased from 9.46 nm to 0.33nm and the surface roughness on the recessed areas decreased from 3.70nm to 0.7nm.

Density functional theory was employed to investigate the energetics of ABA, ABC, and intermediary stacked phases for both pristine and s-triazine functionalized graphene trilayers. The energy of the ABC-stacked phase relative to the pristine ABA-stacked ground state showed a 94% increase when s-triazine was adsorbed to the graphene surface, confirming previous studies of the ability of s-triazine to facilitate the ABC to ABA phase-transition. This work is outlined in an enclosed publication titled “Trilayer Graphene as a Candidate Material for Phase Change Memory Applications.” Subsequently, low-pressure CVD was used to synthesize single-crystal graphene trilayers of up to 200 µm, the largest reported thus far. The defect density, stacking density, and morphology of the CVD-grown graphene trilayers are evaluated using Raman spectroscopy. The layers are also shown to be directly discernable as-grown on copper substrates using dark-field optical microscopy even without contrast oxidation of the copper film, representing a quick and reliable method for their identification. Slow-etching of the graphene yielded well-aligned, hexagonal domains further indicating the high-quality, single-crystalline of the graphene.

Silicon heterojunction interdigitated back-contact (SHJ-IBC) solar cells have attracted considerable attention because of their potential to achieve very highly efficiency. However, the back contacting scheme leads to additional fabrication complexity mainly resulting from the formation of interdigitated n- (back surface field (BSF)) and p-type (emitter) hydrogenated amorphous silicon (aSi:H) strips. Photolithography is widely used for patterning of the interdigitated strips, but this is a costly and impractical technique for industrial applications. This work focuses on the development of simple BSF/emitter patterning approaches of SHJ-IBC cells to replace photolithography and two methods, selective deposition (SD) and dry etching of a-Si:H, have been evaluated. Selective deposition of materials is a promising approach for electronic device fabrication, which allows materials deposition on pre-defined areas while no deposition occurs on other parts of the device. As a result, costly lithography and etching steps can be avoided. Selective deposition of a-Si:H at low temperature (~200C) using plasma-enhanced chemical vapor deposition (PECVD) technique, is a novel approach for rear side emitter patterning of SHJ-IBC solar cells. The first target of this study was to selectively deposit a-Si:H on crystalline silicon (c-Si) while avoiding deposition on the SiOx mask. The second target was to achieve a sufficient quality a-Si:H/c-Si interface passivation using selectively deposited silicon film. The SD of a-Si:H was realized by short deposition of a-Si:H followed by etching using hydrogen plasma. Hydrogen atoms can selectively eliminate strained bonds in a-Si:H films. Proper hydrogen plasma exposure allows to discriminate between Si-Si bonds on different substrates. As such, substrate-SD of a-Si:H is possible. Repetition of short deposition followed by hydrogen plasma etching leads to net deposition on one substrate, i.e., c-Si, but not on mask layers, i.e., SiOx. Two deposition approaches were used to develop SD. The first approach is "Time-modulated power"; where deposition and etching is controlled by radio frequency power. The second deposition approach is "Time-modulated SiH4", where film deposition and etching is controlled by pulsed SiH4 flow. Spectroscopic Ellipsometry (SE) and Transmission Electron Microscopy (TEM) were utilized to measure selectivity, film thickness, and morphology. Effective carrier lifetime (τeff) was measured to check the c-Si surface passivation quality using Quasi-steady-state photo-conductance (QSSPC) method and Photoluminescence (PL) image. From TEM it was observed that, although selectivity is achieved in this work, crystallization of the deposited Si film on c-Si results in poor passivation quality, which is probably induced by long hydrogen plasma exposure. To reduce the crystallization rate, NF3 plasma treatment was carried out on c-Si surface before SD. The suppression of silicon epitaxial growth was observed. This is due to the transformation of c-Si surface bonding configurations which was confirmed by measurement of Attenuated total reflectance Fourier transform infrared spectroscopy. The QSSPC and PL results indicated improved passivation quality using NF3 plasma treatment before SD. The other part of this study concerned the etching of a-Si:H (n+) layer in i/n+ a-Si:H stack using hydrogen plasma followed by in-situ re-deposition of a-Si:H(p+) layer. With the aid of in-situ deposition, the vacuum break of PECVD, HF dip of c-Si wafer prior to a-Si:H(p+) deposition, wafer rising and drying can be skipped. A sufficient c-Si surface passivation is here required after the etching and re-deposition processes. According to the SE results, a stable and uniform etching of a-Si:H(n+) film with etching rate of 1.4±0.1 nm/min was achieved. An excellent surface passivation quality with τeff of above 8ms was obtained after etching of a-Si:H(n+) and re-deposition of a-Si:H(p+) layer. A thicker a-Si:H(i) layer was proven to be beneficial to prevent passivation degradation during hydrogen plasma etching. The preliminary results suggest that this is a promising method to replace currently used etching methods that remove the whole a-Si:H(i/n+) stack, significantly simplifying rear side patterning steps for SHJ -IBC solar cell devices.

The design of pathogen biosensors may soon incorporate beads having a nanoscale diameter, thus making the drag force on a nanoscale sphere an important engineering problem. Flows at this small of a scale begin to appear "grainy" and may not always behave as a continuous fluid. Molecular dynamics provides an approach to determine drag forces in those nanoscale flows which cannot be described with continuum (Navier-Stokes) theory. This thesis uses a molecular dynamics approach to find the drag forces acting on a sphere and a wall under several different conditions. The results are compared with approximations from a Navier-Stokes treatment and found to be within an order of magnitude despite the uncertainties involved in both the atomic interactions of the molecular dynamics simulation and the appropriate boundary conditions in the Navier-Stokes solution. / Master of Science

Silicon-based nanostructures are essential building blocks for nanoelectronic devices and nano-electromechanical systems (NEMS). As the silicon device size continues to scale down, the surface to volume ratio becomes larger, rendering the properties of surfaces and interfaces more important for improving the properties of the nano-devices and systems. One of those properties is the friction, which is important in controlling the functionality and reliability of the nano-device and systems. The goal of this dissertation is to investigate the deformation and friction behaviors of single crystalline silicon nanolines (SiNLs) using nanoindentation techniques. Following an introduction and a summary of the theoretical background of contact friction in Chapters 1 and 2, the results of this thesis are presented in three chapters. In Chapter 3, the fabrication of the silicon nanolines is described. The fabrication method yielded high-quality single-crystals with line width ranging from 30nm to 90nm and height to width aspect ratio ranging from 10 to 25. These SiNL structures have properties and dimensions well suited for the study of the mechanical and friction behaviors at the nanoscale. In Chapter 4, we describe the study of the mechanical properties of SiNLs using the nanoindentation method. The loading-displacement curves show that the critical load to induce the buckling of the SiNLs can be correlated to the contact friction and geometry of SiNLs. A map was built as a guideline to describe the selection of buckling modes. The map was divided into three regions where different regions correlate to different buckling modes including Mode I, Mode II and slidingbending of SiNLs. In Chapter 5, we describe the study of the contact friction of the SiNL structures. The friction coefficient at the contact was extracted from the loaddisplacement curves. Subsequently, the frictional shear stress was evaluated. In addition, the effect of the interface between the indenter and SiNLs was investigated using SiNLs with surfaces coated by a thin silicon dioxide or chromium film. The material of the interface was found to influence significantly the contact friction and its behavior. Cyclic loading-unloading experiments showed the friction coefficient dramatically changed after only a few loading cycles, indicating the contact history is important in controlling the friction behaviors of SiNLs at nanoscales. This thesis is concluded with a summary of the results and proposed future studies. / text

ANGLICKÝ ABSTRAKT This master's thesis analyses European legal framework on handling chemical substances. Primary focus of this thesis is on the Regulation (EC) No 1907/2006 of the European Parliament and of the Council concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals, establishing a European Chemicals Agency. A part of the thesis is dedicated to comparing analyses between American and Europeans legal framework and part is also dedicated to an attempt of monetary cost-benefits evaluation of this regulation. The thesis covers also the nanoparticles regulation and Regulation (EC) No 1272/2008 on classification, labelling and packaging of substances and mixtures. Powered by TCPDF (www.tcpdf.org)

A variety of open and closed multi-layered nanoparticle structures have been considered analytically and numerically for their use as scatterers and radiators. These include metamaterial-inspired structures based on dielectrics and metals excited by either plane waves or electric Hertzian dipoles at optical frequencies. Both passive and active (gain impregnated dielectric) materials have been considered. Enhanced and mitigated scattering and radiating effects have been modeled. Nano-antenna and nano-amplifier configurations for optical applications have been emphasized. A review of these modeling efforts will be presented.

Atualmente, nanopartículas (NPs) são utilizadas em todos os ramos da tecnologia. Suas promissoras aplicações envolvem entre outros, o campo dos sensores e transdutores, mídia de gravação magnética, carreadores magnéticos de drogas medicinais. Com o objetivo de produzir NPs pelo método físico, um gerador de nanopartículas foi adaptado usando um dos canhões do sistema de magnetron sputtering, baseando-se no método de agregação gasosa. Com o gerador somos capazes de produzir NPs de diversos materiais e codepositá-las em matrizes dielétricas ou metálicas. Neste trabalho apresentamos o desenvolvimento da metodologia para a produção de nanopartículas de materiais magnéticos duros, usando alvos de SmCo5, Sm2Co17, Nd2Fe17B, FePt e CoPt. Investigamos a influência dos parâmetros de deposição (pressão, fluxo de gás e potência de sputtering), tipo de substrato e a existência de buffer e/ou codeposição, na obtenção das propriedades estruturais e magnéticas desejadas para esses materiais. As NPs produzidas são analisadas magneticamente pelo VSM e SQUID, sua morfologia e tamanho por TEM e SEM, a sua estequiometria pelo RBS, e a sua estrutura cristalina por XRD, a fim de obter nano-ímãs de alta anisotropia magnética. Da caracterização morfológica, através de microscopia eletrônica, encontramos para as NPs produzidas e estudadas diâmetros entre 5 e 17 nm. Através de análises de RBS obtemos para composição das NPs que as mesmas possuem estequiometria diferente dos alvos usados. Estudos estruturais e magnéticos mostram que para Sm-Co, Fe-Pt e Co-Pt é possível obter NPs cristalinas e com coercividade da ordem de 1 kOe. / In the recent years, nanoparticles (NPs) are being in all fields of technology. Their promising applications involve among others, the field of sensors and transducers, magnetic recording media, magnetic carriers of medicinal drugs. Aiming to produce NPs by physical method, a generator of nanoparticles was adapted using a system of guns \"magnetron sputtering\", based on the aggregation gas method. With the generator we are able to produce NPs with different types of material. In this work, we present the development of the methodology for the production of nanoparticles of hard magnetic materials, using targets of SmCo5, Sm2Co17, Nd2Fe17B, FePt and CoPt. We investigated the influence of the deposition parameters (pressure, gas flux and sputtering power), substrate type and the existence of the buffer and/or codeposition layers, to obtain the desired structural and magnetic properties for the nanoparticles. The produced NPs were magnetically analyzed by VSM and SQUID, the morphology and size by TEM and SEM, the stoichiometry by RBS and the crystal structure by XRD. The main objective of this work is to obtain nano-magnet with high magnetic anisotropy. Through the morphological characterization by electron microscopy, we found for NPs produced and studied have diameters between 5 and 17 nm. Through RBS analysis we have obtained the composition of the NPs, and also that they have different stoichiometry in relation to the used targets. Structural and magnetic studies have show that for Sm-Co, Fe-Pt and Co-Pt it is possible to obtain crystalline NPs with coercive field around 1 kOe.

The effect of nano-structured surfaces on pool boiling heat transfer is explored in this study. Experiments are conducted in a cubical test chamber containing fluoroinert coolant (PF5060, Manufacturer: 3M Co.) as the working fluid. Pool boiling experiments are conducted for saturation and subcooled conditions. Three different types of ordered nano-structured surfaces are fabricated using Step and flash imprint lithography on silicon substrates followed by Reactive Ion Etching (RIE) or Deep Reactive Ion Etching (DRIE). These nano-structures consist of a square array of cylindrical nanofins with a longitudinal pitch of 1 mm, transverse pitch of 0.9 mm and fixed (uniform) heights ranging from 15 nm – 650 nm for each substrate. The contact angle of de-ionized water on the substrates is measured before and after the boiling experiments. The contact-angle is observed to increase with the height of the nano-fins. Contact angle variation is also observed before and after the pool boiling experiments. The pool boiling curves for the nano-structured silicon surfaces are compared with that of atomically smooth single-crystal silicon (bare) surfaces. Data processing is performed to estimate the heat flux through the projected area (plan area) for the nano-patterned zone as well as the heat flux through the total nano-patterned area, which includes the surface area of the fins. Maximum heat flux (MHF) is enhanced by ~120 % for the nanofin surfaces compared to bare (smooth) surfaces, under saturation condition. The pool boiling heat flux data for the three nano-structured surfaces progressively overlap with each other in the vicinity of the MHF condition. Based on the experimental data several micro/nano-scale transport mechanisms responsible for heat flux enhancements are identified, which include: “microlayer” disruption or enhancement, enhancement of active nucleation site density, enlargement of cold spots and enhancement of contact angle which affects the vapor bubble departure frequency.