No description available.

No description available.

The work carried out for this thesis focussed on four main areas: (i) the examination and optimisation of the conditions for carbon nanofibre (CNF) growth, both unsupported and as films on substrates; (ii) the electrochemical characterisation of the CNF material before (as-grown) and after solubilisation (oxidation); (iii) the formation and investigation of CNF thin film electrodes; and (iv) the (co-)deposition of the CNFs with metals from aqueous plating solutions. CNFs are grown at an iron nanoparticle catalyst produced from an iron oxide precursor. After exploratory work with different types of iron oxide precursors, a suitable and universally applicable catalyst is identified. CNFs are characterised by electron microscopy, spectroscopy, and electrochemistry. When grown onto a ceramic substrate, the 'as-grown' CNF material is shown to act as a porous, high surface area electrode with the ability to strongly adsorb aromatic molecules, such as hydroquinone, benzoquinone, and phenol.

This thesis is dedicated to the production and analysis of thin hydrogenated amorphous carbon films. A cascaded arc plasma source was used to produce a high density plasma of hydrocarbon radicals that deposited on a substrate at ultra low energies. The work was intended to create a better understanding of the mechanisms responsible for the film formation, by an extensive analysis on the properties of the films in correlation with the conditions used in the plasma cell. Two different precursors were used: methane and acetylene. They revealed a very different picture for the mechanism of film formation and properties. Methane was less successful, and the films formed were soft, with poor adhesion to the substrate and decomposing with time. Acetylene was the better option, and the films formed in this case were harder, with better adhesion to the substrate and stable over time. The plasma parameters could be varied to change the character of films, from polymer-like to diamond-like carbon.

The growth of graphene on Ni thin films using several different methods is discussed. These methods include no intentional introduction of carbon, immersion in an organic solvent, exposure to carbon-containing gas and a solid state approach by decomposition of molecules. All the methods have produced single layer graphene over a large area. We suggest that the graphene formation without intentional introduction of carbon involves conversion of carbon-containing adsorbates on Si02. This process has been verified by our experiment of graphene growth by decomposition of C6O, in which C60 is deposited on top of Si02 and buried under Ni thin film. Single layer graphene has successfully formed which suggests that the carbon from C60 has diffused and segregated to the top of the Ni surface. So we investigate the effect of outgassing aimed to eliminate adsorbates on Si02. Graphene growth by immersion in an organic solvent was initially performed to investigate the effect of outgassing process, and single layer graphene is formed but is highly defective, as determined by the intensity of the Raman D band. We found that outgassing the Si02 is important to produce single layer graphene, but the defects in graphene are not significantly reduced. Graphene growth method using propylene is carried out to identify the factors that influence the amount of defects and to reduce through optimization of growth parameters. The graphene defects are reduced significantly by varying the annealing temperature and exposure time to propylene. We found that different Ni thickness do not affect the defect formation in graphene but do improve the Ni surface morphology. Graphene growth by decomposition of C60 on Ni thin film produced graphene layers with controlled thickness. This molecular carbon source provides a method of controlling the total dosage of carbon introduced into the film with a high degree of precision. We found that the C60 coverage, annealing temperature, and deposition sequence influence the properties of graphene layers. We also presented preliminary results of graphene enhanced Raman scattering (GERS) of adsorbed PTCDI. We demonstrate that single layer graphene is a very good substrate for Raman enhancement in which the adsorbed molecules can be detected at a small fraction of monolayer coverage. Using the same transfer method typically used for graphene, we managed to transfer PTCDI on graphene from Ni film to Si02. Here we demonstrate the effect of a substrate for graphene which can give rise to the enhancement of a Raman signal of adsorbed molecules.

This work describes the investigation of self-assembled monolayers (SAMs) with scanning tunnelling microscopy/spectroscopy (STM/S) and infrared laser-driven STM (LDSTM). As a tool STM is uniquely able to resolve atoms on a surface. Illuminating an STM with infrared radiation tuned to match modes in the SAM used as the sample provides a unique opportunity to investigate the combination of the well understood character of organic molecules with the atomic scale resolution of an STM. SAMs were prepared with octanethiol and dimethyl disulphide on Au(111) substrates. STM images and STS spectra of these samples recorded at 78K are presented. Typical surface features are observed in the octanethiolate monolayers. The results of STS experiments with an octanethiolate monolayer reveal correlations between surface features and conductivity at -1.0V. The differences between these STS data and equivalents from uncoated samples reveal the effect of the molecules upon the! elect ronic surface states of the samples. Images of samples prepared with dimethyl disulphide show previously unseen low density structures and individual molecules scattered across the surface. Correlations are made between these low density structures and the reconstruction of the underlying gold surface. Comparisons with previously calculated models are used to identify these isolated molecules. STS data collected across a section of sample show how topography data can be used to categorise STS data. The response of the laser-STM interaction to the laser modulation is presented and compared with that of the STM alone. The modulation of the tunnelling current is found to be proportional to the equilibrium tunnelling current which is consistent with theoretical models. This response of the laser-STM interaction to the laser modulation frequency was found to differ between Au(111) substrates uncoated and coated with a methylthiolate SAM. Correlations were observed between! the f requency response of the laser-STM interaction and the STS data.

Orientador: Vladimir Prokofievich Poliakov / Co-orientador: Carlos José de Mesquita Siqueira / Dissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduaçao em Engenharia Mecânica. Defesa: Curitiba, 2005 / Inclui bibliografia e anexos / Resumo: Pesquisas em aplicações de materiais avançados em próteses artificiais que apontam em minimizar as complicações biomecânicas de materiais implantados é atualmente de grande interesse. O desgaste provocado por pequenas partículas geradas do polietileno do peso molecular ultra alto (UHMWPE), usado geralmente no material de implante da taça acetabular da articulação coxo-femural foi reduzido ultimamente por um fator 30-600, revestindo as partes metálicas com um filme duro de DLC. A presença das partículas do polietileno são consideradas o principal fator que induz à osteólise. As tentativas precedentes em se revestir o UHMWPE com filmes finos duros resistentes ao desgaste pelo método CVD (Deposição Química de Vapor) e em combinação com métodos diferentes por PVD (Deposição Física de Vapor) não obtiveram sucesso. O trabalho atual inclui resultados de caracterização físico-química, de propriedades mecânicas (nanodureza, módulo elástico) e de testes tribológicos de filmes duros DLC depositados no UHMWPE. A caracterização físico-química dos filmes DLC foram realizadas por Espectroscopia Raman (RS), Análise de Reação Nuclear (NRA) e Microscopia Eletrônica de Varredura (MEV). Os resultados da análise de Espectroscopia Raman dos filmes DLC PVD e DLC CVD depositados em UHMWPE são diferentes daqueles para os filmes DLC PVD sem hidrogênio e assemelham-se aos resultados dos filmes DLC CVD com hidrogênio. Todo filme depositado por PVD e CVD em polietileno contêm hidrogênio. O teor de hidrogênio dos filmes DLC PVD são menores (6.0 %) do que os depositados por CVD (23 - 25%) analisados por NRA. A nanodureza e o módulo elástico dos filmes DLC PVD com espessuras de 0,25 ?m e 1?m sobre UHMWPE apresentaram valores da ordem de 10 GPa e 50-100 GPa respectivamente. A nanodureza é sensivelmente maior do que para os filmes de DLC CVD (0,6 GPa). O comportamento tribológico foi estudado por deslizamento recíproco através de um tribômetro linear. Verificou-se que o coeficiente de atrito variou de 0,12 para o UHMWPE não revestido a 0,18 para o DLC PVD e DLC CVD após quarenta mil ciclos. Para ensaios mais longos, há uma tendência de redução o coeficiente de atrito para o DLC PVD, mostrando maior poder de lubrificação. Quanto ao desgaste, mostrou-se que as taxas apresentadas pelo UHMWPE revestido por DLC PVD é equivalente ao do material não revestido, para ensaios até duzentos mil ciclos. Os resultados encontrados até o momento, para as condições de deposição dos filmes utilizados neste trabalho não sugerem que o revestimento do UHMWPE seja uma alternativa promissora para minimizar as complicações biomecânicas associadas à articulação do implante. / Abstract: Research in advanced materials aplications in artificial prosthetics aiming to minimize the biomechanical complications of the implanted materials is presently of great interest .The wear of Ultra High Molecular Weight Polyethylene (UHMWPE) particulate commonly used in hip joints as material for acetabular cup was lately decreased by a factor 30-600 by coating metallic substrates with a hard DLC film. The wear generated by particulates of polyethylene are considered to be the main origin inducing osteolysis. Previous attempts to cover UHMWPE with hard wear resistant thin films by CVD (Chemical Vapour Deposition) method and also in combination with different PVD (Physical Vapour Deposition) methods had not been succeeded . The present work includes the results of the physical chemical characterization, mechanical properties (nanohardness , elastic modulus ) and tribological tests of hard DLC films deposited on UHMWPE . Physical chemical characterization of DLC films they had been carried through Raman Spectroscopy (RS) , Nuclear Reaction Analysis (NRA) and Scanning Electron Microscopy (SEM) The results of Raman Spectroscopy analysis of DLC PVD and DLC CVD films deposited on UHMWPE are different from those for hydrogen free DLC PVD films without hydrogen and resemble it the results of films DLC CVD with hydrogen. All of that films PVD and CVD deposited on polyethylene substrates contain hydrogen . Content of hydrogen in carbon films DLC PVD are smaller (6,0 %) than that in CVD (23 - 25%) analyzed by NRA . The nanohardness and elastic modulus of DLC PVD with thickness from 0,25 ?m - 1,0?m deposited on UHMWPE obtained values in the order of 10 GPa and 50-100 GPa respectively. The nanohardness is noticeably larger than those for DLC CVD films (0,6 GPa). The tribological behavior was studied by reciprocating sliding through linear tribometer.It was verified that the friction coefficient varied of the 0,12 for the UHMWPE not coated to 0,18 for DLC PVD and DLC CVD after forty thousand cycles. For longer tests, it has a reduction trend of the friction coefficient for DLC PVD, showing greater to be able of lubrication. About the wear, revealed that the rates presented for the UHMWPE coated for DLC PVD are equivalent to the material not coated, for tests up to two hundred thousand cycles. The results found until the moment, for the conditions from deposition of the films used in this work do not suggest that covering of UHMWPE is a promising alternative to minimize the biomechanics complications associates to the joint of the implantation.

Ein grundlegender Trend der modernen Mikro- und Optoelektronik ist die sinkende Größe der aktiven Elemente der Bauteile. Mit typischen Dimensionen im Bereich 1-10 nm werden Effekte des sogenannten quantenmechanischen Confinements bemerkbar, die die elektronischen und phononischen Eigenschaften der Materialien stark beeinflussen. Der aktuelle Entwicklungsstand von Nanotechnologie macht es möglich, Halbleiternanokristalle mit verschiedenen Strukturparametern wie Größe, Form und chemischer Zusammensetzung herzustellen, welche neue fundamentaleтhysikalische Eigenschaften zeigen. Gleichzeitig ist die Herausforderung, die Zusammenhänge von Struktur der Nanokristalle mit deren optischen, elektronischen und phononischen Eigenschaften zu erkunden, weiterhin relevant. Der Grund dafür besteht darin, dass klassische optische Methoden zur Untersuchung von makroskopischen Materialien und dünnen Schichten – Raman-, Infrarot- und Photolumineszenz-Spektroskopie, bei Anwendung auf Nanostrukturen nicht einzelne, sondern gleich eine Vielzahl von Nanoobjekten mit unterschiedlichen Größen, Formen, Zusammensetzungen etc. messen. Als Resultat davon sind die gemessenen Werte nicht sehr aussagekräftig, da effektiv über eine große Anzahl von Nanokristallen gemittelt wird, während der Beitrag von einzelnen Nanokristallen unter dem Detektionslimit liegen. Aus diesem Grund wurden die Methoden der plasmonverstärkten optischen Spektroskopie, inklusive oberflächenverstärkter Ramanstreuung (SERS, Surface Enhanced Raman Spectroscopy), Photolumineszenz (SEPL, Surface Enhanced Photoluminescence) und Infrarotabsorption (SEIRA, Surface Enhanced IR Absorption) in den letzten Jahren mit dem Ziel, das erreichbare Signal einzelner Halbleiternanostrukturen zu verbessern, stark vorangetrieben. Diese Methoden basieren auf der lokalen Verstärkung des elektromagnetischen Feldes nahe metallischer Nanostrukturen durch das Anregen lokalisierter Oberflächenplasmonenresonanz (LSPR, Localized Surface Plasmon Resonance) mittels Licht im sichtbaren oder infraroten Spektralbereich. Diese oberflächenverstärkten Methoden erlauben das Untersuchen des Phononenspektrum aus SERS-, SEPL- und SEIRA-Daten mit einer Sensitivität weit über der von konventionellen Methoden. Daher wurden in dieser Arbeit SERS- und SEPL-Experimente an CdSe/CdS Nanoplättchen, die auf Gold Nanoscheiben abgeschieden wurden, durchgeführt. Resonantes und nichtresonantes SERS sowie der Einfluss von Energietransfer und Purcell-Effekt in SEPL-Experimenten werden hier gezeigt. Mittels numerischer Simulation wurde die Struktur der Mikro- und Nanoantennen optimiert, um die Übereinstimmung ihrer LSPR- und der Phononenenergien der Halbleiternanokristall-Monolagen in SEIRA-Experimenten zu erreichen. Damit wurden die phononischen Eigenschaften dieser Halbleiternanokristall-Monolagen untersucht, was vorher mit konventioneller IR-Spektroskopie nicht möglich war. Ebenso wurde gezeigt, dass die Plasmonen der Nanoantennen effektiv mit darunterliegenden Materialien, z.B. SiO2, gekoppelt werden können. Die Eindringtiefe dieser Kopplung wurde durch Messung an Nanoantennen auf verschieden dicken SiO2-Lagen bestimmt und die Plasmon-Phonon-Wechselwirkung, die zur Renormalisierung von Phononen- und Plasmonenspektren führt, gefunden. Teile der Arbeit sind in J. Chem. Phys., 153, 16, 2020, Beilstein J. Nanotechnol., 9, 2646–2656, 2018, J. Phys. Chem. C, 121, 10, 5779–5786, 2017, und Beilstein J. Nanotechnol. 7, 1519–1526, 2016 veröffentlicht. Es ist zu beachten, dass die Grenze des Auflösungsvermögens für Optik auch für die oberflächenverstärkte Spektroskopie gilt. Um diese Grenze zu umgehen wurde spitzenverstärkte Ramanspektroskopie (TERS, Tip Enhanced Raman Spectroscopy) verwendet. TERS kombiniert die hohe räumliche Auflösung von AFM (Rasterkraftmikroskopie, Atomic Force Microscopy) mit den analytischen Fähigkeiten der Ramanspektroskopie. Eine Möglichkeit, das lokale elektromagnetische Feld und damit auch das gemessene TERS-Signal zu verstärken, besteht darin, plasmonische Substrate zu verwenden, wobei das zu untersuchende Objekt zwischen diesem Substrat und der Spitze des TERS-Spektrometers platziert wird, da dort die Verstärkung des elektromagnetischen Feldes am größten ist (sogenanntes gap-mode TERS). Daher haben wir in dieser Arbeit den Einfluss eines solchen plasmonischen Substrates auf die TERS-Messungen von phononischen Eigenschaften extrem dünner Lagen (Submonolage) von Nanokristallen untersucht. Vorteile verschiedener TERS-Methoden werden demonstriert: konventionelles TERS, gap-mode TERS und resonantes gap-mode TERS. TERS-Mapping wurde auf den gleichen Nanoscheiben mit CdSe-Nanokristallen durchgeführt und der Unterschied dieser Mappings für zwei verschiedene, für die Ramanspektroskopie genutzte Wellenlängen mit elektrodynamischer Modellierung erklärt. Mit gap-mode TERS war es möglich, einzelne CdSe/CdS Nanoplättchen sichtbar zu machen und ihre Phononenmoden zu erforschen. Teile dieser Arbeit sind in Nanoscale Adv., 2, 11, 5441–5449, 2020 veröffentlicht. Eine weitere neue und intensiv vorangetriebene Methode zur Nanoanalyse ist die nano-FTIR (Fourier Transformed Infrared Spectroscopy, Fouriertransformierte Infrarotspektroskopie) genannte Kombination von IR-Spektroskopie mit Rasterkraftmikrokopie. Im Gegensatz zu TERS, bei dem Licht von einer einzelnen, schmalen Laserlinie inelastisch gestreut wird, verwendet nano-FTIR eine breitbandige Infrarotquelle. Daher wird in nano-FTIR das gesuchte Nahfeld-Signal durch Demodulation des Detektorsignals extrahiert. Durch nano-FTIR-Spektroskopie wurde in dieser Arbeit der Oxidgehalt x in SiOx-Nanodrähten auf der Nanometerskala bestimmt. Weiterhin wurden Plasmon-Phonon-Wechselwirkungen einer einzelnen Nanoantenne auf Si/SiO2 Substrat ebenfalls auf der Nanometerskala untersucht. Teile dieser Arbeit sind in Appl. Surf. Sci., 152583, 2022 veröffentlicht. Zuletzt demonstriert diese Arbeit auch die Kombination von polarisiertem TERS und nano-FTIR für die Untersuchung von hexagonalen AlN-Nanoclustern. Es wird gezeigt, dass die polarisierten TERS-Experimente sensitiv sind für Oberflächenplasmonenmoden mit unterschiedlichen Symmetrien, wie sie charakteristisch für AlN-Nanocluster sind. Der Einfluss der Polarisierung auf die TERS-Mappings eines einzelnen AlN-Clusters und Nanodrahts wird experimentell gezeigt und erklärt. Weiterhin konnte festgestellt werden, dass die nano-FTIR-Spektren, ähnlich den TERS-Daten, eine Sensitivität für Oberflächenmoden zeigen und neue Informationen über die Winkelverteilung dieser AlN-Oberflächenphononen im Nanokristall auf der Nanometerskala liefern.:Table of Contents 1. Elementary excitations in hybrid semiconductor/metal nanostructures 10 1.1. Phonons and excitons in semiconductor nanocrystals: Raman, IR and PL spectroscopies 11 1.2. Raman scattering 15 1.3. Plasmons in metal nanoclusters 17 1.4. Photoluminescence 20 1.5. Surface-enhanced Raman spectroscopy (SERS), IR absorption (SEIRA), and Photoluminescence (SEPL) in hybrid semiconductor/metal nanostructures: Principles and enhancement mechanisms 22 1.6. Tip-enhanced Raman spectroscopy (TERS) and Photoluminescence (TEPL) of semiconductor nanostructures 24 1.7. From conventional Fourier transform infrared (FTIR) to nano-FTIR spectroscopy 26 1.8. Summary 27 2. Experimental Methods 28 2.1. Fabrication of metal nanostructures 28 2.1.1. Metal evaporation 28 2.1.2. Fabrication of TERS cantilevers 28 2.1.3. Photo- and Nanolithography of metal micro-and nanostructures 28 2.2. Fabrication of semiconductor nanocrystals by Langmuir-Blodgett technology and their TEM characterization 32 2.3. Fabrication and TEM characterization of CdSe/CdS nanoplatelets 35 2.4. Fabrication of SiOx lines by local anodic oxidation 36 2.5. Molecule beam epitaxy (MBE) of AlN nanoclucters on Si(111) 37 2.6. Microscopy and spectroscopy characterization methods of semiconductor and metal nanostructures at micro- and nanoscale 38 2.6.1. Micro- and nano-Raman, and Photoluminescence spectroscopies 38 2.6.2. Fourier transform infrared (FTIR) spectroscopy 39 2.6.3. Atomic Force Microscopy (AFM) 41 2.6.4. NeaSNOM platform for Nano-FTIR spectroscopy 43 2.7. Summary 45 3. Surface- enhanced Raman, PL and IR spectroscopies of hybrid semiconductor/metal nanostructures 46 3.1. SERS and SEPL of CdSe/CdS nanoplatelets on Au nanodisks 46 3.2. IR spectroscopy of hybrid semiconductor/metal nanostructures 52 3.2.1. Plasmon modes in gold nanoantennas on Si/SiO2 52 3.2.1.1. Plasmon modes in micro- and nanoantennas of various morphologies 57 3.2.1.2. Activation of even modes of localized surface plasmon in antennas 61 3.2.2. SEIRA of optical phonons in CdS, CdSe, PbS nanocrystals on Au micro- and nanoantennas 64 3.3. Summary 67 4. Nanoscopy of hybrid semiconductor/metal nanostructures 69 4.1. TERS of CdSe NCs on different plasmonic substrates 69 4.2. Gap-mode TERS imaging of CdSe NCs for different excitation energies 76 4.3. Gap-mode TERS imaging of CdSe/CdS nanoplatelets 79 4.4. Nano-FTIR Spectroscopy of SiOx nanowires 81 4.5. Plasmon-phonon nanoscale interaction in an Au nanoantenna on a thin SiO2 layer 85 4.6. Summary 87 5. Comparative nanoscale analysis of surface optical modes in AlN nanostructures 89 5.1. TERS mapping of a single AlN hexagonal nanocluster 89 5.2. Hyperspectral Nano-FTIR imaging of a single AlN hexagonal nanocluster 91 5.3. Polarized TERS mapping and Hyperspectral Nano-FTIR imaging of a single AlN nanowire 95 5.4. Summary 98 6. Summary 99 7. Appendix 101 8. Acknowledgements 104 9. Lebenslauf 105 10. Publications 106 11. Erklärung 108 12. Bibliography 109 13. List of Figures 125

Orientador: Ivo Alexandre Hummelgen / Dissertação(mestrado) - Universidade Federal do Parana

The increasing demand for nearline storage capacity in data centers calls for a continued enhancement in hard disk drive recording density far beyond one terabit per square inch. The thermal stability limit forces the drive manufacturers to develop new concepts in order to achieve this in the long term. Potential solutions are microwave-assisted magnetic recording (MAMR), heat-assisted magnetic recording (HAMR) and bit-patterned media (BPM). A simple example of BPM based on sputter-deposited Co/Pd multilayers and prepatterned substrates at hypothetical recording densities up to one terabit per square inch was studied by magnetic force microscopy (MFM). This system achieved promising results at lower densities, but an actual application for data storage, especially at one terabit per square inch and higher densities, requires elaborate optimizations. For some time now, FePt thin films have attracted much attention as prospective recording layers for high-density magnetic data storage due to their high magnetic anisotropy. The use of FePt films in HAMR is especially promising. This application has been tested successfully by Seagate and its key customers in recent years and is about to be introduced into the nearline hard disk drive market. It requires a tuning of the magnetic properties of FePt, especially of its Curie temperature. The addition of Cu proved to be effective in this regard and can also facilitate the formation of the crucial L10 structure and (001) texture during rapid thermal annealing of sputter-deposited thin films. Such films were prepared as bilayers of Cu and FePt on Si substrates, annealed for 30 s, and analyzed by X-ray diffraction (XRD) and SQUID vibrating sample magnetometry (SQUID-VSM). The influence of large Cu additions on important properties like lattice parameters, mosaicity, magnetic anisotropy and Curie temperature is discussed. The chemical long-range order was calculated from the XRD data, and a dedicated chapter of this thesis covers the most important factors to be considered in such calculations for textured thin films and other samples. The feasibility of creating patterned Fe-Cu-Pt films with perpendicular magnetic anisotropy, as needed for a combination of HAMR and BPM, by deposition through a PMMA mask, a lift-off process and subsequent annealing was investigated as well. The results indicate that the chosen approach might not lead to the required (001) texture when the nanostructures are small enough to compete with today's recording densities, so that either a continuous film might need to be etched after annealing or a seed layer might be required to induce the texture.:1. Motivation: Magnetic Data Storage 2. Experimental Techniques 3. Co/Pd Multilayers on Prepatterned Substrates 4. Fe-Pt and Fe-Cu-Pt Alloys 5. Rapid Thermal Annealing of FePt and FePt/Cu Films 6. Order Parameter Calculation 7. Summary