Dissertations / Theses on the topic 'Nanoscale properties'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Nanoscale properties.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Ferrari, Andrea Carlo. "Nanoscale properties of amorphous carbon." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621037.
Full textCao, Jingnan, and 曹靖楠. "Thermoelectric transport properties in nanoscale systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49799708.
Full textpublished_or_final_version
Physics
Master
Master of Philosophy
Afandi, Abdulkareem. "Electronic properties of doped-nanoscale diamonds." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10046056/.
Full textKrupskaya, Yulia. "Magnetic Properties of Molecular and Nanoscale Magnets." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-73289.
Full textEl, Aziz Youssef. "Novel hybrid nanoscale silsesquioxanes synthesis & properties." Thesis, Open University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528246.
Full textMönch, Tobias. "Exploring nanoscale properties of organic solar cells." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-189348.
Full textRaanaei, Hossein. "Tailoring Properties of Materials at the Nanoscale." Doctoral thesis, Uppsala : Uppsala University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-107425.
Full textMacias, Celia Edith 1982. "Nanoscale properties of poly(ethylene terephthalate) vascular grafts." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32727.
Full textIncludes bibliographical references (leaves 46-48).
Vascular grafts are prosthetic tubes that serve as artificial replacements for damaged blood vessels. Poly(ethylene-terephthalate), PET, has been successfully used in large diameter grafts; however, small caliber grafts are still a major challenge in biomaterials. Due to surface forces, blood plasma proteins adsorb to the graft, resulting in inflammation, infection, thrombus formation, and ultimately, vessel reclosure. The object of this project was to characterize and analyze the nanoscale surface properties of three different commercial vascular grafts, woven collagen-coated, knitted collagen- coated, and knitted heparin-bonded, all PET-based. The study was performed in order to ascertain differences in biocompatibility due to surface coating and morphology. Scanning Electron Microscopy, Atomic Force Microscopy and High Resolution Force Spectroscopy techniques were used to characterize the surface of the samples as well as to measure the forces between these surfaces and blood plasma proteins. The results will serve as a basis for the understanding of the nanoscale interactions between the biomaterial and blood plasma proteins. Such interactions are brought about by the different surface topologies and components, therefore a thorough understanding of surface properties will act as a building block for further changes in small caliber vascular grafts in order to enhance their biocompatibility.
by Celia Edith Macias.
S.B.
Minj, Albert <1986>. "Nanoscale-electrical and optical properties of iii-nitrides." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5193/.
Full textRossi, Robert C. Okumura Mitchio Lewis Nathan Saul. "The electrical properties of nanoscale parallel semiconductor interfaces /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-07132001-180811.
Full textKappiyoor, Ravi. "Mechanical Properties of Elastomeric Proteins." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54563.
Full textPh. D.
Han, Jixiong. "Processing microstructure evolution and properties of nanoscale aluminum alloy." Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1121701078.
Full textTitle from electronic thesis title page (viewed Apr. 11, 2006). Includes abstract. Keywords: Al-Cu nanoparticle; Al nanoparticle; Al-Al2O3 composite; 2024Al-Al2O3 composite; nanocomposite; nanoparticle; phase transformation; precipitate; plasma ablation; inert gas condensation; exploding wire; consolidation; sinter; cold roll; hot roll; aging; thermal-soaking; mechanical properties; strengthening mechanism. Includes bibliographical references.
Lei, Chunhong. "Nanoscale properties of conjugated polymers by scanning probe microscopy." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55924/.
Full textPrice, Tony S. "Nonlinear Properties of Nanoscale Barium Strontium Titanate Microwave Varactors." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4390.
Full textSalahshoor, Pirsoltan Hossein. "Nanoscale structure and mechanical properties of a Soft Material." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/924.
Full textChe, Rose Laili. "Exploiting nanoscale materials properties for controlled drug delivery systems." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/47950/.
Full textKöcher, Paul Tilman. "Nanoscale measurements of the mechanical properties of lipid bilayers." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:0b478b9f-70fc-436f-9803-5d3a203f0d7e.
Full textKatsamenis, Orestis L. "Bone matrix material properties on the micro- and nanoscale." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/352192/.
Full textHan, Jixiong. "Processing Microstructure Evolution and Properties of Nanoscale Aluminum Alloys." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1121701078.
Full textFarhana, Baset. "Micro/nano-scale Manipulation of Material Properties." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31862.
Full textParadinas, Aranjuelo Marcos. "Nanoscale properties of self-assembled and laterally nanostructured surface systems." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/294269.
Full textThe present work lies within the scope of the morphological, mechanical, electrostatic and conductive characterization of self-assembled and nanostructured systems, including organic thin films and inorganic surfaces. Scanning probe microscopy (SPM) techniques, in general, and scanning force microscopy (SFM), in particular has become one of the most powerful tools in nanotechnology because they offer the combined capability of surface properties characterization and manipulation of material surfaces in the nanoscale. In this work we make use of SPM techniques, both SFM and scanning tunneling microscopy (STM), under controlled ambient conditions for the characterization and manipulation of different self-assembled and nanostructured systems. We mainly focus on the use of SFM in contact, dynamic, friction force microscopy (FFM), conductive scanning force microscopy (CSFM) and Kelvin probe force microcopy (KPFM) operating modes for such a purpose. The thesis is organized in the following way: the motivations for this work are presented in chapter 1, and a short introduction to the self-assembled concept and nanostructured systems in organic thin films and inorganic surfaces is done in chapter 2. Chapter 3 introduces the fundamental description of the experimental techniques and procedures used. The main experimental characterization SPM techniques are introduced and a particular attention is devoted to explain the different SFM techniques used. In the same chapter, the growth techniques of organic thin film are explained, including, the solution based methods, the soft lithography μ-contact printing (μCP) and the organic molecular beam deposition (OMBD). In chapter 4 we investigate the influence of the supramolecular structure of self-assembled monolayers (SAMs) into the morphological, mechanical, electrostatic and conductive properties of a functionalized surface. For this purpose we study the CH3(C6H4)2(CH2)4SH) (BP4) molecule SAM on the Au(111) surface presenting two different coexisting supramolecular arrangements. We show how the supramolecular order of the SAM is a decisive factor influencing the nanoscale properties of the surface and also demonstrate how FFM can be employed to differentiate SAM domains with different orientation. In addition, based on electron current measurements, the combined use of STM and CSFM allows us interpreting the differences in apparent height as measured by one or the other technique in non-homogeneous organic layers. In chapter 5 we study the properties of the nanopatterned SrTiO3 (001) surface and explore its use as template for the selective adsorption of SAMs. We find that stearic acid molecules (containing a COOH headgroup) selectively chemisorb on the TiO2 surface. This fact allows us to investigate SAMs adsorption influence on the mechanical and electrostatic properties of this oxide surface. We address the main characteristics of the nanopatterned SrTiO3 (001) surface and we describe the selective adsorption of SAMs on the TiO2 surface, discussing how this influences the local mechanical and electrostatic properties of the surface. Finally, in chapter 6 we present two different tip-induced effects which can be use to manipulate organic thin film materials. We address the mechanical induced growth of pentacene molecular layers, a phenomena that can be used as a local nanolithography approach for nanostructuration. And we also provide a way for peeling a layered organic molecular material when a voltage is applied between the conducting system and the conducting probe of the SFM, which is important to take into account for the design of organic electronic devices.
Ong, Wee-Liat. "Thermal Properties of Organic-Inorganic Materials Superstructured at the Nanoscale." Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/500.
Full textMcKenna, Keith Patrick. "The simulation of the electronic transport properties of nanoscale devices." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421455.
Full textMurray, William Andrew. "Optical properties of nanoscale silver structures fabricated by nanosphere lithography." Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421567.
Full textChurch, Nathan Stewart. "Magnetic properties of iron-titanium oxides and their nanoscale intergrowths." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609524.
Full textGeist, Brian Lee. "Properties of Nanoscale Biomaterials for Cancer Detection and Other Applications." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27630.
Full textPh. D.
Palma, Matteo. "Supramolecular architectures on surfaces : self-organization and nanoscale electronic properties." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. http://www.theses.fr/2007STR13212.
Full textThe generation of multifunctional materials by self-assembly of specifically designed molecules, through supramolecular chemistry approaches, currently gathers a great interest in nanotechnology. In this context a great deal of effort has been devoted to achieve a full control of the self-organization of -conjugated molecules into highly ordered, anisotropic supramolecular architectures as spatially confined electrically active nano-objects. It is indeed well known that the order at the supramolecular level strongly affects the electronic properties of molecular based assemblies. In this thesis we report on the self-assembly on surfaces of different molecular systems into supramolecular nanostructures, as obtained by balancing the interplay of intramolecular, intermolecular, and interfacial interactions. On solid substrates structure, dynamics, electrical and electronic properties have been investigated on the nanometer scale making use primarily of Scanning Probe Microscopies, in particular Scanning Tunneling Microscopy and Scanning Force Microscopy (SFM) based approaches, such as Scanning Tunneling Spectroscopy (STS), Kelvin Probe Force Microscopy (KPFM) and Conducting Probe Force Microscopy (C-AFM). The nanostructures that have been developed are not only of interest as nano-constructions on solid surfaces, but exhibit properties that make them candidates for applications in the field of (supra)molecular electronics. In order to explore the use of weak interactions to for functional supramolecular assemblies at surfaces, we have studied the following systems:i)an alkylated thio-triphenylene compound known to from a discotic liquid crystal phase through stacking, with potentially interesting electronic properties;ii)an amide functionalized hexaazatriphenylene, of interest as potential electron carrier in view of the nature of its conjugated core, and forming a discotic liquid crystal phase through the formation of Hydrogen bonds between amide units;iii)a HBC-PeryleneMonoImide dyad, as a single molecule Donor-Acceptor system;iv) HBC-nucleotide functionalized compounds, to exploit directionality and recognition properties of hydrogen bonds between nucleotides;v)Cavitand compounds as molecular building blocks for host-guest assemblies with controlled curvature. Among triphenylene derivatives, we have centered our attention, in collaboration with the group of Prof. Yves Geerts of the Université Libre de Bruxelles (Belgium), on hexaazatriphenylenes, and on an alkylated thio-triphenylene compound. This latter discotic is a liquid crystal forming molecule holding interesting electronic properties. We followed its self-organization at the solid-liquid interface observing a packing into monolayers bearing two coexisting structural motifs on the basal plane of graphite. The temporal evolution of domain boundaries in a polycrystalline monolayer, explored by recording series of subsequent STM images, revealed an Ostwald ripening phenomenon, i. E. Coarsening in two-dimensional molecular polycrystals. The electrical properties have been investigated at both the single molecule level, using STS, and at the ensemble (supramolecular) level by means of C-AFM. On the other hand SFM microscopy experiments highlighted the formation of edge-on nanowires on the surface of electrically insulating substrates, such as muscovite mica and SiOx. Approaches have been explored to drive the self-assembly of the aforementioned nano-wires embedded in the gap between nano- electrodes, and to study their electrical behavior in such a configuration. In a different way, hexathialkylhexaazatriphenylenes do not form columnar liquid crystalline phases like the corresponding triphenylene derivatives, probably due to the large negative charges on the nitrogen atoms that lead to a repulsion of adjacent cores. Hydrogen bonds between peripheral amide units have been therefore used to counterbalance and overcome this Coulombic repulsion. We have studied the self-organization and electronic properties of a specially designed and synthesized azatriphenylene. Such studies revealed in different environments the formation of columnar architectures, where the single molecular discs are held together by H-bonds between amide moieties. In particular a network of fibers was formed, exhibiting a height comparable to the molecular diameter. The electronic properties both at the single molecule as well as at the ensemble level have been investigated. On electrically conductive substrates such as highly oriented pyrolitic graphite (HOPG), STM investigations at the solid-liquid interface highlighted the formation of ordered monolayers and the analysis of the energy levels contributing to the contrast in the current STM images, supported by quantum-chemical calculations (pursued in collaboration with the group of Dr. Jérôme Cornil of the Université de Mons (Belgium)), revealed a significant contribution of the electronic levels localized on the amide groups. Furthermore KPFM measurements allowed us to determine the surface potential of the self-organized layers. In collaboration with the group of Prof. Klaus Müllen of the MPI of Maintz (Germany), we have studied various HBC-derivatives. Exploiting the directionality and recognition properties of hydrogen bonds between nucleotides, branched architectures have been obtained from hybrid solutions of HBC-nucleotide functionalized compounds on both insulating (mica and SiOx) and conductive (HOPG) surfaces, employing different room temperature deposition methods. Furthermore through combined STM and SFM studies we have investigated the behaviour of a HBC-PeryleneMonoImide dyad on HOPG at the solid liquid interface, and on dry films, as a single molecule Donor-Acceptor system. In addition, in collaboration with the group of Prof. Enrico Dalcanale at the University of Parma (Italy), we have extended our studies of self assembly on surfaces to cavitand compounds as system that can from, through host-guest recognition, supramolecular polymers with controlled curvature. Cavitands are indeed versatile molecular building blocks for host-guest assemblies. The design, crystal structure determination and self-assembly in solution and on surfaces of supramolecular polymers from cavitand based compounds have been subject of investigation. Studies in solution provided evidence for the formation of polymers from specifically designed cavitands, and the aggregation behavior was quantified. The successful translation of the given self-assembly procedure from solution to surfaces required a comprehensive understanding and control over various boundary conditions. Rod-like architectures have been in this way visualized on surface. A bending in two dimensions of the single rods has also been observed and it has been correlated to the degree of curvature of the polymer as obtained form simulation studies. In summary, we have studied the self organization of a variety of molecular systems into supramolecular architectures on surfaces, exploring structural, electrical and electronic properties down to the nanoscale. Triphenylene based compounds have proved to exhibit properties that make them interesting for potential applications as quasi-1D charge carrier systems for electrical conduction. Moreover, we have shown how nucleoside recognition can be exploited to drive the self-assembly of HBCs from solution to surfaces. In addition cavitand compounds have shown to be versatile molecular building blocks to form polymers with potentially controlled curvature
Ditzler, Lindsay Rachel. "Probing physical properties at the nanoscale using atomic force microscopy." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3445.
Full textRiedel, Clément. "Dielectric and mechanical properties of polymers at macro and nanoscale." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20073.
Full textThe aim of this thesis was first to understand the physical theories that describe the dynamics of linear polymers at the macroscopic scale. Rouse and the reptational tube theory describe the large scale dynamics of unentangled and entangled polymers respectively. Using Broadband Dielectric Spectroscopy (BDS) and rheology we have studied the different transition between these two regimes. Effects of entanglement on dielectric spectra will be discussed (Rheologica Acta. 49(5):507-512). Avoiding the segmental relaxation contribution and introducing a distribution in the molecular weight we have been able to perform a comparison of the Rouse model with experiment dielectric and rheological data (Macromolecules 42(21): 8492-8499) Then we have developed EFM-based methods in order to study the local dynamics. Using the numerical simulation of the Equivalent Charge Method, the value of the static dielectric permittivity has been quantified from the measurement of the force gradient created by a VDC potential between a tip and a grounded dielectric (Journal of Applied Physics 106(2):024315). This method allows a quantitative mapping of dielectric properties with a 40 nm spatial resolution and is therefore suitable for the study of nano-defined domains (Physical Review E 81(1): 010801). The electrical phase lags in the 2ω components of the force or force gradient created by VAC voltage, ΔΦ2ω, are related with dielectric losses. Measuring the frequency dependence of ΔΦ2ω Crieder et al (Applied Physics Letters 91(1):013102) have shown that the dynamics at the near free surface of polymer films is faster than the one in bulk. We have used this method in order to visualize the activation of the segmental relaxation with temperature and frequency (Applied Physics Letters 96(21): 213110). All this measurements can be achieved using standard Atomic Force Microscope (and a lock-in) for VAC measurements
Balakrishnan, Nilanthy. "Novel approaches to the fabrication of nanoscale devices." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/50598/.
Full textZhou, Xiang Ph D. Massachusetts Institute of Technology. "IIl-nitride nanowires and heterostructures : growth and optical properties on nanoscale." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/89962.
Full textCataloged from PDF version of thesis. "June 2014."
Includes bibliographical references (pages 172-194).
Gallium nitride (GaN) and indium gallium nitride (InGaN) nanowires promise potential for further improving the electricity-to-light energy conversion efficiencies in light emitting diodes due to strain relaxation, reduced density of structural defects, and easier light extraction. Material quality and effective band engineering of such III-nitride nanowires are crucial for the design and fabrication of their optoelectronic applications such as LEDs, lasers and photodetectors. In this thesis, we first demonstrate effective control over GaN nanowire size, growth rate and structural quality through careful choice of metal seed particles. The differences in morphology, structural defects and optical properties of GaN nanowires grown by metalorganic chemical vapor deposition were studied systematically by electron microscopy and photoluminescence, and related to supersaturation in different seed particles and nanowire nucleation mechanisms. These results also demonstrate that systematic screening of seed materials is essential for synthesizing nanostructures with defect-free structures and other functional heterostructures. Next, challenges for nanoscale mapping of band engineering were successfully addressed through direct spatial correlation of optical properties to a variety of III-nitride heterostructures grown by molecular beam epitaxy, including GaN p-n junction nanorods, InGaN nanodisks, and GaN quantum disks and quantum wires. We demonstrate that effective doping, alloying and quantum confinement can be readily achieved in nanowire heterostructures, by cathodoluminescence in scanning transmission electron microscopy. P-n junction position and carrier diffusion lengths inside a single GaN nanorod were determined with nanometer spatial resolution. InGaN disk compositional uniformities were quantified from their optical emissions, which revealed substantial compositional inhomogeneity in bottom-up synthesized nanostructures. The studies on optical properties of individual GaN quantum structures demonstrated that small differences in the degree of quantum confinements resulted in substantial changes in the optical band gap. More importantly, reduced light emissions are directly correlated to regions containing grain boundaries, dislocations and stacking faults, which were formed as a result of nanorod coalescence and fluctuations in growth environment during nanostructure synthesis. Our findings demonstrate that controlling compositional and structural homogeneity, understanding defect formation mechanism and their effects on materials properties are key challenges to be addressed for developing large scale functional devices based on bottom-up synthesized nanostructured materials.
by Xiang Zhou.
Ph. D.
Savisalo, Tuukka S. "Enhancing the tribological properties of CrN/NbN nanoscale multilayer PVD coatings." Thesis, Sheffield Hallam University, 2008. http://shura.shu.ac.uk/20329/.
Full textPark, Jeongwon. "Electronic properties of organic thin film transistors with nanoscale tapered electrodes." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3316420.
Full textTitle from first page of PDF file (viewed September 4, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 77-82).
El, Safty Samy. "Elastic and viscoelastic properties of resin composites at the macroscopic and nano scales." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/elastic-and-viscoelastic-properties-of-resin-composites-at-the-macroscopic-and-nano-scales(8a9ade8e-7417-475c-a4ba-71b4990fa2b8).html.
Full textKolpakov, A. Y., A. I. Poplavsky, M. E. Galkina, M. G. Kovaleva, I. V. Sudzhanskaya, and J. V. Gerus. "Properties of Nanoscale Carbon Coatings Obtained by the Pulsed Vacuum-Arc Method on Silicon." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35305.
Full textSingh, Lovejeet. "Effect of Nanoscale Confinement on the Physical Properties of Polymer Thin Films." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4822.
Full textFu, Ceji. "Radiative Properties of Emerging Materials and Radiation Heat Transfer at the Nanoscale." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4941.
Full textTam, Enrico. "Characterization and modification of the mechanical and surface properties at the nanoscale." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210226.
Full textand surface properties at the nano-scale in order to conceive reliable N/MEMS
(Nano and Micro ElectroMechanical Systems) applications. Techniques like nanoindentation,
nanoscratching, atomic force microscopy have become widely used to measure
the mechanical and surface properties of materials at sub-micro or nano scale. Nevertheless,
many phenomena such us pile-up and pop-in as well as surface anomalies
and roughness play an important role in the accurate determination of the materials
properties. The first goal of this report is to study the infulence of these sources of data
distortion on the experimental data. The results are discussed in the first experimental
chapter.
On the other hand, conceptors would like to adapt/tune the mechanical and surface
properties as a function of the required application so as to adapt them to the industrial
need. Coatings are usually applied to materials to enhance performances and reliability
such as better hardness and elastic modulus, chemical resistance and wear resistance.
In this work, the magnetron sputtering technique is used to deposit biocompatible thin
layers of different compositions (titanium carbide, titanium nitride and amorphous
carbon) over a titanium substrate. The goal of this second experimental part is the
study of the deposition parameters influence on the resulting mechanical and surface
properties.
New materials such as nanocrystal superlattices have recently received considerable
attention due to their versatile electronic and optical properties. However, this new
class of material requires robust mechanical properties to be useful for technological
applications. In the third and last experimental chapter, nanoindentation and atomic
force microscopy are used to characterize the mechanical behavior of well ordered lead
sulfide (PbS) nanocrystal superlattices. The goal of this last chapter is the understanding
of the deformation process in order to conceive more reliable nanocrystal
superlattices.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Rodriguez, Brian Joseph. "NANOSCALE INVESTIGATION OF THE PIEZOELECTRIC PROPERTIES OF PEROVSKITE FERROELECTRICS AND III-NITRIDES." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-10072003-122453/.
Full textRagazzon, Davide. "Titania Nanoscale Films and Surfaces : Surface Science Investigation of Structure and Properties." Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-224124.
Full textMoro, Daniele <1979>. "Nanoscale surface properties and interaction with fundamental biomolecules of chlorite and phlogopite." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6352/.
Full textAnand, Kanika. "Surface properties of complex intermetallics at the nanoscale : from fundamentals to applications." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0239/document.
Full textComplex metallic alloys (CMAs) are intermetallic compounds possessing a large unit cell containing several tens to hundreds of atoms. Their structure can be described alternatively by the packing of highly symmetric atomic clusters. Clathrate (or cage) compounds are a new class of CMAs having a crystal structure described by a complex arrangement of covalently-bonded cages. The Ba8Au5.25Ge40.75 type-I clathrate is one such cage compound, whose bulk properties have been (and still are) extensively explored for thermoelectric applications. In fact, it is possible to tune the compound electronic structure by a fine control of its bulk composition. Regarding the properties of the Ba8Au5.25Ge40.75 surface, information remains scarce if not inexistent. However, it is known that the surfaces of CMAs often exhibit interesting surface properties. To this end, we have studied two low-index surfaces: BaAuGe(100) and BaAuGe(110) by a combination of experimental (XPS; LEED; STM) and computational (DFT) methods. Experimental results show no evidence for surface segregation and LEED patterns are consistent with (1x1) bulk terminations with no surface reconstruction. The interplay between the 3D nano-caged structure and 2D surfaces is investigated. We demonstrate that the surface structures of the two surfaces considered preserve the bulk structure cages in addition to an ordered arrangement of surface Ba atoms. The two surfaces are formed by a breakage of highly directional covalent bonds present within the framework, hence leading to destabilizing dangling bonds. Ab initio calculations show that the surface structure is stabilized through electron charge transfer from protruding Ba to surface Ge and Au atoms, saturating the dangling bonds. This charge-balance mechanism lifts the possible surface reconstruction envisaged. We reveal how the surface nanostructuration is surface orientation dependent. The results indicate that the surface electronic structure of BaAuGe(110) is impacted by the Au surface concentration. The surface models for BaAuGe(100) and BaAuGe(110) present a metallic character and low work function values, useful for further applications. Such structurally complex surfaces may also be used as templates for novel nanoscale architectures. Further in this work, we also applied the state-of-the-art surface science techniques to investigate the wetting properties of Al-based CMAs. In these experiments, chemically inert Pb element was used as a metal probe. Systematic analysis is done to find the correlation between the wetting properties and the electronic structure properties of these CMAs. Interfacial energy calculations have been performed to model the Pb/CMA interface based on few approaches reported in literature. We have tested these approaches on a moiré patterned Pb(111)/Al(111) interface. This interface is found to be controlled by geometric factors. Hence, an acquired understanding was applied to Pb deposited on Al13Co4(100) (Al-rich side) interface
Sheng, Nuo 1977. "Micro/nanoscale modeling of anisotropic mechanical properties of polymer/layered-silicate nanocomposites." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/28257.
Full textIncludes bibliographical references (leaves 123-125).
Polymer nano-clay composites have been observed to exhibit dramatic enhancements in mechanical properties with relatively low filler loadings (1-4 percent volume fraction). These property enhancements have been speculated to be a result of the change in polymer morphology and properties within the polymer/particle interfacial regions, due to the nanometer length scale and the large interface area/unit volume of the nanoparticles. In this work, the potential contribution of composite-level effects on the observed enhancements is explored. Two-dimensional models of various representative volume elements (RVEs) of the underlying structure of the polymer nano-clay composite are constructed. These models are characterized by clay particle volume fraction and micro/nano scale morphological features such as clay particle aspect ratio (length/thickness, L/t), clay particle distribution (random vs. regular patterns) and clay particle orientation distribution. Macroscopic moduli of these RVEs are predicted as a function of these geometrical parameters as well as particle and matrix stiffness parameters through FEM simulations. Effective properties of intercalated clay particles have been estimated in terms of characteristic clay structural parameters (interlayer spacing and number of layers), with additional information from molecular dynamics simulations of silicate layer stiffness. The predictions of macroscopic stiffness from these two-dimensional micromechanical models, based on structure-dependent particle volume fraction and properties, are consistent with experimental observations. Furthermore, studies of the local stress/strain fields show that the stiffness enhancement comes through the efficient load transfer mechanism in the high aspect ratio fillers, modulated by the strain shielding effect in the matrix. These results suggest that physically-based composite level interpretations may explain the stiffness enhancement mechanism of polymer nanocomposites to a large degree. The adopted methodology offers promise for study of related properties in polymer/layered-silicate nanocomposites.
by Nuo Sheng.
S.M.
Eliason, Jeffrey Kristian. "Optical transient grating measurements of micro/nanoscale thermal transport and mechanical properties." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98819.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 109-119).
The laser-based transient grating technique was used to study phonon mediated thermal transport in bulk and nanostructured semiconductors and surface wave propagation in a monolayer of micron sized spheres. In the transient grating technique two picosecond pulses are crossed to generate a spatially periodic intensity profile. The spatially periodic profile generates a material excitation with a well-defined wave vector. The time dependence of the spatially periodic material response is measured by monitoring the diffracted signal of an incident probe beam. Non-diffusive thermal transport was observed in thin Si membranes as well as bulk GaAs at relatively short (micron) transient grating periods. First-principles calculations of the phonon mean free paths in Si and GaAs were compared with experimental results and showed good agreement. Preliminary measurements on promising thermoelectric materials such as PbTe and Bi2Te3 are presented showing evidence of non-diffusive transport at short length scales. The transient grating technique was used to measure the thermal conductivity of Si membranes with thickness ranging from 15 nm to 1518 nm. Using the Fuchs-Sondheimer suppression function along with first-principles results, the thermal conductivity as a function of membrane thickness was calculated. The calculations showed excellent agreement with experimental measurements. A convex optimization algorithm was employed to reconstruct the phonon mean free path distribution from experimental measurements. This marks the first experimental determination of the mean free path distribution for a bulk material. Thermal conductivity measurements at low temperatures in a 200 nm Si membrane indicate the breakdown of the diffuse boundary scattering approximation. The transient grating technique was used to generate surface acoustic waves and measure their dispersion in a monolayer of 0.5 - 1 [mu]m diameter silica spheres. The measured dispersion curves show "avoided crossing" behavior due to the interaction between an axial contact resonance of the microspheres and the surface acoustic wave at a frequency of -200MHz for the 1 [mu]m spheres and -700 MHz for the 0.5 [m spheres. The experimental measurements were fit with an analytical model in which the contact stiffness was the only fitting parameter. Preliminary results of surface acoustic wave propagation in microsphere waveguides, transmission through a microsphere strip, and evidence of a nonlinear response in a 2D array of microspheres are presented.
by Jeffrey Kristian Eliason.
Ph. D.
Eriksson, Martin. "Nanoscale electrical properties of heterojunction interfaces for solar cells : modeling and experiments." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72505.
Full textChaudhari, Abhijeet Kishor. "Nanoscale engineering of guest@host metal-organic framework materials for optoelectronic properties." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:ea6499f2-f4b8-4c32-926b-1713b96e487a.
Full textZhao, Zhibo Ph D. Massachusetts Institute of Technology. "Nanoscale optoelectronic properties in traditional and emerging materials for light-emitting diodes." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121609.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 137-159).
Although InGaN/GaN-based quantum well (QW) heterostructures continue to set the industry standard for inorganic blue and green light emitting diodes (LEDs), these devices suffer from efficiency droop at high current densities and material quality degradation at longer emission wavelengths. Establishing rational process design principles to address such issues remains inhibited by ongoing controversy surrounding the impact of commonly observed defects such as well-width fluctuations or V-pit defects on carrier recombination. Organic-inorganic perovskites have begun to attract attention as a potential next-generation LED material, but these nascent materials suffer from rapid material degradation under device operating conditions. Understanding structure-property correlations will be necessary to improve incumbent InGaN/GaN technologies and evaluate the potential of organic-inorganic perovskites.
In InGaN/GaN QW heterostructures, we first employ aberration-corrected scanning transmission electron microscopy (STEM) to examine the impact of well-width fluctuations and QW period on measured EQE and find no significant correlation. Next, we observe time-delayed cathodoluminescence (CL) rise dynamics in droop-mitigating QW designs and propose a model linking rise behavior to carrier transport and deep level defects. Finally, we use CL-STEM to map radiative recombination around commonly observed V-pit defects with nanoscale spatial and spectral resolution. Furthermore, dark field diffraction contrast imaging elucidates the relationship between V-pit optical emission and threading dislocation character. These results provide a platform for evaluating the impacts of microstructural defects on LED device performance. In methylammonium lead iodide, we use STEM imaging to establish a direct correlation between local stoichiometry and CL intensity.
We demonstrate that areas of high CL intensity correspond to regions which are enriched in iodide content relative to lead. Furthermore, CL-STEM imaging reveals the presence of localized high-energy emissions which we attribute to beam-induced ion migration. The continuous evolution of such high-energy emissions under electron beam irradiation suggests these local spectral heterogeneities could reflect material evolution during device degradation.In summary, the current work demonstrates novel insights gained by the application of advanced electron imaging techniques to two vastly different materials systems. Our findings suggest that continued improvements in process design will hinge on controlling the distribution of structural defects in order to minimize undesirable recombination pathways.
by Zhibo Zhao.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
Rupasinghe, R.-A. Thilini Perera. "Probing electrical and mechanical properties of nanoscale materials using atomic force microscopy." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/2268.
Full textZhang, Yihuai. "Microstructure and Nanoscale Rock Mechanical Properties of Coal: Applications to CO2 Storage." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/65384.
Full textOsaka, Miki. "Nanoscale Electronic Properties of Conjugated Polymer Films Studied by Conductive Atomic Force Microscopy." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225631.
Full text