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Plasmonic lightning-rod effect
Řepa, Rostislav ; Konečná, Andrea (referee) ; Křápek, Vlastimil (advisor)
This bachelor thesis deals with an experimental and theoretical research of the plasmonic lightning-rod effect. Electron energy loss spectroscopy has been used to investigate the electromagnetic response of plasmonic antennas and to study the impact of the curvature of their surfaces on the local enhancement of an electromagnetic field. A theoretical background based on interactions of the electromagnetic field and free electrons in metals is provided in the first chapter. Next, experimental and theoretical methods including the fabrication process of plasmonic antennas and inicialization of simulations are introduced. Observed resonances of localised surface plasmons are characterised in the spectral region and their mapping is performed. The calculated loss spectra are compared with the experimental loss spectra and the field enhancemnet due to the curvature of plasmonic antennas is evaluated.
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Imaging the magnetic field of plasmonic antennas based on Babinet's principle
Špičáková, Tereza ; Horák, Michal (referee) ; Křápek, Vlastimil (advisor)
This thesis concerns plasmonic antennas and the electromagnetic field of surface plasmon polaritons. In the first chapter we look at the theory of the electromagnetic field and the electromagnetic wave associated with the interface between metals and dielectric materials and we explain Babinet’s principle. In the next part of the thesis we describe the process of fabrication of plasmonic antennas using Kaufman ion source and focused ion beam. We continue wuth the theoretical description of the electron energy loss spectroscopy and the application of this method for characterizing the optical response of these structures. In the last part we introduce the principles of processing the measured data and the conclusions drawen frome this data. Next we will analyze the limits of the validity of Babinet’s principle and using this principle, we will image the magnetic field of the antennas. Finally, we discuss the possibilities of describing this problem with computer simulation.
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Modelling electron energy-loss spectra of vanadium dioxide nanostructures
Kabát, Jiří ; Křápek, Vlastimil (referee) ; Konečná, Andrea (advisor)
This thesis concerns the characterization of optical modes in vanadium dioxide (VO2) nanostructures, mainly by simulating numerically electron energy loss spectroscopy (EELS) intensity. Among the studied optical modes, there are plasmons, phonons and Mie-type resonances, for which we performed a literature review. VO2 undergoes a phase transition when reaching a temperature of about 67 °C from the insulating phase to the metallic phase. This phase transition is connected to significant changes in optical properties, which offer potential uses in nanophotonics. The main part of the thesis is devoted to numerical simulations, which were firstly performed for thin VO2 slabs and then for VO2 nanoparticles. In simulations of VO2 nanoparticles in the metallic phase, we observed electron energy losses caused by plasmons and localized surface plasmons, which were then characterized and imaged by spacedependent EELS maps. In nanoparticles in the insulating phase, losses caused by phonon excitations and material absorption were observed. A new kind of loss contribution was observed for some geometries, potentially related to the Mie-type resonances.
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Optical dichroism in vortex electron energy-loss spectroscopy
Ošmera, Martin ; Dub, Petr (referee) ; Konečná, Andrea (advisor)
Vortexové elektronové svazky (VES) nesou orbitální moment hybnosti a při jejich interakci s chirálními strukturami lze pozorovat dichroismus. Ve spektroskopii energiových ztrát elektronů získáme použitím levotočivých VES jiná spekta, než v případě pravotočivých. Tohoto jevu lze využít například v analýze chirálních molekul nebo nanostruktur. Předkládáme semianalytický plně retardovaný model interakce nefokusovaného VES s bodovou chirální polarizovatelnou částicí a numerický kvazistatický model interakce nefokusovaného VES s chirální ,,makroskopickou`` nanostrukturou.
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Interaction of metallic nanoparticles and fast electrons
Konečná, Andrea ; Tyc, Tomáš (referee) ; Dub, Petr (advisor)
Scanning transmission electron microscopy is one of the essential techniques suitable not only for imaging of nanostructures, but also for various kinds of spectroscopy and, as it was recently demonstrated, nanomanipulation. In this thesis, we deal with an interaction of fast electrons and metallic spherical nanoparticles, specifically aluminium and gold nanospheres. First, we present both analytical and numerical calculations of electron energy loss spectra and their analysis for different parameters. The main part of the thesis is devoted to theoretical calculations of forces acting on the nanosphere due to the electron passing in its close proximity. Based on our novel results revealing a time evolution of the mechanical force, we also propose a possible mechanism responsible for the nanoparticle movement in electron microscopes.
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Plasmonic lightning-rod effect
Řepa, Rostislav ; Konečná, Andrea (referee) ; Křápek, Vlastimil (advisor)
This bachelor thesis deals with an experimental and theoretical research of the plasmonic lightning-rod effect. Electron energy loss spectroscopy has been used to investigate the electromagnetic response of plasmonic antennas and to study the impact of the curvature of their surfaces on the local enhancement of an electromagnetic field. A theoretical background based on interactions of the electromagnetic field and free electrons in metals is provided in the first chapter. Next, experimental and theoretical methods including the fabrication process of plasmonic antennas and inicialization of simulations are introduced. Observed resonances of localised surface plasmons are characterised in the spectral region and their mapping is performed. The calculated loss spectra are compared with the experimental loss spectra and the field enhancemnet due to the curvature of plasmonic antennas is evaluated.
|
|
|
Optical dichroism in vortex electron energy-loss spectroscopy
Ošmera, Martin ; Dub, Petr (referee) ; Konečná, Andrea (advisor)
Vortexové elektronové svazky (VES) nesou orbitální moment hybnosti a při jejich interakci s chirálními strukturami lze pozorovat dichroismus. Ve spektroskopii energiových ztrát elektronů získáme použitím levotočivých VES jiná spekta, než v případě pravotočivých. Tohoto jevu lze využít například v analýze chirálních molekul nebo nanostruktur. Předkládáme semianalytický plně retardovaný model interakce nefokusovaného VES s bodovou chirální polarizovatelnou částicí a numerický kvazistatický model interakce nefokusovaného VES s chirální ,,makroskopickou`` nanostrukturou.
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Modelling electron energy-loss spectra of vanadium dioxide nanostructures
Kabát, Jiří ; Křápek, Vlastimil (referee) ; Konečná, Andrea (advisor)
This thesis concerns the characterization of optical modes in vanadium dioxide (VO2) nanostructures, mainly by simulating numerically electron energy loss spectroscopy (EELS) intensity. Among the studied optical modes, there are plasmons, phonons and Mie-type resonances, for which we performed a literature review. VO2 undergoes a phase transition when reaching a temperature of about 67 °C from the insulating phase to the metallic phase. This phase transition is connected to significant changes in optical properties, which offer potential uses in nanophotonics. The main part of the thesis is devoted to numerical simulations, which were firstly performed for thin VO2 slabs and then for VO2 nanoparticles. In simulations of VO2 nanoparticles in the metallic phase, we observed electron energy losses caused by plasmons and localized surface plasmons, which were then characterized and imaged by spacedependent EELS maps. In nanoparticles in the insulating phase, losses caused by phonon excitations and material absorption were observed. A new kind of loss contribution was observed for some geometries, potentially related to the Mie-type resonances.
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|
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Imaging the magnetic field of plasmonic antennas based on Babinet's principle
Špičáková, Tereza ; Horák, Michal (referee) ; Křápek, Vlastimil (advisor)
This thesis concerns plasmonic antennas and the electromagnetic field of surface plasmon polaritons. In the first chapter we look at the theory of the electromagnetic field and the electromagnetic wave associated with the interface between metals and dielectric materials and we explain Babinet’s principle. In the next part of the thesis we describe the process of fabrication of plasmonic antennas using Kaufman ion source and focused ion beam. We continue wuth the theoretical description of the electron energy loss spectroscopy and the application of this method for characterizing the optical response of these structures. In the last part we introduce the principles of processing the measured data and the conclusions drawen frome this data. Next we will analyze the limits of the validity of Babinet’s principle and using this principle, we will image the magnetic field of the antennas. Finally, we discuss the possibilities of describing this problem with computer simulation.
|
|
|
Interaction of metallic nanoparticles and fast electrons
Konečná, Andrea ; Tyc, Tomáš (referee) ; Dub, Petr (advisor)
Scanning transmission electron microscopy is one of the essential techniques suitable not only for imaging of nanostructures, but also for various kinds of spectroscopy and, as it was recently demonstrated, nanomanipulation. In this thesis, we deal with an interaction of fast electrons and metallic spherical nanoparticles, specifically aluminium and gold nanospheres. First, we present both analytical and numerical calculations of electron energy loss spectra and their analysis for different parameters. The main part of the thesis is devoted to theoretical calculations of forces acting on the nanosphere due to the electron passing in its close proximity. Based on our novel results revealing a time evolution of the mechanical force, we also propose a possible mechanism responsible for the nanoparticle movement in electron microscopes.
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