|
|
Fabrication, optimization and in-situ characterization of thermally tunable vanadium dioxide nanostructures
Krpenský, Jan ; Maniš, Jaroslav (oponent) ; Konečná, Andrea (vedoucí práce)
Vanadium dioxide (VO2) has attracted increasing attention over the past decades due to its metal-insulator phase transition at temperature around 68 °C. This phase change is accompanied by lattice change from monoclinic (dielectric) to tetragonal (metal), lattice shrinking in the metallic state, and stark difference in the infrared transmittance between both phases. However, fabrication of VO2 thin films can be challenging due to other possible stoichiometric configurations, such as VO, V2O3, or V2O5. Many fabrication techniques have been used in recent years, where optimized fabrication process produces VxOy in the desired stoichiometry of VO2. In this Thesis, a summary of three deposition techniques suitable for the deposition of VO2 thin films is made and the process of creating thin samples (lamellae) suitable for study in the transmission electron microscopy (TEM) via focused ion beam (FIB) is described. Utilizing TEM with in-situ heating for characterization of VO2 samples produces valuable information on the microstructure of VO2 both below and above the transition temperature. In addition, electron energy-loss spectroscopy gives precious insight into the changing of different stoichiometries of VO2 in correlation to the thickness of the examined sample, near the sample edge in particular.
|
|
|
Charakterizace optických vlastností InAs nanodrátů
Hošková, Michaela ; Ligmajer, Filip (oponent) ; Musálek, Tomáš (vedoucí práce)
Bakalářská práce je zaměřena na přípravu InAs nanodrátů a jejich následnou optickou charakterizaci. K přípravě nanodrátů je využita výhradně fyzikální depozice z plynné fáze pomocí metody selektivní epitaxe v aparatuře MBE. Jsou optimalizovány růstové podmínky pro tvorbu nanodrátů a jejich rozměry jsou charakterizovány rastrovacím elektronovým mikroskopem. S pomocí konfokální spektroskopie a spektroskopie ztrát energie elektronů je měřena optická odezva a studován vliv geometrie jednotlivých nanodrátů. Motivací je vývoj nové optické metody monitorující nanodráty přímo při růstu v aparatuře MBE.
|
|
|
Electron microscopy and spectroscopy in plasmonics
Horák, Michal ; Krenn, Joachim (oponent) ; Shegai, Timur (oponent) ; Šikola, Tomáš (vedoucí práce)
This thesis deals with electron and ion beam techniques for fabrication and characterization of plasmonic nanostructures. Analytical electron microscopy focusing on applications in the field of plasmonics is discussed. The emphasis is given to electron energy loss spectroscopy (EELS) and cathodoluminescence. Further, fabrication of plasmonic samples for transmission electron microscopy is introduced while the aim is put at focused ion beam lithography and at sample preparation using chemically synthesized particles in water solution. The main research results are divided into four parts. The first part covers a comparative study of plasmonic antennas fabricated by electron beam and focused ion beam lithography. While both techniques are suitable for the fabrication of plasmonic antennas, electron beam lithography shall be prioritized over focused ion beam lithography due to better quality of the resulting antennas and considerably stronger plasmonic response in EELS. Antennas fabricated by focused ion beam lithography have slightly dull edges, exhibit pronounced thickness fluctuation, and they are also strongly contaminated not only by organic contaminants, but also by residues of FIB milling including implanted milling ions and atoms of a titanium adhesion layer. In the second part, Babinet's principle of complementarity for plasmonic nanostructures is investigated on a set of gold disc-shaped antennas and complementary apertures in a gold layer with various diameters. The complementarity is confirmed for fundamental plasmon properties such as resonance energies, but differences rising from the limited validity of Babinet's principle are found, for example, for the spatial distribution of the near-field of plasmon polaritons. The third part summarizes a study of nanostructures with functional properties related to the local enhancement of electric and magnetic field. Bow-tie and diabolo plasmonic antennas, both in the form of particles and in the form of apertures, exhibit particularly strong local field enhancement. Our study identifies several modes of localized surface plasmons in these antennas and characterizes their properties including mode energy, near field electric and magnetic field distribution, and the qualitative distribution of charge nodes and current associated with electron gas oscillations. Next, we have studied mode energy tunability in near infrared and visible spectral regions and focused on Babinet's complementarity between direct and inverted antennas. The last part is focused on silver amalgam, which is a novel and very prospective plasmonic material. By changing the size of silver amalgam nanostructures their plasmon resonance can be tuned from ultraviolet through the whole visible to infrared region. As silver amalgam is well investigated in the field of electrochemistry, silver amalgam nanoparticles opens a possibility to combine plasmonics and electrochemistry together.
|
|
| |
|
|
Charakterizace optických vlastností InAs nanodrátů
Hošková, Michaela ; Ligmajer, Filip (oponent) ; Musálek, Tomáš (vedoucí práce)
Bakalářská práce je zaměřena na přípravu InAs nanodrátů a jejich následnou optickou charakterizaci. K přípravě nanodrátů je využita výhradně fyzikální depozice z plynné fáze pomocí metody selektivní epitaxe v aparatuře MBE. Jsou optimalizovány růstové podmínky pro tvorbu nanodrátů a jejich rozměry jsou charakterizovány rastrovacím elektronovým mikroskopem. S pomocí konfokální spektroskopie a spektroskopie ztrát energie elektronů je měřena optická odezva a studován vliv geometrie jednotlivých nanodrátů. Motivací je vývoj nové optické metody monitorující nanodráty přímo při růstu v aparatuře MBE.
|
|
|
Fabrication, optimization and in-situ characterization of thermally tunable vanadium dioxide nanostructures
Krpenský, Jan ; Maniš, Jaroslav (oponent) ; Konečná, Andrea (vedoucí práce)
Vanadium dioxide (VO2) has attracted increasing attention over the past decades due to its metal-insulator phase transition at temperature around 68 °C. This phase change is accompanied by lattice change from monoclinic (dielectric) to tetragonal (metal), lattice shrinking in the metallic state, and stark difference in the infrared transmittance between both phases. However, fabrication of VO2 thin films can be challenging due to other possible stoichiometric configurations, such as VO, V2O3, or V2O5. Many fabrication techniques have been used in recent years, where optimized fabrication process produces VxOy in the desired stoichiometry of VO2. In this Thesis, a summary of three deposition techniques suitable for the deposition of VO2 thin films is made and the process of creating thin samples (lamellae) suitable for study in the transmission electron microscopy (TEM) via focused ion beam (FIB) is described. Utilizing TEM with in-situ heating for characterization of VO2 samples produces valuable information on the microstructure of VO2 both below and above the transition temperature. In addition, electron energy-loss spectroscopy gives precious insight into the changing of different stoichiometries of VO2 in correlation to the thickness of the examined sample, near the sample edge in particular.
|
|
|
Electron microscopy and spectroscopy in plasmonics
Horák, Michal ; Krenn, Joachim (oponent) ; Shegai, Timur (oponent) ; Šikola, Tomáš (vedoucí práce)
This thesis deals with electron and ion beam techniques for fabrication and characterization of plasmonic nanostructures. Analytical electron microscopy focusing on applications in the field of plasmonics is discussed. The emphasis is given to electron energy loss spectroscopy (EELS) and cathodoluminescence. Further, fabrication of plasmonic samples for transmission electron microscopy is introduced while the aim is put at focused ion beam lithography and at sample preparation using chemically synthesized particles in water solution. The main research results are divided into four parts. The first part covers a comparative study of plasmonic antennas fabricated by electron beam and focused ion beam lithography. While both techniques are suitable for the fabrication of plasmonic antennas, electron beam lithography shall be prioritized over focused ion beam lithography due to better quality of the resulting antennas and considerably stronger plasmonic response in EELS. Antennas fabricated by focused ion beam lithography have slightly dull edges, exhibit pronounced thickness fluctuation, and they are also strongly contaminated not only by organic contaminants, but also by residues of FIB milling including implanted milling ions and atoms of a titanium adhesion layer. In the second part, Babinet's principle of complementarity for plasmonic nanostructures is investigated on a set of gold disc-shaped antennas and complementary apertures in a gold layer with various diameters. The complementarity is confirmed for fundamental plasmon properties such as resonance energies, but differences rising from the limited validity of Babinet's principle are found, for example, for the spatial distribution of the near-field of plasmon polaritons. The third part summarizes a study of nanostructures with functional properties related to the local enhancement of electric and magnetic field. Bow-tie and diabolo plasmonic antennas, both in the form of particles and in the form of apertures, exhibit particularly strong local field enhancement. Our study identifies several modes of localized surface plasmons in these antennas and characterizes their properties including mode energy, near field electric and magnetic field distribution, and the qualitative distribution of charge nodes and current associated with electron gas oscillations. Next, we have studied mode energy tunability in near infrared and visible spectral regions and focused on Babinet's complementarity between direct and inverted antennas. The last part is focused on silver amalgam, which is a novel and very prospective plasmonic material. By changing the size of silver amalgam nanostructures their plasmon resonance can be tuned from ultraviolet through the whole visible to infrared region. As silver amalgam is well investigated in the field of electrochemistry, silver amalgam nanoparticles opens a possibility to combine plasmonics and electrochemistry together.
|
|
|
Babinet principle for plasmonic antennas: complementarity and differences
Horák, M. ; Křápek, V. ; Hrtoň, M. ; Metelka, O. ; Šamořil, T. ; Stöger-Pollach, M. ; Paták, Aleš ; Šikola, T.
Plasmonics deals mainly with surface plasmon polaritons (SPP), which are collective oscillations of free electrons at metal-dielectric interfaces connected with the local electromagnetic field. When SPP are spatially restricted to a metallic nanoparticle, we talk about localized surface plasmons (LSP). LSP resonances can be characterized with an excellent spectral and spatial resolution by electron energy loss spectroscopy (EELS) and cathodoluminescence. Both techniques utilize an electron beam that interacts with the metallic nanoparticle and excites the LSP resonances. EELS measures the energy transferred from electrons to the LSP and cathodoluminescence deals with the light which the LSP emit during their decay. Babinet principle, originating in the wave theory of light and analysis of diffraction, relates the optical response of apertures in thin films and their complementary particle analogues. According to the Babinet principle, LSP in complementary particles and apertures have identical resonance energies and their near fields are closely linked: the electric field distribution of a specific in-plane polarization for an aperture corresponds to the magnetic field distribution of a perpendicular polarization for a particle.
|
host ::
RSS.