Detection of Localized Surface Plasmons on Metal Nanostructures

Tato bakalářská práce se zabývá teoretickým a experimentálním studiem lokalizovaných povrchových plazmonů vznikajících na kovových nanostrukturách. Analytické výpočty byly srovnány se simulacemi a s měřeními provedenými pomocí sestavené aparatury, pro infračervenou oblast byla využita fourierovská infračervená spektroskopie (FT-IR). Výsledky byly dále diskutovány s ohledem na platnost provedených aproximací a také na kvalitu vyrobených nanostruktur.This bachelor's thesis deals with theoretical and experimental study of localized surface plasmons excited on metal nanostructures. Analytical calculations were compared to simulations and measurements using assembled apparatus and Fourier-transform infrared spectroscopy (FT-IR) in infrared range. Obtained results were discussed considering both validity of performed approximations and quality of manufactured nanostructures.

Interaction of metallic nanoparticles and fast electrons

Rastrovací prozařovací elektronová mikroskopie je jednou ze základních technik vhodnou nejen pro zobrazování nanostruktur, ale může být také použita pro různé druhy spektroskopií a, jak bylo nedávno ukázáno, i pro nanomanipulaci. V této práci se zabýváme interakcí rychlých elektronů a kovových sférických nanočástic, konkrétně hliníkových a zlatých nanokuliček. Nejprve prezentujeme jak analytické, tak numerické výpočty spekter energiových ztrát elektronů a jejich analýzu pro různé parametry. Hlavní část práce je věnována teoretickým výpočtům sil působících na nanokuličku díky elektronu prolétávajícímu v její těsné blízkosti. Na základě našich nových výsledků odhalujících časový vývoj mechanické síly také navrhujeme možný mechanismus stojící za rozpohybováním nanočástic v elektronovém mikroskopu.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.

Dimensional Accuracy and Final Density Measurement of One-, Three-, and Eight-Unit Fixed Dental Frameworks Based on Co-Cr, Manufactured by Using Conventional, Additive and Subtractive Technologies

For the aim of this study, 90 fixed metal frameworks based on Co-Cr were made by using conventional lost vax technique, additive 3D printing done by Selective Laser melting (SLM) technique and subtractive manufacturing using CNC milling. Constructions were produced by the Ceramill Motion 2 milling machine (Amann Girrbach) and Mlab Cusing R 3D printer (GE Additive). Samples were made as one-, three- and eight-unit frameworks based on existing clinical cases. Initial stl. model was built up on a scanned plaster model of three clinical cases by ZirconZahn Modellier software. Evaluation of dimensional accuracy was made by comparison of initial stl. model with a scan of manufactured framework and analyzed by measurement software.  Density measurements were made by helium (He) based gas pycnometry.  Gained data was statistically analyzed by using T-test and F-test for technologies comparison and non-parametric form of ANOVA: Kruskal Wallis was applied in density evaluation of all samples

Single-Pixel Imaging in Space and Time with Optically-Modulated Free Electrons

Single-pixel imaging, originally developed in light optics, facilitates fast three-dimensional sample reconstruction, as well as probing with light wavelengths undetectable by conventional multi-pixel detectors. However, the spatial resolution of optics-based single-pixel microscopy is limited by diffraction to hundreds of nanometers. Here, we propose an implementation of single-pixel imaging relying on attainable modifications of currently available ultrafast electron microscopes in which optically-modulated electrons are used instead of photons to achieve sub-nanometer spatially- and temporally-resolved single-pixel imaging. We simulate electron beam profiles generated by interaction with the optical field produced by an externally programable spatial light modulator and demonstrate the feasibility of the method by showing that the sample image and its temporal evolution can be reconstructed using realistic imperfect illumination patterns. Electron single-pixel imaging holds strong potential for application in low-dose probing of beam-sensitive biological and molecular samples, including rapid screening during in-situ experiments.Comment: 25 pages, 4 figures, 3 supplementary figure

Spatio-spectral metrics in electron energy loss spectroscopy as a tool to resolve nearly degenerate plasmon modes in dimer plasmonic antennas

Electron energy loss spectroscopy (EELS) is often utilized to characterize localized surface plasmon modes supported by plasmonic antennas. However, the spectral resolution of this technique is only mediocre, and it can be rather difficult to resolve modes close in the energy, such as coupled modes of dimer antennas. Here, we address this issue for a case study of the dimer plasmonic antenna composed of two gold discs. We analyze four nearly degenerate coupled plasmon modes of the dimer: longitudinal and transverse bonding and antibonding dipole modes. With a traditional approach, which takes into account the spectral response of the antennas recorded at specific points, the modes cannot be experimentally identified with EELS. Therefore, we employ the spectral and spatial sensitivity of EELS simultaneously. We propose several metrics that can be utilized to resolve the modes. First, we utilize electrodynamic simulations to verify that the metrics indeed represent the spectral positions of the plasmon modes. Next, we apply the metrics to experimental data, demonstrating their ability to resolve three of the above-mentioned modes (with transverse bonding and antibonding modes still unresolved), identify them unequivocally, and determine their energies. In this respect, the spatio-spectral metrics increase the information extracted from electron energy loss spectroscopy applied to plasmonic antennas

Plasmonic Antennas with Electric, Magnetic, and Electromagnetic Hot Spots Based on Babinet's Principle

We theoretically study plasmonic antennas featuring areas of extremely concentrated electric or magnetic field, known as hot spots. We combine two types of electric-magnetic complementarity to increase the degree of freedom for the design of the antennas: bowtie and diabolo duality and Babinet's principle. We evaluate the figures of merit for different plasmon-enhanced optical spectroscopy methods and optical trapping: field enhancement, decay rate enhancement, quality factor of the plasmon resonances, and trapping potential depth. The role of Babinet's principle in interchanging electric and magnetic field hot spots and its consequences for practical antenna design are discussed. In particular, diabolo antennas exhibit slightly better performance than bowties in terms of larger field enhancement and larger Q factor. For specific resonance frequency, diabolo antennas are considerably smaller than bowties, which makes them favorable for the integration into more complex devices but also makes their fabrication more demanding in terms of spatial resolution. Finally, we propose a Babinet-type dimer antenna featuring electromagnetic hot spot with both the electric and magnetic field components treated on an equal footing