Research Topics

Plasmons and Plasmonics

Plasmonics has become a dynamic and quickly expanding field of technology since the beginning of the last decade. The practical appeal of plasmons arises from their potential use as carriers of information. The speed of information processing has risen rapidly at the same time as electronic processing components have shrunk. An impediment to further progress is the limited speed of data transfer using electronic means. Optical data transfer is significantly faster but the required components are large relative to the most highly developed electronic processing components. Information transfer using surface plasmons may offer a way to bridge the gap. The field of research investigating plasmon-based technologies and devices is called plasmonics; many devices have been proposed and are under development, such as waveguides, resonators, antennae and lenses.

By making use of the extraordinary energy resolution and isochromaticity of the SESAM equipped with the MANDOLINE filter we are studying plasmonic properties in a great variety of metallic nanostructures. We investigate surface plasmon resonances in confined metallic systems experimentally by EFTEM and STEM-EELS, and theoretically by FEM, DDA and 3D-FDTD. The aim is to map near-field profiles of electromagnetic modes where particle plasmons, long-range wedge plasmons, slot void plasmons or toroidal void plasmons are identified. Using EFTEM the spatial distribution of resonant features can be directly imaged even in rather complex structures.

Surface plasmons are collective oscillations of conduction electrons at the surfaces of metals. The coupling of plasmons and light and the propagation of surface plasmons have been intensively studied. An interesting application of surface plasmons is the localization of optical energies in metallic nanostructures using nanoantennas. We use energy-filtered transmission electron microscopy (EFTEM) and EELS to investigate localized surface plasmon (LSP) modes on gold tapers with different apex shapes and opening angles. The unique Zeiss SESAM electron microscope allows fine details at taper apices to be rendered with both high energy and high spatial resolution.

Investigation of plasmonic modes of gold tapers by EFTEM and EELS

Surface plasmons are collective oscillations of conduction electrons at the surfaces of metals. The coupling of plasmons and light and the propagation of surface plasmons have been intensively studied. An interesting application of surface plasmons is the localization of optical energies in metallic nanostructures using nanoantennas. We use energy-filtered transmission electron microscopy (EFTEM) and EELS to investigate localized surface plasmon (LSP) modes on gold tapers with different apex shapes and opening angles. The unique Zeiss SESAM electron microscope allows fine details at taper apices to be rendered with both high energy and high spatial resolution. [more]
Here, using EFTEM and EELS, we investigate the possible modes of void hexamer and heptamer plasmon resonators, focusing on their symmetries and topologies. The hexamer resonator has 6 holes of 70 nm diameter and rim-to-rim spacing of 30 nm, drilled into a 100 nm thick silver film. The heptamer resonator has 7 holes, one at the center and 6 in a ring. Each hole has a diameter of 60 nm and the rim-to-rim spacing is 50 nm. The structures have similar symmetry. However, they differ in the number of holes and the topology.

Investigation of void plasmon ring resonators

Here, using EFTEM and EELS, we investigate the possible modes of void hexamer and heptamer plasmon resonators, focusing on their symmetries and topologies. The hexamer resonator has 6 holes of 70 nm diameter and rim-to-rim spacing of 30 nm, drilled into a 100 nm thick silver film. The heptamer resonator has 7 holes, one at the center and 6 in a ring. Each hole has a diameter of 60 nm and the rim-to-rim spacing is 50 nm. The structures have similar symmetry. However, they differ in the number of holes and the topology. [more]




Previous Research Topics

Metamaterials are structures composed of man-made elements that exhibit a number of properties that are not available in natural materials, such as artificial magnetism at optical frequencies. One prototype of an individual element in magnetic metamaterials, the split-ring resonator (SRR), has attracted a lot of interest. A better understanding of the electromagnetic interactions between elements will facilitate the design of high performance metamaterials. The combination of electron energy-loss spectroscopy and scanning transmission electron microscopy allows us to visualize different plasmonic modes of SRRs in response to the evanescent electric field.

Numerical investigation of hybridization in coupled split-ring resonators

Metamaterials are structures composed of man-made elements that exhibit a number of properties that are not available in natural materials, such as artificial magnetism at optical frequencies. One prototype of an individual element in magnetic metamaterials, the split-ring resonator (SRR), has attracted a lot of interest. A better understanding of the electromagnetic interactions between elements will facilitate the design of high performance metamaterials. The combination of electron energy-loss spectroscopy and scanning transmission electron microscopy allows us to visualize different plasmonic modes of SRRs in response to the evanescent electric field. [more]
Monochromated valence electron energy-loss spectroscopy (VEELS) is used to study the plasmon energy (Ep) from strained GaN quantum wells (QWs) embedded in an AlN matrix. The primary specimen is a set of three wells with 4 nm, 3 nm, and 2 nm widths, separated by 30 nm thick AlN layers. The SESAM microscope is used to record EFTEM data and then a Gaussian function is fitted to the volume plasmon peak at each image pixel. After integration parallel to the QWs the plasmon energy profile is obtained. A distinct blue-shift of the plasmon peak position with decreasing QW width is observed.

Measurement of the volume plasmon energy from strained GaN quantum wells

Monochromated valence electron energy-loss spectroscopy (VEELS) is used to study the plasmon energy (Ep) from strained GaN quantum wells (QWs) embedded in an AlN matrix. The primary specimen is a set of three wells with 4 nm, 3 nm, and 2 nm widths, separated by 30 nm thick AlN layers. The SESAM microscope is used to record EFTEM data and then a Gaussian function is fitted to the volume plasmon peak at each image pixel. After integration parallel to the QWs the plasmon energy profile is obtained. A distinct blue-shift of the plasmon peak position with decreasing QW width is observed. [more]
 
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