There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

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Plasmonics: Fundamentals and Applications

Recent years have seen a rapid expansion of research into nanophotonics based on surface plasmon–polaritons. These electromagnetic waves propagate along metal–dielectric interfaces and can be guided by metallic nanostructures beyond the diffraction limit. This remarkable capability has unique prospects for the design of highly integrated photonic signal-processing systems, nanoresolution optical imaging techniques and sensors. This Review summarizes the basic principles and major achievements of plasmon guiding, and details the current state-of-the-art in subwavelength plasmonic waveguides, passive and active nanoplasmonic components for the generation, manipulation and detection of radiation, and configurations for the nanofocusing of light. Potential future developments and applications of nanophotonic devices and circuits are also discussed, such as in optical signals processing, nanoscale optical devices and near-field microscopy with nanoscale resolution.

Plasmonics beyond the diffraction limit

Magnetic skyrmions are particle-like nanometre-sized spin textures of topological origin found in several magnetic materials, and are characterized by a long lifetime. Skyrmions have been observed both by means of neutron scattering in momentum space and microscopy techniques in real space, and their properties include novel Hall effects, current-driven motion with ultralow current density and multiferroic behaviour. These properties can be understood from a unified viewpoint, namely the emergent electromagnetism associated with the non-coplanar spin structure of skyrmions. From this description, potential applications of skyrmions as information carriers in magnetic information storage and processing devices are envisaged.

Topological properties and dynamics of magnetic skyrmions

Plasmons in strongly coupled metallic nanostructures.

Two-dimensional gold-nanorod arrays (2D-GNA) exhibit distinct resonance peaks in the visible wavelength range that are clearly associated with long and short axis plasmon oscillations. In this paper, we demonstrate a flexible and reproducible way for controlling the plasmon resonance of such 2D-GNAs in-situ, even post-fabrication process, simply by embedding free-standing nanorod arrays into an elastomer thin film. Stretching the polymer film shows the plasmon long-axis resonance to red-shift proportionally to the applied force by as much as 20~nm by increasing the center-to-center distance between individual nanorods. Releasing the load elastically relaxes the stretched polymer film, hence allowing the recording of cyclic load curves while varying the spectral response in-situ. Notably, film stretching along the substrate plane (x-axis) results in a uniaxial distortion of the nanorod lattice. We show how to account for this anisotropic strain in both the experiment and our complementary finite element modelling simulations, which then both match very well. This novel work illustrates both the feasibility and reliability when integrating 2D-GNAs for potential flexible, plasmonic applications.

Mechanical tuning of plasmon resonances in elastic, two-dimensional gold-nanorod arrays

The surface properties of films made of p-methoxyphenacyl derivative terpolymers, associated with photocleavage by UV irradiation, and their optical patterning are investigated. The deprotection reaction has been monitored by UV and FTIR spectroscopy, contact angle measurements, and X-ray photoelectron spectroscopy, revealing the photoremoval of the protecting p-methoxyphenacyl group in high yields under mild conditions. Parallel and serial patterning of the films has been performed by selective irradiation through optical masks and by laser irradiation via fiber tips of a scanning near-field optical microscope, respectively. By irradiation of photolabile protected functional groups, free carboxylic groups become exposed to the surface with which fluorescent dyes and proteins can be associated specifically.

Photolabile carboxylic acid protected terpolymers for Surface Patterning. Part 2: Photocleavage and Film Patterning

Improving Nano-Optical Simulations Through Curved Elements Implemented within the Discontinuous Galerkin Method Computational

Increasing demands for new computer architectures may require embedded non-volatile memories as for example in-memory computing. Ferroelectric field-effect transistors (FeFETs) add further advantages besides their outstanding properties due to the availability of both n-type and p-type transistors. The latter favor a different channel materials, like SiGe, due to the low hole mobility in silicon. In this article, we demonstrate the integration of ferroelectric hafnium oxide on SiGe as well as working p-type FeFETs, possessing a large memory window of about 1.1 V and low variability. Such architectures were co-integrated into a standard high-k metal gate (HKMG) CMOS platform. Furthermore, we report on the impact of annealing temperature on the interface and ferroelectric layer, which appears to be universal for SiGe and Si substrates. Here, a growth of the interface layer during annealing at higher temperatures was observed as well as a reduction of the wake-up effect for the ferroelectric layer.

Integration of Hafnium Oxide on Epitaxial SiGe for p-type Ferroelectric FET Application

In the field of molecular electronics thin films of molecules adsorbed on insulating surfaces are used as the functional building blocks of electronic devices. A control of the structural and electronic properties of the thin films is required for a reliable operating mode of such devices. Here, noncontact atomic force and Kelvin probe force microscopies have been used to investigate the growth and electronic properties of pentacene on KBr(001) and KCl(001) surfaces. Mainly molecular islands of upright standing pentacene are formed, whereas a new phase of tilted molecules appear near step edges on some KBr samples. Local contact potential differences (LCPD) have been studied with both Kelvin experiments and density-functional theory calculations. Large LCPD are found between the substrate and the differently oriented molecules, which may be explained by a partial charge transfer from the pentacene to the surface. The monitoring of the changes of the pentacene islands during dewetting shows that multilayers build up at the expense of monolayers. Moreover, in the Kelvin images, previously unknown line defects appear, which unveil the epitaxial growth of pentacene crystals.

Lukas M. Eng

Papers

Mechanical tuning of plasmon resonances in elastic, two-dimensional gold-nanorod arrays

Photolabile carboxylic acid protected terpolymers for Surface Patterning. Part 2: Photocleavage and Film Patterning

Improving Nano-Optical Simulations Through Curved Elements Implemented within the Discontinuous Galerkin Method Computational

Integration of Hafnium Oxide on Epitaxial SiGe for p-type Ferroelectric FET Application

Epitaxial Growth of Pentacene on Alkali Halide Surfaces Studied by Kelvin Probe Force Microscopy