Valence EELS study of the composition of a liquid phase in a Janus Sn-Ge nanoparticle over a temperature range of 250-750 °C.

Sn-guided self-grown Ge stripes banded by GeSn Nanowires: Formation mechanism and electric-field-induced switching from p- to n-type conduction

In this work, we use electron energy-loss spectroscopy to map the complete plasmonic spectrum of aluminum nanodisks with diameters ranging from 3 to 120 nm fabricated by high-resolution electron-beam lithography. Our nanopatterning approach allows us to produce localized surface plasmon resonances across a wide spectral range spanning 2-8 eV. Electromagnetic simulations using the finite element method support the existence of dipolar, quadrupolar, and hexapolar surface plasmon modes as well as centrosymmetric breathing modes depending on the location of the electron-beam excitation. In addition, we have developed an approach using nanolithography that is capable of meV control over the energy and attosecond control over the lifetime of volume plasmons in these nanodisks. The precise measurement of volume plasmon lifetime may also provide an opportunity to probe and control the DC electrical conductivity of highly confined metallic nanostructures. Lastly, we show the strong influence of the nanodisk boundary in determining both the energy and lifetime of surface plasmons and volume plasmons locally across individual aluminum nanodisks, and we have compared these observations to similar effects produced by scaling the nanodisk diameter.

We investigated the mechanisms of secondary electron (SE) emission from Be(0001) by impact of 100 and 150 eV electrons. We made use of (e, 2e) spectroscopy to disentangle the different SE production mechanisms. We observed a large increase in the SE yield when the energy loss of the primary electron equals the characteristic energy of volume and surface plasmons. The line shape of the SE spectrum associated with plasmon excitation reveals that one relevant emission mechanism corresponds to direct single-particle excitation in which the plasmon energy and momentum are transferred to a valence band electron of the solid. The contributions to the SE yield associated with surface and volume plasmon excitation are comparable in the case of specular geometry, where the projectile momentum is mainly transferred perpendicular to the surface. On the contrary, the emission of SEs associated with surface plasmon excitation is significantly enhanced when the exchanged momentum lies close to the surface plane and electrons are emitted from Be surface state. This reflects the increased sensitivity to surface modes of the latter geometry. Finally, the coupling between the direct ionization channel and the plasmon-assisted one results in a resonant increase of the secondary emission.

We report here the measurements of the energy and dispersion of the surface plasmons on Ag single crystals in UHV using angle-resolved electron-energy-loss spectroscopy. The energy of small-momentum surface plasmons depends upon crystal face and, for Ag(110), upon crystal orientation. The differences in the energies of the surface plasmons, which cannot be explained by a jellium model, are discussed in terms of the contributions to the dielectric response from surface states and truncated bulk band states.

Effect of applying a direct current on wettability of liquid Sn-Pb/solid Cu

Phase Separation in Liquid Metal Nanoparticles

We investigated the local coefficient of thermal expansion (CTE) along the diameter of a 190 nm Sn nanoparticle supported on a thin Si₃N₄ substrate. The surface and volume plasmon energies of the liquid Sn nanoparticle were measured as a function of temperature using spatially resolved valence electron energy loss spectroscopy in a scanning transmission electron microscope. We found that the slope of the volume plasmon energy versus temperature gradually increased near the surface, revealing a thermal expansion gradient in liquid nanoparticles. This effect was confined to a 3 nm-thick surface layer, where the CTE was over 1.5 times larger than that of the nanoparticle core. Meanwhile, the CTE of the core was found to be smaller than the reference value for liquid Sn, which is attributed to mechanical constraints imposed by the thin Si₃N₄ substrate. We demonstrated that temperature-induced changes in surface plasmon energy provide insights into the CTE of the outmost surface layer of Sn nanoparticles.

Plasmon excitation in molecular tunnel junctions is interesting because the plasmonic properties of the device can be, in principle, controlled by varying the chemical structure of the molecules. The plasmon energy of the excited plasmons usually follows the quantum cutoff law, but frequently overbias plasmon energy has been observed, which can be explained by quantum shot noise, multielectron processes, or hot carrier models. So far, clear correlations between molecular structure and the plasmon energy have not been reported. Here, we introduce halogenated molecules (HS(CH2)12X, with X = H, F, Cl, Br, or I) with polarizable terminal atoms as the tunnel barriers and demonstrate molecular control over both the excited plasmon intensity and energy for a given applied voltage. As the polarizability of the terminal atom increases, the tunnel barrier height decreases, resulting in an increase in the tunneling current and the plasmon intensity without changing the tunneling barrier width. We also show that the plasmon energy is controlled by the electrostatic potential drop at the molecule-electrode interface, which depends on the polarizability of the terminal atom and the metal electrode material (Ag, Au, or Pt). Our results give new insights in the relation between molecular structure, electronic structure of the molecular junction, and the plasmonic properties which are important for the development of molecular scale plasmonic-electronic devices.

The excess enthalpies of liquid GaGeTe and GaSnTe alloys

Core level binding energy shifts in liquid binary alloys: AuGa

A series of Al-6.27 at. % Mg alloys were thermally evaporated in a vacuum at 1910 K. The length of time during which the alloy was molten and was evaporating was varied from very short times to a length of time sufficient for complete evaporation of the alloy. The thickness and average composition of the deposited films were determined with thin-film x-ray microanalysis in the analytical electron microscope. A solution/flux model was developed to simulate the evaporation process. The model treated the liquid Al-Mg alloy as a regular solution using experimentally determined Raoultian activity coefficients. The evaporative flux was calculated according to the expression of Langmuir. The solution and flux equations were numerically integrated with respect to time to accommodate changes in mass and liquid alloy composition as the molten alloy evaporated. The agreement between the model and the experimental data (evaporation rate, rate of composition change in the molten alloy, film thickening rate, and average film composition) was excellent. The experimental data and the results of the solution/flux model show that the Mg is evaporated from the melt very quickly. The time required for Mg depletion is approximately 3% of the time required for total evaporation of the alloy. The solution/flux model calculates an average activation energy for evaporation of 72 400±4000 cal/mol over the temperature range 1800–2400 K, which is in good agreement with the thermodynamic enthalpy change for vaporization of 72 300±2000 cal/mol at 2110 K.

Activity Coefficient of Oxygen in Liquid Sn and Liquid Alloys Containing Ge, Ni and Sn

Coherent controlling surface plasmon transport in metal nanowire coupled to quantum dot is investigated theoretically by real-space method. In the calculations, the dispersion relation of metal nanowire is supposed to be linear and the quantum dot is a cascaded three-level system. The calculations reveal that whether the surface plasmon is transmitted or reflected by turning off or on the classic field can be controlled. The surface plasmon transmission and reflection spectra can be controlled by adjusting the intensity and the circular frequency of classic optical field even the energy of surface plasmon and quantum dot is not matched. The dissipations affecting on the transport properties are also discussed.

The paper investigates non-radiative, near-field evanescent surface plasmon (SP) energy transport along the metallic nanowire by deriving the dispersion curves and damping relations through modified Bessel function based modal electromagnetic (EM) field expansion and transmission line analysis methods. By employing the Fabry-Perot resonator analysis and finite difference time domain (FDTD) simulation, the paper further demonstrates that the constructive multiple interference (L=npi/k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> ), skin depth (delta), and operational frequency (omega) play an essential role in determining the transmittance efficiency of SP energy transfer along the metallic nanowire.

We report on a nano-hole array structure with a single cavity beneath the perforated gold film. Structures were fabricated with a variety of cavity depths. The optical resonance of each structure as well as the surface plasmon (SP) energy matching between the top and bottom of the gold film were investigated. We also experimentally evaluated the sensitivity of the structures as surface plasmon resonance (SPR) sensors. We observed a 1.6-fold enhancement in bulk SPR sensitivity and a 3-fold improvement in figure of merit for a structure with a 350-nm cavity depth compared to a structure with a 5-nm cavity depth.