Effect of chemically induced permittivity changes on the plasmonic properties of metal nanoparticles

Understanding chemical effects on the plasmonic properties of a metal nanomaterial due to the surface molecules on that metal is of great importance in the field of plasmonics and these effects have yet to be completely elucidated. Here, we report mechanisms of the chemically induced change in the electronic state at the metal-ligand interface of silver nanoparticles due to the ligand molecules, and the effect of this change on the plasmonic properties of those nanoparticles. It was found that changes in the electron density of states at the metal-ligand interface cause alterations in the induced and permanent dipole moments, and eventually to the permittivity at the interface, when the wave function near the Fermi level is localized at the interface. These alterations play a key role in determining the plasmonic properties of silver nanoparticles. The present findings provide a more precise understanding of the interconnection between the electronic states at the metal-organic interface and the plasmonic properties of the metal.

Boron Impurity Effect on the Structural, Elastic, and Electronic Properties of Titanium Carbide

Atomic, structural, and elastic properties of titanium carbide with the boron impurity have been studied in the framework of the density functional theory in the general gradient approximation, by using the software ABINIT. The calculations of the total energy of a TiC supercell with boron impurity atoms showed that the latter do not tend to form clusters in titanium carbide. The equilibrium distances between the adjacent planes of titanium atoms were found to increase in the presence of the boron impurity. The electronic spectra of TiC supercells with various numbers and positions of boron impurity atoms are analyzed. The presence of boron impurity atoms is found to result in the appearance of a subband of their electron states, which is located between the local electronic spectra of the 2s and 2p carbon states by about 0.24 Hartree below the Fermi level. The coordination positions of boron impurity atoms affect only the shape and half-width of their electronic subband. An insignificant increase in the electron density of states just below the Fermi level also takes place. The bulk modulus of a titanium carbide supercell with boron impurity atoms is calculated and analyzed.

Secondary electron emission measurement from Cr and Cu bombarded by an Ne10+ beam at 6 MeV/n

Backward secondary-electron-emission yield ($\delta$) from plates of 0.1 mm-thick Cu and 1 mm Cr and Al have been measured by irradiation of a fully stripped Ne$^{10+}$ beam at 6 MeV/$n$ stopped within each plate. A difference between $\delta$s from Cr and Cu larger than the ambiguity of this measurement ($\pm$3%) has been observed, with the discrepancy of the predicted small difference by kinetic emission based on stopping power and work function of each metal. The measured $\delta$ from Cr is larger than that from Cu, and also than previous measurements of other transition metals of the 3$d$ series, not only for the process of potential emission but also for kinetic. The conduction-electron density of states around the Fermi level calculated for the metals shows that the number of electrons just below the Fermi level and excited over it to an empty level by many kinds of reaction with the beam irradiation has to be considered. The number involved in this emission from Cr thus seems to be much larger than from Cu, which explains the relation of magnitudes for $\delta$. The measured $\delta$ from Al is larger than previous results, but is still consistent due to the existence of Al$_2$O$_3$ on the Al.