Elliptical gold nanowires: controlled fabrication and plasmonic Fabry-Pérot resonances

Nanowires (NWs) are essential building blocks of photonic devices for guiding light waves. However, the controlled synthesis of non-circular NWs remains challenging. Herein, we develop a bottom-up approach for the fabrication of high-quality elliptical gold NWs with finely tuned geometry engineering by using an advanced ion-track template technology. Compared to ordinary NWs, the rotational symmetry breaking leads to highly polarization-dependent plasmonic responses. Modal analysis shows that the lowest dipolar HE₁ mode splits into two branches where the attenuation of the long-range branch decreases by 40%, while the short-range branch has a stronger enhanced near-field. Novel, to the best of our knowledge, plasmonic Fabry-Pérot resonances on finite NWs are measured. Our method can be extended to fabricate non-circular NWs with other materials, holding potential for novel applications from quantum to collective scales.

Surface Modification and Damage of MeV-Energy Heavy Ion Irradiation on Gold Nanowires

Gold nanowires with diameters ranging from 20 to 90 nm were fabricated by the electrochemical deposition technique in etched ion track polycarbonate templates and were then irradiated by Xe and Kr ions with the energy in MeV range. The surface modification of nanowires was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations. Different craters with and without protrusion on the gold nanowires were analyzed, and the two corresponding formation mechanisms, i.e., plastic flow and micro-explosion, were investigated. In addition, the sputtered gold nanoparticles caused by ion irradiation were studied and it was confirmed that the surface damage produced in gold nanowires was increased as the diameter of the nanowires decreased. It was also found that heavy ion irradiation can also create stacking fault tetrahedrons (SFTs) in gold nanowires and three different SFTs were confirmed in irradiated nanowires. A statistical analysis of the size distribution of SFTs in gold nanowires proved that the average size distribution of SFT was positively related to the nuclear stopping power of incident ions, i.e., the higher nuclear stopping power of incident ions could generate SFT with a larger average size in gold nanowires.

Controlled Structure of Electrochemically Deposited Pd Nanowires in Ion-Track Templates

Understanding and controlling structural properties of the materials are crucial in materials research. In this paper, we report that crystallinity and crystallographic orientation of Pd nanowires can be tailored by varying the fabrication conditions during electrochemical deposition in polycarbonate ion-track templates. By changing the deposition temperature during the fabrication process, the nanowires with both single- and poly-crystallinities were obtained. The wires with preferred crystallographic orientations along [111], [100], and [110] directions were achieved via adjusting the applied voltage and temperature during electrochemical deposition.