Xi-Ping Hao

Surface-plasmon-enhanced transmission through metallic film perforated with fractal-featured aperture array

A fractal-featured metallic thin film with Sierpinski Carpet pattern is fabricated on silicon wafer by microfabrication techniques. Transmission infrared spectroscopy indicates that there exists extraordinary high transmission at specific wavelengths, which can be ascribed to the effect of surface plasmon resonance, and are determined by hierarchy of apertures of different sizes in the fractal structure. This patterned film provides a unique system to achieve enhanced transmission simultaneously at different selected frequencies of electromagnetic wave.

Characterization of periodically nanostructured copper filaments self-organized by electrodeposition

We report in this paper the electric properties of nanostructured copper filament arrays self-organized by a novel electrochemical method. Due to the spontaneous oscillation of the concentration field of [Cu2+ ] in front of the growing interface, crystallites of copper and cuprous oxide appear alternately on the filaments of the electrodeposits. A conducting atomic force microscope (CAFM) and current imaging tunnelling spectroscopy (CITS) were used to characterize the electric properties of the nanostructured copper filaments. By applying a constant voltage across the conducting probe of the CAFM and the sample, an electric current mapping is achieved, in which alternating low and high current regions correspond exactly to the periodic nanostructures on the filaments. The profile of the electric current along the structured filament has been analysed, and no noticeable potential drop has been observed. A typical linear I–V curve for a metal and nonlinear I–V curve for a semiconductor were collected in the high and low current regions respectively. These results suggest that despite the periodic distribution of Cu2O crystallites on the deposited filament, there should exist a metallic core of copper crystallites inside the filament. This type of structured metal–semiconductor filament might have potential application.

Fabrication of stereo metallic resonant structures with polymer droplets as template

Using polymer droplets formed in dewetting of polymer film on silicon surface as template, the silicon columns capped with circular polymer plates are fabricated via plasma etching. By blanket deposition of a gold layer on the structure, an array of metallic microcavities featured by a metal circular plate separated by a silicon column with the bottom metallic film is achieved. The geometrical parameters of the stereo structures can be tuned. We show that the electric field at the edge of the cap is greatly enhanced, which can be used as the hot spot for trace amount of chemical detection.