Plasmon Modes Induced by Anisotropic Gap Opening in Au@Cu₂O Nanorods

Abstract

Integration of semiconductors with noble metals to form heteronanostructures can give rise to many interesting plasmonic and electronic properties. A number of such heteronanostructures have been demonstrated comprising noble metals and n-type semiconductors, such as TiO2 , ZnO, SnO2 , Fe3 O4 , and CuO. In contrast, reports on heteronanostructures made of noble metals and p-type semiconductors are scarce. Cu2 O is an unintentional p-type semiconductor with unique properties. Here, the uniform coating of Cu2 O on two types of Au nanorods and systematic studies of the plasmonic properties of the resultant core-shell heteronanostructures are reported. One type of Au nanorods is prepared by seed-mediated growth, and the other is obtained by oxidation of the as-prepared Au nanorods. The (Au nanorod)@Cu2 O nanostructures produced from the as-prepared nanorods exhibit two transverse plasmon peaks, whereas those derived from the oxidized nanorods display only one transverse plasmon peak. Through electrodynamic simulations the additional transverse plasmon peak is found to originate from a discontinuous gap formed at the side of the as-prepared nanorods. The existence of the gap is verified and its formation mechanism is unraveled with additional experiments. The results will be useful for designing metal-semiconductor heteronanostructures with desired plasmonic properties and therefore also for exploring plasmon-enhanced applications in photocatalysis, solar-energy harvesting, and biotechnologies.

Brightening and Guiding Single‐Photon Emission by Plasmonic Waveguide–Slit Structures on a Metallic Substrate

“…In previous works, the silver nanowire is usually placed on the dielectric substrate. [36][37][38][39] In this case, it is observed that the effective refractive index (n eff ) of the SPP waveguide mode decreases with the increase of the radius of the silver nanowire (black line with rectangle symbols in Figure 2b), which is opposite to the case when the silver nanowire is placed on the silver substrate (black line with rectangle symbols in Figure 2a). As a result, the SPP waveguide mode supported by the silver nanowire (placed on the glass substrate) is cutoff (the green dashed line in Figure 2b) when the radius of the silver nanowire is greater than 44 nm (r > 44 nm).…”

“…From the fabrication point of view, the nanoslit can be etched by helium-focused ion beam (Carl Zeiss Orion Plus helium ion microscope) in the single-crystalline silver nanowire. [49,50] In the previous work reported by Xu's group, [39] a slit with a width of 18 nm on the single-crystalline silver nanowire could be fabricated by using gallium FIB (FEI DB235). Moreover, Xu's work [39] reported that the effect of the ion beam had a minor influence on the silver nanowire waveguide properties.…”

“…[49,50] In the previous work reported by Xu's group, [39] a slit with a width of 18 nm on the single-crystalline silver nanowire could be fabricated by using gallium FIB (FEI DB235). Moreover, Xu's work [39] reported that the effect of the ion beam had a minor influence on the silver nanowire waveguide properties. By using the helium FIB (Carl Zeiss Orion Plus helium-ion microscope) [49,50] instead of the gallium FIB, much narrower (sub-5 nm) nanoslits can be etched on the single-crystalline silver nanowire.…”

Plasmonic superradiance of two emitters near a metal nanorod

“…It has nano-scaled size in one or all three dimentions and can interact resonantly with emitters through the strong near field. Plasmonic cavities and waveguides have been proposed as buliding blocks for highly integrated photonic circuits [13]. However, due to absorption in metal, plasmonic cavities have high losses and low quality factors.…”

“…The enhancement is much larger than for SR in free space. Here we consider plasmonic SR, i.e., emitters generate plasmons, as in [13], not photons. Our approach can be easily generalized to many emitters and used for calculating the statistical properties of SR as in [6].…”