Localized Plasmon Field Effect of Gold Clusters Embedded in Nanoporous Silicon

Coupling between nanoplasmonics and semiconducting materials can enhance and complement the efficiency of almost all semiconductor technologies. It has been demonstrated that such composites enhance the light coupling to nanowires, increase photocurrent in detectors, enable sub‐gap detection, allow DNA detection, and produce large non‐linearity. Nevertheless, the tailored fabrication using the conventional methods to produce such composites remains a formidable challenge. This work attempts to resolve that deficiency by deploying the immersion‐plating method to spontaneously grown gold clusters inside nano‐porous silicon (np‐Si). This method allows the fabrication of thin films of np‐Si with embedded gold nanoparticles (Au) and creates nanoplasmonic–semiconductor composites, np‐Si/Au, with fractional volume between 0.02 and 0.13 of the metallic component. Optical scattering measurements reveal a distinctive, 200 nm broad, localized surface plasmon (LSP) resonance, centered around 700 nm. Linear and non‐linear properties, and their time evolution are investigated by optically pumping the LSP resonance and probing the optical response with short wavelength infra‐red (2.5 휇 m) light. The ultrafast time‐resolved study demonstrates unambiguously that the non‐linear response is not only directly related to the LSP excitation, but strongly enhanced with respect to bare np‐Si, while its strength can be tuned by varying the metallic component.