Comparative study on the localized surface plasmon resonance of boron- and phosphorus-doped silicon nanocrystals.

Localized surface plasmon resonance (LSPR) of doped Si nanocrystals (NCs) is critical to the development of Si-based plasmonics. We now experimentally show that LSPR can be obtained from both B- and P-doped Si NCs in the mid-infrared region. Both experiments and calculations demonstrate that the Drude model can be used to describe the LSPR of Si NCs if the dielectric screening and carrier effective mass of Si NCs are considered. When the doping levels of B and P are similar, the LSPR energy of B-doped Si NCs is higher than that of P-doped Si NCs because B is more efficiently activated to produce free carriers than P in Si NCs. We find that the plasmonic coupling between Si NCs is effectively blocked by oxide at the NC surface. The LSPR quality factors of B- and P-doped Si NCs approach those of traditional noble metal NCs. We demonstrate that LSPR is an effective means to gain physical insights on the electronic properties of doped Si NCs. The current work on the model semiconductor NCs, i.e., Si NCs has important implication for the physical understanding and practical use of semiconductor NC plasmonics.