Plasmonic Properties of Silicon Nanocrystals Doped with Boron and Phosphorus

Abstract

Degenerately doped silicon nanocrystals are appealing plasmonic materials due to silicon's low cost and low toxicity. While surface plasmonic resonances of boron-doped and phosphorus-doped silicon nanocrystals were recently observed, there currently is poor understanding of the effect of surface conditions on their plasmonic behavior. Here, we demonstrate that phosphorus-doped silicon nanocrystals exhibit a plasmon resonance immediately after their synthesis but may lose their plasmonic response with oxidation. In contrast, boron-doped nanocrystals initially do not exhibit plasmonic response but become plasmonically active through postsynthesis oxidation or annealing. We interpret these results in terms of substitutional doping being the dominant doping mechanism for phosphorus-doped silicon nanocrystals, with oxidation-induced defects trapping free electrons. The behavior of boron-doped silicon nanocrystals is more consistent with a strong contribution of surface doping. Importantly, boron-doped silicon nanocrystals exhibit air-stable plasmonic behavior over periods of more than a year.

Density functional theory study on the B doping and B/P codoping of Si nanocrystals embedded in SiO2

“…For example, low-energy light emission related to the transitions of electrons from the band edge to the defect state has been observed in boron (B)-and phosphorus (P)-doped Si NCs [20][21][22][23], leading to enhanced tunability of the light emission from Si NCs. In addition, heavy B and P doping have enabled localized surface plasmon resonance (LSPR) for Si NCs [24][25][26][27][28]. A series of novel devices that take advantage of the dopinginduced properties of Si NCs are now highly expected.…”

Size‐Dependent Structures and Optical Absorption of Boron‐Hyperdoped Silicon Nanocrystals

“…[ 19,20 ] For Si NCs, hyperdoping is also emerging as an effective means to obtain novel properties. [21][22][23][24][25][26] For instance, localized surface plasmon resonance (LSPR) may occur to hyperdoped Si NCs. [21][22][23] And the energy of the LSPR can be conveniently tuned by the doping level.…”

Optical Biosensing and Bioimaging With Porous Silicon and Silicon Quantum Dots (Invited Review)

“…This is very encouraging because the tuning of sizes can be achieved fairly easily in practice, which is usually done through colloidal chemistry or other fabrication techniques [92]. Another feature was the strong impact of doping on the optoelectronic properties of silicon nanocrystals, as evidenced from reported cases of both traditional dopants (B and P) and metals (Mn, Ni, Co, Cu) dopants [93,94].…”

“…Through controlling interactions of the charged clusters within the plasma, silicon nanocrystals with a broad range can be fabricated. This approach has been shown to be particularly attractive in performing doping experiments with silicon nanocrystals [94,130]. For instance, using nonthermal plasma synthesis, Kortshagen and coworkers have recently fabricated heavily doped boron and phosphorous doped silicon nanocrystals showing surface plasmons in the region of mid infrared [94,130].…”

“…This approach has been shown to be particularly attractive in performing doping experiments with silicon nanocrystals [94,130]. For instance, using nonthermal plasma synthesis, Kortshagen and coworkers have recently fabricated heavily doped boron and phosphorous doped silicon nanocrystals showing surface plasmons in the region of mid infrared [94,130]. This is particularly useful when the target applications are electronic and photonic devices, although it would be interesting to see whether the localized plasmon wavelength can be decreased to the near infrared region where bio-applications usually relies on.…”