Size Dependence of Doping by a Vacancy Formation Reaction in Copper Sulfide Nanocrystals

Abstract

Doping of nanocrystals (NCs) is a key, yet underexplored, approach for tuning of the electronic properties of semiconductors. An important route for doping of NCs is by vacancy formation. The size and concentration dependence of doping was studied in copper(I) sulfide (Cu S) NCs through a redox reaction with iodine molecules (I ), which formed vacancies accompanied by a localized surface plasmon response. X-ray spectroscopy and diffraction reveal transformation from Cu S to Cu-depleted phases, along with CuI formation. Greater reaction efficiency was observed for larger NCs. This behavior is attributed to interplay of the vacancy formation energy, which decreases for smaller sized NCs, and the growth of CuI on the NC surface, which is favored on well-defined facets of larger NCs. This doping process allows tuning of the plasmonic properties of a semiconductor across a wide range of plasmonic frequencies by varying the size of NCs and the concentration of iodine. Controlled vacancy doping of NCs may be used to tune and tailor semiconductors for use in optoelectronic applications.

Moving the Plasmon of LaB6 from IR to Near-IR via Eu-Doping

“…The physical properties of plasmonic materials are typically easy to tune because of their high carrier concentration and small size, where seemingly minor adjustments such as altering the particle shape or size have a substantial influence on the absorbance spectrum [ 1 ]. Vacancies also play a large role in tuning the optical properties of such materials, having a significant influence on free carrier density and doping constraints [ 6 , 7 ]. It′s even possible to fully tune the plasmon independent of dopant concentration in core-shell indium-tin-oxide nanoparticles [ 8 ] and by reducing holes in the valence band in copper sulfide [ 9 ].…”

Crystal structure dependent cation exchange reactions in Cu2−xS nanoparticles

“…During the last decades, there has been growing attention on colloidal copper sulfide Cu 2− x S nanoparticles (NPs), mainly owing to their near/mid-infrared (NIR and MIR)-active localized surface plasmon resonance (LSPR) responses. 1–10 Based on the LSPR, their unique applications including photothermal therapy, photocatalysis, two-photon upconversion as well as SERS probe are extensively exploited. 11–20 In addition to LSPR, the high mobility of Cu + in Cu 2− x S NP lattice, which can be readily exchanged by guest cations ( i.e.…”

Strong Purcell enhancement at telecom wavelengths afforded by spinel Fe3O4 nanocrystals with size-tunable plasmonic properties

“…7 Metal oxide, nitride and chalcogenide semiconducting nanomaterials have now been demonstrated to support true LSPRs and to do so from the visible to the MWIR. 6,7,10,11 Despite these advances in nanomaterial plasmonics, the principal materials studied to date exhibit limited dopability and environmental stability. Namely, simple metal oxides, e.g., In 2 O 3 , ZnO, CdO, are not amenable to p-type doping, while Cu chalcogenides, which can be used to access p-type doping, are unstable.…”

“…P-type doping in Cu-based materials depends on Cu vacancies, where Cu is notoriously mobile, affording limited long-term stability. 11 An alternative class of semiconducting metal oxides may hold the key to both dopability and stability-spinel metal oxides (sp-MOs). sp-MO systems can provide multiple doping modes for controlling free carrier density.…”