Ultranarrow Mid-infrared Quantum Plasmon Resonance of Self-Doped Silver Selenide Nanocrystal

초록

The infrared quantum plasmon resonance (IR QPR) of nanocrystals(NCs) exhibits the combined properties of classical and quantum mechanics,potentially overcoming the limitations of conventional optical features.However, research on the development of localized surface plasmonresonance (LSPR) from colloidal quantum dots has stagnated, owingto the challenge of increasing the carrier density of semiconductorNCs. Herein, we present the mid-IR QPR of a self-doped Ag2Se NC with an exceptionally narrow bandwidth. Chemical modificationof the NC surface with chloride realizes this narrow QPR bandwidthby achieving a high free-carrier density in the NC. The mid-IR QPRfeature was thoroughly analyzed by using various experimental methodssuch as Fourier transform (FT) IR spectroscopy, X-ray photoelectronspectroscopy, and current-voltage measurements. In addition,the optical properties were theoretically analyzed using the plamon-in-a-boxmodel and a modified hydrodynamic model that revealed the effect ofcoupling with the intraband transition and the limited nature of electrondensity in semiconductor NCs. Integrating the quantum effect intothe plasmonic resonance reduces the peak bandwidth to 19.7 meV, whichis an extremely narrow bandwidth compared with that of the LSPR ofconventional metal oxide or metal chalcogenide NCs. Our results demonstratethat self-doped silver selenide quantum dots are excellent systemsfor studying mid-IR QPR.

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