Hydrogen‐Doping‐Induced Metal‐Like Ultrahigh Free‐Carrier Concentration in Metal‐Oxide Material for Giant and Tunable Plasmon Resonance

Abstract

The practical utilization of plasmon‐based technology relies on the ability to find high‐performance plasmonic materials other than noble metals. A key scientific challenge is to significantly increase the intrinsically low concentration of free carriers in metal‐oxide materials. Here, a novel electron–proton co‐doping strategy is developed to achieve uniform hydrogen doping in metal‐oxide MoO3 at mild conditions, which creates a metal‐like ultrahigh free‐carrier concentration approaching that of noble metals (1021 cm−3 in H1.68MoO3 versus 1022 cm−3 in Au/Ag). This bestows giant and tunable plasmonic resonances in the visible region to this originally semiconductive material. Using ultrafast spectroscopy characterizations and first‐principle simulations, the formation of a quasi‐metallic energy band structure that leads to long‐lived and strong plasmonic field is revealed. As verified by the surface‐enhanced Raman spectra (SERS) of rhodamine 6G molecules on HxMoO3, the SERS enhancement factor reaches as high as 1.1 × 107 with a detection limit at concentration as low as 1 × 10−9 mol L−1, representing the best among the hitherto reported non‐metal systems. The findings not only provide a set of metal‐like semiconductor materials with merits of low cost, tunable electronic structure, and plasmonic resonance, but also a general strategy to induce tunable ultrahigh free‐carrier concentration in non‐metal systems.

Efficient and Tunable Reflection of Phonon Polaritons at Built‐In Intercalation Interfaces

“…The minor errors are possibly caused by the ambiguous infrared permittivity of H x MoO 3 by referring to the literature. [ 41,42 ]…”

3D Visible‐Light‐Driven Plasmonic Oxide Frameworks Deviated from Liquid Metal Nanodroplets

“…It is also possible that a portion of hot electrons is contributed to the direct catalysis due to the relatively long hot charge carrier lifetimes in degenerate semiconductors. [ 49 ]…”

A photo-responsive p-Si/TiO2/Ag heterostructure with charge transfer for recyclable surface-enhanced Raman scattering substrates

“…It has been discovered to possess strong enhancement of selected Raman-active modes of adsorbed molecules, correlated to the red shift of absorption. [20][21][22][23][24] Different electronic mechanisms involving TiO 2 -to-molecule CT show results with significantly larger enhancement factors. Notably, the high photocatalytic effect of TiO 2 can realize the substrate UV self-cleaning and recyclable use.…”