Degenerately doped semiconductor nanocrystals (NCs) exhibit a localized surface plasmon resonance (LSPR) in the infrared range of the electromagnetic spectrum. Unlike metals, semiconductor NCs offer tunable LSPR characteristics enabled by doping, or via electrochemical or photochemical charging. Tuning plasmonic properties through carrier density modulation suggests potential applications in smart optoelectronics, catalysis and sensing. Here, we elucidate fundamental aspects of LSPR modulation through dynamic carrier density tuning in Sn-doped In₂O₃ (Sn:In₂O₃) NCs. Monodisperse Sn:In₂O₃ NCs with various doping levels and sizes were synthesized and assembled in uniform films. NC films were then charged in an in situ electrochemical cell and the LSPR modulation spectra were monitored. Based on spectral shifts and intensity modulation of the LSPR, combined with optical modelling, it was found that often-neglected semiconductor properties, specifically band structure modification due to doping and surface states, strongly affect LSPR modulation. Fermi level pinning by surface defect states creates a surface depletion layer that alters the LSPR properties; it determines the extent of LSPR frequency modulation, diminishes the expected near-field enhancement, and strongly reduces sensitivity of the LSPR to the surroundings.

简并掺杂的半导体纳米晶体（NCs）在电磁光谱的红外范围内表现出局部表面等离子体共振（LSPR）。与金属不同，半导体NC具有通过掺杂或通过电化学或光化学充电实现的可调LSPR特性。通过载流子密度调制来调整等离激元性质表明在智能光电，催化和传感方面的潜在应用。在这里，我们阐明了通过动态掺杂Sn掺杂的In ₂ O ₃（Sn：In ₂ O ₃）NC中的载流子密度来调节LSPR调制的基本方面。单分散Sn：In ₂ O ₃合成了具有不同掺杂水平和尺寸的NC，并组装成均匀的薄膜。然后将NC薄膜装入原位电化学池中，并监测LSPR调制光谱。基于LSPR的光谱偏移和强度调制，再结合光学建模，发现经常被忽略的半导体特性，特别是由于掺杂和表面状态引起的能带结构修改，对LSPR调制有很大影响。通过表面缺陷状态进行的费米能级钉扎会创建一个表面耗尽层，从而改变LSPR特性。它决定了LSPR调频的程度，减少了预期的近场增强，并极大地降低了LSPR对周围环境的敏感性。