AI 中文总结
本研究以胶体量子点为对象，通过原位CL与PL测量明确其阴极荧光响应由电子束诱导带电主导，提出替换配体等策略实现双激子抑制，为稳定CL应用提供了可行路径。
AI 中文摘要
胶体量子点（QDs）是极具吸引力的纳米级发射器，但其阴极荧光（CL）响应在电子束激发下仍未被充分理解，且常表现出不稳定特性，限制了CL光谱学及基于电子束的器件加工。本研究采用光稳定性高、结构均匀的巨壳CdSe/CdS QDs，结合原位CL和光致发光（PL）测量，探究CL机制及提升其稳定性的策略。通过识别寿命与光谱测量中激发态的不同特征，证实CL响应由电子束诱导的带电现象主导。电荷积累即使在相对较低的电流下也会驱动多激子产生，导致明显的蓝移、更短的平均寿命及快速的阴极漂白。为进一步验证，研究采用间接激发实现低于典型电子束极限的亚pA级电流，结果显示中性激子发射可部分恢复，阴极漂白也得到缓解，但带电现象无法完全抑制。此外，通过用较短配体替换长绝缘配体，研究提升了电荷引流效率并强烈抑制了双激子形成。综上，研究表明可通过限制电荷积累控制双激子形成，为CL在光谱学、成像及电子束兼容光子器件中的稳定应用提供了可行途径。
英文摘要
Colloidal quantum dots (QDs) are attractive nanoscale emitters, yet their cathodoluminescence (CL) response remains poorly understood and often unstable under electron-beam excitation, limiting CL spectroscopy and electron-beam-based device processing. Here, we investigate the CL mechanism and strategies to improve its stability using highly photostable, structurally homogeneous giant-shell CdSe/CdS QDs combined with in situ CL and photoluminescence (PL) measurements. By identifying distinct signatures of excited states in both lifetime and spectral measurements, we demonstrate that the CL response is governed by electron-beam-induced charging. Charge accumulation drives multiexciton generation even at relatively low currents, leading to a pronounced blueshift, shorter average lifetimes, and rapid cathodobleaching. To test this further, we employ indirect excitation to reach sub-pA currents beyond the limits of typical electron beams, showing that neutral-exciton emission can be partially recovered and cathodobleaching mitigated, although charging cannot be fully suppressed. Furthermore, by replacing long insulating ligands with shorter ones, we improve charge drainage and strongly suppress biexciton formation. Together, these results show that biexciton formation can be controlled by limiting charge accumulation, providing a practical route toward stable CL for spectroscopy, imaging, and electron-beam-compatible photonic devices.
