Coherent multiphoton photoelectron emission from single au nanorods: the critical role of plasmonic electric near-field enhancement.
Coherent multiphoton photoelectron emission from single au nanorods: the critical role of plasmonic electric near-field enhancement.
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DOI：
10.1021/nn305194n
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发表时间：
2013-01
期刊：
影响因子：
17.1
通讯作者：
A. Grubisic;V. Schweikhard;T. Baker;D. Nesbitt
中科院分区：
文献类型：
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作者：
A. Grubisic;V. Schweikhard;T. Baker;D. Nesbitt
利用扫描光电离显微镜研究了沉积在氧化铟锡（ITO）上的单个Au纳米棒在飞秒激光脉冲激发下，在棒纵向等离子体共振附近的电子发射.观察到所测量的电子信号强烈地依赖于激发激光的偏振和波长。相关的二次电子显微镜（SEM）和暗场显微镜（DFM）研究相同的纳米棒明确证实，最大的电子发射结果（i）激光偏振与棒的长轴和（ii）激光波长共振与局部表面等离子体共振。实验结果是在良好的一致性与定量预测的相干多光子光电效应，这是确定为主要的电子发射机制的金属纳米粒子在所采用的激发条件下。根据这一机制，多光子光发射率增加了超过10个数量级的局部表面等离子体共振附近，由于在粒子近场的入射电磁场的增强。这些发现将多光子光电发射识别为局部电场的极其敏感的度量（即，“热点”），其可以潜在地用于直接定量局部电场增强因子。
Electron emission from individual Au nanorods deposited on indium-tin-oxide (ITO) following excitation with femtosecond laser pulses near the rod longitudinal plasmon resonance is studied via scanning photoionization microscopy. The measured electron signal is observed to strongly depend on the excitation laser polarization and wavelength. Correlated secondary electron microscopy (SEM) and dark-field microscopy (DFM) studies of the same nanorods unambiguously confirm that maximum electron emission results from (i) laser polarization aligned with the rod long axis and (ii) laser wavelength resonant with the localized surface plasmon resonance. The experimental results are in good agreement with quantitative predictions for a coherent multiphoton photoelectric effect, which is identified as the predominant electron emission mechanism for metal nanoparticles under employed excitation conditions. According to this mechanism, the multiphoton photoemission rate is increased by over 10 orders of magnitude in the vicinity of a localized surface plasmon resonance, due to enhancement of the incident electromagnetic field in the particle near-field. These findings identify multiphoton photoemission as an extremely sensitive metric of local electric fields (i.e., "hot spots") in plasmonic nanoparticles/structures that can potentially be exploited for direct quantitation of local electric field enhancement factors.