[论文解读] Hot Carrier Dynamics in Photoexcited Gold Nanostructures: Role of Interband Excitations and Evidence for Ballistic Transport

Giulia Tagliabue, Adam S. Jermyn+6 more|CaltechAUTHORS (California Institute of Technology)|Aug 7, 2017

GaN-based semiconductor devices and materials参考文献 3被引用 70

一句话总结

该研究结合实验、第一性原理理论和玻尔兹曼传输计算，展示20 nm 金纳米结构的热电子以无散射方式注入到 Au-GaN 并强调带间激发效应。

ABSTRACT

Harnessing short-lived photoexcited electron-hole pairs in metal nanostructures has the potential to define a new phase of optoelectronics, enabling control of athermal mechanisms for light harvesting, photodetection and photocatalysis. To date, however, the spatiotemporal dynamics and transport of these photoexcited carriers have been only qualitatively characterized. Plasmon excitation has been widely viewed as an efficient mechanism for generating non-thermal hot carriers. Despite numerous experiments, conclusive evidence elucidating and quantifying the full dynamics of hot carrier generation, transport, and injection has not been reported. Here, we combine experimental measurements with coupled first-principles electronic structure theory and Boltzmann transport calculations to provide unprecedented insight into the internal quantum efficiency, and hence internal physics, of hot carriers in photoexcited gold (Au)-gallium nitride (GaN) nanostructures. Our results indicate that photoexcited electrons generated in 20 nm-thick Au nanostructures impinge ballistically on the Au-GaN interface. This discovery suggests that the energy of hot carriers could be harnessed from metal nanostructures without substantial losses via thermalization. Measurements and calculations also reveal the important role of metal band structure in hot carrier generation at energies above the interband threshold of the plasmonic nanoantenna. Taken together, our results advance the understanding of excited carrier dynamics in realistically-scaled metallic nanostructures and lay the foundations for the design of new optoelectronic devices that operate in the ballistic regime.

研究动机与目标

• 推动对金属纳米结构中光激发的电子-空穴对的时空动力学的理解。
• 量化内部量子效率以及支配热载流子产生、传输和注入的物理机制。
• 评估等离子激元激发和带间跃迁对现实纳米结构中热载流子行为的影响。

提出的方法

• 将实验测量与耦合的第一性原理电子结构理论结合起来。
• 使用玻尔兹曼传输计算来建模热载流子动力学。
• 分析Au-GaN界面的内部量子效率与弹道传输。
• 研究金属带结构在带间阈值之上的热载流子产生中的作用。

实验结果

研究问题

• RQ1 在20 nm的金纳米结构中产生的光激发电子是否以弹道方式撞击 Au-GaN 界面？
• RQ2 带间激发在金纳米结构中热载流子产生与传输中起何作用？
• RQ3 金属带结构如何影响高于带间阈值的热载流子产生？

主要发现

• 来自20 nm金纳米结构的热电子以弹道方式撞击Au-GaN界面。
• 带间激发在高于等离子体带间阈值的能量范围内的热载流子产生中起重要作用。
• 金属带结构在相关能量范围显著影响热载流子产生。
• 结果为内部量子效率提供了见解，并展示在不产生显著热化损失的情况下利用热载流子的潜力。
• 该工作支持在现实尺度金属纳米结构中以弹道极限工作设备的设计原则。