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How to Measure Hot Electron and Phonon Temperatures with Time Domain Thermoreflectance Spectroscopy?
ACS Photonics ( IF 6.5 ) Pub Date : 2022-10-31 , DOI: 10.1021/acsphotonics.2c01361
Stéphane Grauby 1 , Benjamin Vidal Montes 1 , Ahmad Zenji 1 , Jean-Michel Rampnoux 1 , Stefan Dilhaire 1
Affiliation  

Time domain thermoreflectance (TDTR) is a time-resolved technique aiming at evaluating electron and phonon temperatures. After a few picoseconds, when the thermal equilibrium is reached, the lattice temperature and the electron temperature are equal and an equilibrium thermoreflectance coefficient can be evaluated. In this work, we show that, whatever the probe wavelength, the thermoreflectance signal at equilibrium measured on a 50 nm gold transducer is proportional to the incident pump fluence. The thermoreflectance coefficient can then be identified for each probe wavelength, and lattice temperature variations can be deduced. At short time scales, the electrons can reach much higher temperatures than phonons and the thermoreflectance signal is mainly driven by the electronic contribution. In this nonequilibrium regime, the thermoreflectance signal amplitude is not linear with the incident pump fluence and does not follow the expected electron temperature variation. We have, however, identified a specific probe wavelength (490 nm) for which the electron thermoreflectance coefficient can be estimated. The TDTR technique then becomes finally a self-calibrated electron and phonon ultrafast thermometer.

中文翻译:

如何使用时域热反射光谱测量热电子和声子温度?

时域热反射 (TDTR) 是一种时间分辨技术,旨在评估电子和声子温度。几皮秒后,当达到热平衡时,晶格温度和电子温度相等,可以评估平衡热反射系数。在这项工作中,我们表明,无论探针波长如何,在 50 nm 金换能器上测得的平衡热反射信号与入射泵浦注量成正比。然后可以确定每个探测波长的热反射系数,并可以推断出晶格温度变化。在短时间尺度上,电子可以达到比声子高得多的温度,并且热反射信号主要由电子贡献驱动。在这种非平衡状态下,热反射信号幅度与入射泵注量不是线性的,并且不遵循预期的电子温度变化。然而,我们已经确定了一个特定的探测波长(490 nm),可以为其估计电子热反射系数。TDTR 技术最终成为一种自校准的电子和声子超快温度计。
更新日期:2022-10-31
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