Picosecond transient thermoreflectance for thermal conductivity characterization
Picosecond transient thermoreflectance for thermal conductivity characterization
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DOI：
10.1080/15567265.2019.1580807
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发表时间：
2018-08
影响因子：
4.1
通讯作者：
Jihoon Jeong;Xianghai Meng;A. Rockwell;S. Bank;W. Hsieh;Jung‐Fu Lin;Yaguo Wang
中科院分区：
文献类型：
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作者：
Jihoon Jeong;Xianghai Meng;A. Rockwell;S. Bank;W. Hsieh;Jung‐Fu Lin;Yaguo Wang
利用低重复频率的皮秒脉冲激光(1064 Nm)作为加热源，以532 nm连续激光为探头，研制了一套用于热性质表征的皮秒瞬时热反射(PS-TTR)系统。低重复频率泵消除了热积累效应带来的复杂性。在不需要机械延迟台的情况下，该系统可以测量500ps到1ms的热衰减曲线。测试了三组样品：大块晶体(玻璃、硅、砷化镓和蓝宝石)、MoS2薄膜(157~900 nm厚度)、InGaAs随机合金和GaAs/InAs数字合金(短周期超晶格)。对热反射信号的分析表明，该系统能够同时测量纳米结构的热导率和界面电导。测量的大块晶体、MoS_2薄膜和InGaAs无规合金的热导率均与文献值一致。MoS_2薄膜的跨面热导率不表现出明显的厚度依赖性。由于在界面处的有效散射，GaAs/InAs数字合金的导热系数比InAs随机合金的小。我们还讨论了这种新开发的PS-TTR系统与流行的时域热反射系统相比的优缺点。
ABSTRACT We developed a picosecond transient thermoreflectance (ps-TTR) system for thermal property characterization, using a low-repetition-rate picosecond pulsed laser (1064 nm) as the heating source and a 532 nm CW laser as the probe. Low-repetition-rate pump eliminates the complication from thermal accumulation effect. Without the need of a mechanical delay stage, this ps-TTR system can measure the thermal decay curve from 500 ps up to 1 ms. Three groups of samples are tested: bulk crystals (glass, Si, GaAs, and sapphire); MoS2 thin films (157 ~ 900 nm thickness); InGaAs random alloy and GaAs/InAs digital alloy (short period superlattices). Analysis of the thermoreflectance signals shows that this ps-TTR system is able to measure both thermal conductivity and interface conductance in nanostructures. The measured thermal conductivity values in bulk crystals, MoS2 thin films, and InGaAs random alloy are all consistent with literature values. Cross-plane thermal conductivity in MoS2 thin films does not show obvious thickness dependence. Thermal conductivities of GaAs/InAs digital alloys are smaller than InGaAs random alloy, due to the efficient scattering at interfaces. We also discuss the advantages and disadvantages of this newly developed ps-TTR system comparing with the popular time-domain thermoreflectance system.