Distinguishing Optical and Acoustic Phonon Temperatures and Their Energy Coupling Factor under Photon Excitation in nm 2D Materials
Distinguishing Optical and Acoustic Phonon Temperatures and Their Energy Coupling Factor under Photon Excitation in nm 2D Materials
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DOI：
10.1002/advs.202000097
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发表时间：
2020-05-26
期刊：
影响因子：
15.1
通讯作者：
Yue, Yanan
中科院分区：
文献类型：
--
作者：
Wang, Ridong;Zobeiri, Hamidreza;Yue, Yanan
在光子激发下，2D材料经历从电子到光学声子（OP）和声学声子（AP）的级联能量转移。尽管建模工作很少，但区分OP和AP温度仍然是一个历史悠久的开放问题，更不用说表征其能量耦合因子（G）了。在这里，纵向/横向光学（LO/TO）声子，弯曲光学（ZO）声子，和AP的温度是通过构建稳定的和纳秒（ns）的声子间分支能量传输状态，并同时探测它们使用纳秒能量传输状态分辨拉曼光谱区分。Delta TOP -AP被测量为占拉曼探测温升的30%以上。通过完全排除声子级联能量转移效应，实现了纳米MoS 2和MoSe 2悬浮态本征面内热导率的测量，改写了二维材料的拉曼热导率测量。G（OP AP）的MoS 2，MoSe 2，和石墨烯纸（GP）的特点。对于MoS 2和MoSe 2，G（OP AP）在10（15）和10（14）W m（-3）K-1的量级，并且G（ZO AP）远小于G（LO/TO AP）。在ns激光激发下，G（OP AP）显着增加，可能是由于显着增加的热载流子人口减少的声子散射时间。对于GP，G（LO/TO AP）为0.549 × 10（16）W m（-3）K-1，与第一性原理模型的值0.41 × 10（16）W m（-3）K-1很好地吻合。
Under photon excitation, 2D materials experience cascading energy transfer from electrons to optical phonons (OPs) and acoustic phonons (APs). Despite few modeling works, it remains a long-history open problem to distinguish the OP and AP temperatures, not to mention characterizing their energy coupling factor (G). Here, the temperatures of longitudinal/transverse optical (LO/TO) phonons, flexural optical (ZO) phonons, and APs are distinguished by constructing steady and nanosecond (ns) interphonon branch energy transport states and simultaneously probing them using nanosecond energy transport state-resolved Raman spectroscopy. Delta TOP -AP is measured to take more than 30% of the Raman-probed temperature rise. A breakthrough is made on measuring the intrinsic in-plane thermal conductivity of suspended nm MoS2 and MoSe2 by completely excluding the interphonon cascading energy transfer effect, rewriting the Raman-based thermal conductivity measurement of 2D materials. G(OP AP) for MoS2, MoSe2, and graphene paper (GP) are characterized. For MoS2 and MoSe2, G(OP AP) is in the order of 10(15) and 10(14) W m(-3) K-1 and G(ZO AP) is much smaller than G(LO/TO AP). Under ns laser excitation, G(OP AP) is significantly increased, probably due to the reduced phonon scattering time by the significantly increased hot carrier population. For GP, G(LO/TO AP) is 0.549 x 10(16) W m(-3) K-1, agreeing well with the value of 0.41 x 10(16) W m(-3) K-1 by first-principles modeling.