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首页> 外文期刊>International Journal of Heat and Mass Transfer >Theoretical and experimental study on the heat transport in metallic nanofilms heated by ultra-short pulsed laser
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Theoretical and experimental study on the heat transport in metallic nanofilms heated by ultra-short pulsed laser

机译：超短脉冲激光加热金属纳米膜传热的理论和实验研究

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摘要

In this paper the mechanism of heat transport in metallic nanofilms under ultra-short pulsed laser heat-ing is examined theoretically and experimentally. In order to easily understand the non-equilibrium heat transport in metallic nanofilms the study of heat transport behavior is first carried out in dielectrics. The analyses indicate that there may be two kinds of wave phenomena in dielectrics subjected to a periodic surface temperature. One is the thermal wave governed by the C-V model based hyperbolic equation and the other is the diffusive wave governed by the Fourier model based parabolic equation. According to the hyperbolic two step model for non-equilibrium heat transport, such two kinds of wave phenomena can also occur simultaneously in the metallic nanofilms under pulsed laser heating, where the diffusive wave is induced by the electron temperature oscillation at the surface due to the non-equilibrium between electrons and lattices. Unlike the propagation speed of the thermal wave, the propagation speed of the diffusive wave depends not only on the medium properties but also the period of the temperature oscil-lation at the boundary. Hence, the propagation speed of the diffusive wave in the electron gas may be of as high as 10~6 m s~(- 1) when the laser pulse duration is less than 1 ps. A transient thermoreflectance (TTR) system has been built to measure the transient electron temperature responses caused by the femtosecond laser heating and a pump-probe technique is used to ensure the femtosecond temporal resolution in the experiments. Different from the commonly used front heating-front detecting (FF) method for measuring the material properties, a rear heating-front detecting (RF) method is applied, so that measuring the propagation speed of heat becomes available. The non-equilibrium heat diffusion model is used to fit the measured normalized electron temperature profiles of 27.2 nm, 39.9 nm and 55.5 nm Au films. The best-fitted coupling factor C basically agrees with the theoretical value 2.3 x 10~(16) W m~3 K~(-1). The prop-agation speed of the diffusive wave in the electron gas can be obtained by comparing the measured delay time of peak electron temperatures of Au films with different thicknesses. The average propagation speed of the temperature oscillation or diffusive wave in Au films for the range of thickness from 27.2 nm to 55.5 nm is equal to 8.1 x 10~5 m s-1, which is close to the value predicted by the non-equilibrium heat dif-fusion model.
机译：本文从理论和实验上研究了超短脉冲激光加热下金属纳米膜中热传递的机理。为了容易理解金属纳米膜中的非平衡热传递，首先在电介质中进行热传递行为的研究。分析表明，受周期性表面温度影响的电介质中可能存在两种波现象。一种是由基于C-V模型的双曲方程控制的热波，另一种是由基于傅立叶模型的抛物方程控制的扩散波。根据非平衡传热的双曲两步模型，在脉冲激光加热下，金属纳米膜中也可能同时发生两种波现象，其中扩散波是由表面电子温度振荡引起的。电子和晶格之间的非平衡。与热波的传播速度不同，扩散波的传播速度不仅取决于介质的性质，还取决于边界处温度振荡的周期。因此，当激光脉冲持续时间小于1ps时，电子气体中扩散波的传播速度可能高达10〜6m s〜（-1）。已经建立了瞬态热反射（TTR）系统来测量由飞秒激光加热引起的瞬态电子温度响应，并使用泵浦探测技术来确保实验中的飞秒时间分辨率。与通常用于测量材料特性的前加热前检测（FF）方法不同，应用了后加热前检测（RF）方法，因此可以测量热量的传播速度。非平衡热扩散模型用于拟合27.2 nm，39.9 nm和55.5 nm Au薄膜的测量归一化电子温度曲线。最佳拟合耦合因子C基本与理论值2.3 x 10〜（16）W m〜3 K〜（-1）一致。通过比较不同厚度的金膜的峰值电子温度的测量延迟时间，可以获得电子气中扩散波的传播速度。在厚度为27.2 nm至55.5 nm的范围内，Au膜中温度振荡或扩散波的平均传播速度等于8.1 x 10〜5 m s-1，接近于非平衡所预测的值热扩散模型。

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  • 来源
    《International Journal of Heat and Mass Transfer》 |2011年第4期|p.967-974|共8页
  • 作者

    Hai-Dong Wang; Wei-Gang Ma; Xing Zhang; Wei Wang; Zeng-Yuan Guo;

  • 作者单位

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China;

    lnstitute of Microelectronics, Peking University, Beijing 100871, China;

    Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    thermal wave; diffusive wave; non-equilibrium heat transport; thermoreflectance measurement;

    机译：热波扩散波非平衡传热折光率测量;

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