快速雷射脈衝加熱之金屬薄膜熱傳特性研究

Abstract

本文探討電子熱傳導係數與電子溫度之間的關係，並針對快速雷射加熱金屬薄膜的過程，建立能夠同時量測金屬熱傳導係數與電子-聲子連結因子的逆運算量測分析。逆運算結果顯示，在快速雷射加熱金屬薄膜的過程，電子熱傳導率與電子溫度的關係式所造成的影響並不重要。對敏感係數的理論分析顯示，用於逆運算的電子溫度最佳量測點應選取在雷測脈衝加熱表面溫度到達最高值後的電子溫度；在雷射脈衝加熱背面則應選取整個未平衡時間的電子溫度變化。此外，由於雷射加熱時間極為短暫而造成直接量測電子溫度變化的困難，以往研究都以量測薄膜的光學反射率變化來取代之。亦即光學反射率變化與電子溫度變化之間呈線性關係。本文逆運算結果顯示出此線性關係之適用性值得探討。

This thesis investigates the effect of the electron thermal conductivity on electron temperature in the microtime scale. Besides, an inverse analysis is performed for simultaneous estimation of both thermal conductivity and the electron-phonon coupling factor of thin metal films during nonequilibrium laser heating of metals. Consequently, the influence of the relation between the electron thermal conductivity to electron temperature on the two-step model is not so significant during short-pulse laser heating. Theoretical analyses on the sensitivity coefficients illustrate that optimal choices of measurements would include temperature variations at the front surface over the time interval after the electron temperature reaches its maximum, combined with measurements of temperature variations at the rear surface for the whole thermalization time. Furthermore, we discuss whether we could regard the linear variation of the reflectivity as changed with the electron temperature when the laser pulse duration is too short to measure the variation of electron temperature directly. Results show that the linear relationship of the reflectivity and electron temperature leaves us a matter for future consideration.