尺寸效应下超快激光加热硅薄膜二维传热研究

Two-dimensional heat conduction study of ultra-fast laser heated thin silicon films under size effect

摘要:

超快激光技术目前较为广泛地应用于微纳米结构的加工,极小的尺寸产生了不同于宏观条件的传热特性,也逐渐成为人们研究的热点。文章采用改进双相滞导热(dual-phase-lagging,DPL) 模型对超快激光照射纳米硅薄膜的二维传热过程展开了理论研究。通过应用积分变化法求解了反映尺寸效应的改进DPL方程,分析了薄膜内部温度沿薄膜厚度方向和径向的变化规律。结果显示薄膜加热区域的温度迅速升高,随后能量会以波的形式逐渐向薄膜内部传递。在采用改进DPL模型得到的结果中热量的波状传递现象与DPL模型的结果相比更为平缓,将二维改进模型的结果同一维结果进行对比,发现在相同克努森数下,二维模型得到的温度要高于一维模型；且两者的差距会随着时间的推移愈发明显,表明二维传热过程中热量的径向传递对薄膜内部的温度分布具有重要影响。

Abstract:

Ultra-fast laser technology is now widely used in the processing of micro and nano structures.The extremely small size produces heat transfer characteristics different from macroscopic conditions and it has gradually become a research focus.An improved dual-phase-lagging (DPL) model is utilized to investigate the two-dimensional thermal conduction of nano-silicon films irradiated by ultra-fast laser.The modified DPL equation reflecting the size effect is solved by integral variation method.The variation of the internal temperature along the thickness direction and the radial direction of the thin film is analyzed.The result shows the temperature increases rapidly in the heated region of the film,and the energy is gradually transferred to the inside of the film in the form of waves.Although both the results based on the improved DPL model and the DPL model can obtain similar thermal wave temperature fields,the temperature distribution in the film obtained by the improved DPL model is relatively flat.Under the same Knudsen number,the temperature obtained by the two-dimensional improved DPL model is higher than that obtained by the one-dimensional model,and the temperature difference becomes larger and larger as time goes by,which implies that the radial heat conduction has an important effect on the temperature distribution inside the film in the two-dimensional heat transfer process.