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本文通过抽运一探测技术,利用飞秒激光脉冲激发并探测了Fe/Si薄膜中的高频相干声学声子.通过经典的阻尼谐振函数,对声学声子的动力学行为进行了拟合.实验及拟合结果表明,该声学声子的共振频率约为0.25 THz,其退相时间约为12 ps,且都与激发光的波长和能量密度无关.声学声子的振幅随着激发光能量密度的增加而线性地增强.临界参数12_Τe-ph/T约为0.6,表明相干声学声子的驱动力主要来源于电子热应力的贡献.最后,结合薄膜的厚度和质量密度,可以得到室温下垂直于该.Fe/Si薄膜表面(out of plane)的弹性常数C_⊥约为283 GPa.
In this paper, we use the femtosecond laser pulses to excite and probe the high-frequency coherent acoustic phonons in the Fe / Si films by pumping a detection technique. The classical phonon damping dynamics are used to fit the dynamic behavior of acoustic phonons. Experimental and fitting results show that the acoustic phonon has a resonance frequency of about 0.25 THz and a retardation time of about 12 ps, which is independent of the wavelength and energy density of the excitation light. The amplitude of the acoustic phonon increases with the energy of the excitation light Density increases linearly.The critical parameter 12_Te-ph / T is about 0.6, indicating that the driving force of coherent acoustic phonon mainly comes from the contribution of electronic thermal stress.Finally, combined with the thickness and mass density of the film, it can be obtained at room temperature The elastic constant C_⊥ perpendicular to the out of plane of the Fe / Si film is about 283 GPa.