Hostetler J L, Smith A N, Czajkowsky D M, Norris P M
Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22903, USA.
Appl Opt. 1999 Jun 1;38(16):3614-20. doi: 10.1364/ao.38.003614.
Femtosecond thermoreflectance data for thin films and bulk quantities of Au, Cr, and Al are compared with the parabolic two-step thermal diffusion model for the purpose of determining the electron-phonon coupling factor. The thin films were evaporated and sputtered onto different substrates to produce films that vary structurally. The measurement of the electron-phonon coupling factor is shown to be sensitive to grain size and film thickness. The thin-film thermoreflectance data are compared with that of the corresponding bulk material and to a theoretical model relating the coupling rate to the grain-boundary scattering and size effects on the mean free path of the relevant energy carrier.
为了确定电子 - 声子耦合因子，将金、铬和铝的薄膜及块状材料的飞秒热反射数据与抛物线两步热扩散模型进行了比较。这些薄膜通过蒸发和溅射沉积在不同的衬底上，以制备结构各异的薄膜。结果表明，电子 - 声子耦合因子的测量对晶粒尺寸和薄膜厚度敏感。将薄膜热反射数据与相应块状材料的数据以及一个将耦合速率与晶界散射和相关能量载流子平均自由程的尺寸效应联系起来的理论模型进行了比较。
