Sokolowski-Tinten K, Shen X, Zheng Q, Chase T, Coffee R, Jerman M, Li R K, Ligges M, Makasyuk I, Mo M, Reid A H, Rethfeld B, Vecchione T, Weathersby S P, Dürr H A, Wang X J
Faculty of Physics and Centre for Nanointegration Duisburg-Essen, University of Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg, Germany.
SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, California 94025, USA.
Struct Dyn. 2017 Jul 21;4(5):054501. doi: 10.1063/1.4995258. eCollection 2017 Sep.
We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer. This behavior is attributed to a cross-interfacial coupling of excited electrons in the Au film to phonons in the adjacent insulator layer(s). Analysis of the data using the two-temperature-model taking explicitly into account the additional energy loss at the interface(s) allows to deduce the relative strength of the two relaxation channels.
我们应用时间分辨兆电子伏特电子衍射来研究薄膜金-绝缘体异质结构中的电子-晶格能量弛豫。通过对瞬态德拜-瓦勒因子的精确测量，直接确定了原子位移的均方值，这使得我们能够定量跟踪短脉冲激光激发后晶格温度的时间演化。在扩展的激光能量密度范围内获得的数据表明，当薄膜厚度减小或金膜被额外的绝缘体顶层覆盖时，弛豫速率会增加。这种行为归因于金膜中受激电子与相邻绝缘层中的声子之间的跨界面耦合。使用双温模型对数据进行分析，并明确考虑界面处的额外能量损失，可以推断出两个弛豫通道的相对强度。
