Gigahertz longitudinal acoustic phonons originating from ultrafast ligand field transitions in hematite thin films  

作　　者：徐悦 金钻明 张郑兵 张泽宇 林贤 马国宏 程振祥 

机构地区：[1]Laboratory of Ultrafast Photonics, Department of Physics, Shanghai University [2]Max Planck Institute for Polymer Research, Ackermannweg 10,55128 Mainz, Germany [3]Institute for Superconductor and Electronic Materials, University of Wollongong, Squires Way

出　　处：《Chinese Physics B》2014年第4期288-291,共4页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant No.11174195)

摘　　要：The creation and propagation of longitudinal acoustic phonons （LAPs） in high quality hematite thin films （α-Fe203） epitaxially grown on different substrates （BaTiO3, SrTiO3, and LaAlO3） are investigated using the femtosecond pump- probe technique. Transient reflection measurements （AR/R） indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of -500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400- nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.The creation and propagation of longitudinal acoustic phonons （LAPs） in high quality hematite thin films （α-Fe203） epitaxially grown on different substrates （BaTiO3, SrTiO3, and LaAlO3） are investigated using the femtosecond pump- probe technique. Transient reflection measurements （AR/R） indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of -500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400- nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.

关 键 词：Α-FE2O3 pump-probe technique acoustic phonons ligand field 

分 类 号：O484[理学—固体物理]