Reflection and dielectric characteristics of TbDyFe thin film for high frequency MEMS sensors and actuators

The femtosecond pump-probe experimental device was designed to investigate reflection and dielectric properties of TbDyFe thin films. Tb_0.27Dy_0.73Fe₂ thin films were prepared by DC magnetron sputtering and the component, surface topography and crystalline property of TbDyFe thin films were measured by scanning electronic microscope (SEM) and atom force microscope (AFM). The extremum of reflectivity change corresponding to the electron thermalization was 100 plusmn 30 fs. Amplitude of extremum reaches its maximum at 160 mW pump fluence and it turns to zero at 0 mW and echo wave was found in reflectivity waveform. Combine with Fresnel reflect formula and K-K transformation, real and imaginary part of the complex dielectric constant was derived and it indicated that the absorption of thin film became greater with the increasing of reflection at surface after 0 ps delay time, but absorption of thin film recover to its initial state after 1 ps.