Femtosecond Laser-induced Crystallization of Amorphous Sb2Te3 film and Coherent Phonon Spectroscopy Characterization and Optical Injection of Electron Spins

TL;DR

This study demonstrates femtosecond laser-induced crystallization of amorphous Sb2Te3 films, monitored by coherent phonon spectroscopy, and explores electron spin dynamics using time-resolved optical techniques, revealing potential for spintronic applications.

Contribution

It introduces a femtosecond laser crystallization method for Sb2Te3 and employs coherent phonon spectroscopy and spin dynamics analysis to characterize the process and properties.

Findings

Crystallization degree increases with laser fluence.

Coherent phonon modes indicate successful crystallization.

Spin relaxation dynamics confirm spin-dependent optical transitions.

Abstract

A femtosecond laser-irradiated crystallizing technique is tried to convert amorphous Sb2Te3 film into crystalline film. Sensitive coherent phonon spectroscopy (CPS) is used to monitor the crystallization of amorphous Sb2Te3 film at the original irradiation site. The CPS reveals that the vibration strength of two phonon modes that correspond to the characteristic phonon modes of crystalline Sb2Te3, enhances with increasing laser irradiation fluence (LIF), showing the rise of the degree of crystallization with LIF and that femtosecond laser irradiation is a good post-treatment technique. Time-resolved circularly polarized pump-probe spectroscopy is used to investigate electron spin relaxation dynamics of the laser-induced crystallized Sb2Te3 film. Spin relaxation process indeed is observed, confirming the theoretical predictions on the validity of spin-dependent optical transition selection rule and the feasibility of transient spin-grating-based optical detection scheme of spin-plasmon collective modes in Sb2Te3-like topological insulators.