Correlation between microstructural and optical-diffraction properties in femtosecond-laser-induced gratings of amorphous Co2MnSi film

Abstract

We studied the correlation between the microstructures and the optical diffraction properties in femtosecond-laser-induced gratings of an amorphous CO2MnSi (a-Co2MnSi) film. The a-Co2MnSi thin film was deposited on a glass substrate by using magnetron sputtering, and the crystallization of the a-Co2MnSi film was performed using two-beam interference of near-infrared ferntosecond-laser pulses. For the femtosecond-laser-interference crystallization using two 120-mu J laser beams, the diffraction intensity slowly increased with the laser shot count until it reached a maximum intensity around 25900 laser shots; then, the diffraction intensity gradually decreased. nom the cross-sectional and the plan-view transmission-electron-microscopy images of the laser-crystallized Co2MnSi regions, the crystallization reached deeper into the sample film under an optimized fluence condition. Meanwhile, a lower fluence beam resulted in a partially crystallized film, and a higher fluence beam made a partially damaged film. The femtosecond-laser-induced gratings consisted of alternating semicrystalline-Co2MnSi and polyerystalline-Co2MnSi bands with a period of about 2-mu m.