Single Femtosecond Laser-Pulse-Induced Superficial Amorphization and Re-Crystallization of Silicon

• Main Authors: Camilo Florian, Daniel Fischer, Katharina Freiberg, Matthias Duwe, Mario Sahre, Stefan Schneider, Andreas Hertwig, Jörg Krüger, Markus Rettenmayr, Uwe Beck, Andreas Undisz, Jörn Bonse
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Materials
• Subjects: femtosecond laser; silicon; amorphization; crystallization; spectroscopic imaging ellipsometry; transmission electron microscopy
• Online Access: https://www.mdpi.com/1996-1944/14/7/1651

Superficial amorphization and re-crystallization of silicon in <111> and <100> orientation after irradiation by femtosecond laser pulses (790 nm, 30 fs) are studied using optical imaging and transmission electron microscopy. Spectroscopic imaging ellipsometry (SIE) allows fast data acquisition at multiple wavelengths and provides experimental data for calculating nanometric amorphous layer thickness profiles with micrometric lateral resolution based on a thin-film layer model. For a radially Gaussian laser beam and at moderate peak fluences above the melting and below the ablation thresholds, laterally parabolic amorphous layer profiles with maximum thicknesses of several tens of nanometers were quantitatively attained. The accuracy of the calculations is verified experimentally by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (STEM-EDX). Along with topographic information obtained by atomic force microscopy (AFM), a comprehensive picture of the superficial re-solidification of silicon after local melting by femtosecond laser pulses is drawn.