Fs Laser Patterning of Amorphous As₂S₃ Thin Films

Area of Science:

• Materials Science
• Laser Physics
• Nanotechnology

Background:

• Arsenic trisulfide (As₂S₃) thin films are crucial in optical applications.
• Understanding laser-induced modifications is key for material processing.
• Pulsed laser deposition (PLD) is a common technique for thin film growth.

Purpose of the Study:

• To investigate femtosecond (fs) laser-induced morphological changes in As₂S₃ thin films and Au\As₂S₃ heterostructures.
• To determine the power threshold for photoexpansion and photoevaporation phenomena.
• To compare fs laser effects with continuous-wave (cw) laser irradiation.

Main Methods:

• Thin films of As₂S₃ and Au\As₂S₃ heterostructures were grown using pulsed laser deposition (PLD).
• A direct laser writing setup was used for systematic irradiation with fs laser pulses.
• Atomic Force Microscopy (AFM) was employed for morphological and topological characterization.

Main Results:

• A distinct transition threshold between photoexpansion and photoevaporation was observed between 1 and 1.5 mW, independent of irradiation time.
• The presence of a gold layer in Au\As₂S₃ heterostructures had a negligible effect on this threshold.
• Maximum photoexpansion was 5.2% in As₂S₃ films and 0.8% in Au\As₂S₃ heterostructures.

Conclusions:

• Femtosecond laser pulses efficiently induce photoexpansion in As₂S₃ thin films.
• The observed threshold is consistent across different irradiation times and minimally affected by gold incorporation.
• Fs laser irradiation is more effective for inducing photoexpansion compared to cw laser irradiation.