First-principles research on mechanism of sub-band absorption of amorphous silicon induced by ultrafast laser irradiation

Abstract

Black silicon fabricated by ultrafast laser is a promising material for infrared detection. However, the structure–property relationship in laser-fabricated amorphous Si is still unclear. By first-principles calculations, different distorted local structures are revealed depending on cooling rate. By comparing the evolutions of structure and property, the bond angle distribution is identified as a good structural descriptor for sub-band absorptions. Glass formation is not simply a freezing of liquid but involves certain structural transitions that happened between 1350 and 850 K. A glass-forming temperature of 1100 K is further revealed which agrees with experiments. The main thermal-management effect is the duration time of glass-forming process. A shorter-pulse laser leads to more distorted structures and thus more defect states and infrared absorptions.

Keywords

• Infrared absorptions
• Black silicon
• Laser modification
• First-principles calculations
• Molecular dynamics