Mechanistic Aspect of Surface Modification on Glass Substrates Assisted by Single Shot Pulsed Laser-Induced Fragmentation of Gold Nanoparticles

Abstract

This paper describes the mechanistic investigation on the photomodification of a borosilicate glass substrate assembled with 47 +/- 8 nm gold nanoparticles and exposed to a single shot of 532 nm nanosecond pulsed-laser light. The laser fluences ranging from 180 to 430 mJ cm(-2) pulse(-1), the values of which are 2 orders of magnitude lower than the breakdown threshold of quartz of 15-20 J cm(-2) pulse(-1) were used. Upon photomodification, the craters of similar to 20 nm diameter and similar to 10 tun depth were formed on the glass surface simultaneously with the laser-induced splitting of Au nanopartides to generate smaller particles of 15 nm diameter. The number density of the craters increased depending on the laser fluence with a sharp rise, the onset of which occurred at similar to 160-170 mJ cm(-2) pulse(-1), and reached a value of twice the number density of original Au particles (150 +/- 10 particles mu m(-2)) with a weak tendency to level off at high fluences. The onset of the crater formation coincides with splitting of gold nanopartides due to the temperature rise above the boiling point of gold resulting from the absorption of the laser energy. Thus, the explosive evaporation of gold nanoparticles is postulated to play a crucial role for the modification observed here. This assumption gained a solid support from the estimation of laser fluence-dependent thermoacoustic pressures due to the sudden evaporation of gold. This finding may represent a new application of the laser ablation/fragmentation of nanoparticles to material processing.