Applied Surface Science, Vol.419, 603-613, 2017
Droplet distribution during sub-picosecond laser deposition of gold nanoparticles
Even if it has been recently assessed that sub-picosecond ablation is not a "melting-free" process, a systematic investigation of the issue of droplets is still lacking. In this paper we discuss the effects of fluence (F= 0.3, 1,3 J/cm(2)), target-substrate distance (d(Ts) = 5, 6, 7, 8, 9 cm) and number of laser pulses per site (N-p/s = 2,12, 22, 36, 96) on the morphology in terms of droplets and plasmonic response of gold nanoparticles deposited by sub-picosecond pulsed laser ablation. Among metals, gold is an ideal candidate to study the occurrence of droplets due to its low electron-phonon coupling that favors the appearance of heat affected zones. Our findings demonstrate that N-p/s affects the production of large droplets more intensely than F and d(Ts). In fact, increasing N-p/s produced much larger droplets than the ones obtained by tuning the fluence and an increment in the droplet density of 10 times. On the other hand, while the maximum density of small droplets (average diameter <= 0.15 mu m) occurs at F =1 J/cm(2) (with respect to 0.3 J/cm(2) and 3 J/cm(2)), the total droplet density exhibits a minimum at such fluence. (C) 2017 Elsevier B.V. All rights reserved.
Keywords:Sub-picosecond laser ablation;Gold low electron-phonon coupling;Droplet distribution;Shots per site