Laser ablation of a platinum target in water. I. Ablation mechanisms

Abstract

This is the first in a series of three papers aimed at better understanding the processes that lead to nanomaterial formation during laser ablation of solid targets in liquids. Here we study the variation of the target surface morphology versus laser fluence and wavelength in order to suggest an ablation mechanism. A key finding is that an explosive ablation mechanism is prominent for a wide range of laser fluences for all wavelengths tested. Interestingly, however, ultraviolet (355nm) and infrared (1064nm) wavelengths show characteristically different explosive behaviors. In the infrared case, numerous large craters with diameters around 20μm form at localized points within the laser irradiated area. In contrast, ultraviolet ablation results in a striking transition to nanoscale surface roughness across the entire irradiated area. This texture is attributed to spinodal decomposition at the molten target surface. We propose that the wavelength and fluence dependence of the ablation craters can be explained by the amount of energy absorbed in the target. The consequences of the ablation mechanism for nanomaterial synthesis are discussed.

Cavitation bubble dynamics during pulsed laser ablation of a metallic glass in water

“…Therefore, the maximum laser intensity I max is estimated to be about 4 GW/cm 2 . This value is comparable to the explosive boiling thresholds for some crystalline and glassy metals [14,20,21]. On the edge of the irradiated area, surface ripples can be clearly observed (see Fig.…”

Platinum Nanoparticles as Photoactive Substrates for Mass Spectrometry and Spectroscopy Sensors

“…Irradiation at longer wavelengths will in turn favor explosive ejection of molten droplets. [35][36][37] These features aid in explaining the general observation that the ablated nanoparticles have gradually smaller overall size as the laser wavelength becomes shorter.…”

“…13, [35][36][37][38] The small NP size component is attributed to vaporization of atoms and small clusters from the irradiated target surface layer, 36 seeding further growth in the ablation plume. 38 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Bremsstrahlung 48 is, on one hand, considerably more favorable for IR than for UV wavelengths.…”

“…The pioneering work on PLAL for materials processing on the stabilizing agent. [35][36][37][38][39][40] Nichols et al 36 prepared platinum colloidal solutions at 1064, 532 and 355 nm using a nanosecond pulsed Q-switched Nd:YAG laser with high fluences (greater than 11 J cm -2 ), well above the ablation threshold. It was found that the nanoparticle size distribution has a qualitatively similar bimodal shape at the three wavelengths, although a greater yield of large NPs was observed with increasing laser fluence and wavelength.…”

Synthesis of Silver Nanoparticles with Laser Assistance

“…However, nucleation and growth do not represent the only mechanism of nanoparticle formation. Some experimental data show that another formation process, consisting in the ejection of metal drops or solid fragments from the target, so called "explosive boiling", are also take place at particular experimental conditions [45][46][47][48]. This second mechanism can be responsible for the formation of large (with sizes larger than about 100 nm) particles, that in turn, leads to the bimodal particle size distribution.…”