Metallic etching by high power Nd:yttrium–aluminum–garnet pulsed laser irradiation

Abstract

A Nd:yttrium–aluminum–garnet pulsed laser, with 1064 nm wavelength, 9 ns pulse width, and 0.9 J maximum pulse energy, is employed to irradiate in vacuum different metal targets (Al, Ti, Ni, Cu, Ta, W, Au, and Pb). In order to measure the erosion thresholds, the etching rates, and the chemical yields, a mass quadrupole spectrometer is interfaced to the vacuum chamber. Etching process shows a threshold, which ranges between 0.1 and 1.6 J/cm2 for lead and tungsten, respectively. Etching rates range between 0.3 and 10 μg/pulse for copper and lead, respectively. The irradiation produces chemical yields ranging between 0.04 and 0.6 atoms/100 eV for copper and lead, respectively. A simple theoretical approach is presented to justify obtained results. The objective of collected data concerns the possibility to use ejected atoms, neutral and ionized, in an electron cyclotron resonance ion source, in order to provide high current, multiply charge ion beams.

Energy distributions of particles ejected from laser-generated pulsed plasmas

“…2. The ablation yields for the three metals show the existence of ablation thresholds, below which no ablation occurs, in agreement with literature [6]. Above the threshold the ablation yield increases linearly with the laser fluence.…”

Pulsed laser ablation of gold at 1064 nm and 532 nm

“…This experimental threshold is 20 J/cm 2 at 1 064 nm and 10 J/cm 2 at 532 nm. The experimental thresholds are in good agreement with the theoretical prevision values of 20 J/cm 2 for the infrared radiation and 12 J/cm 2 for the visible radiation, obtained by considering the minimum energy needed to evaporate, in vacuum, the volume of the irradiated gold target [8]. Because the diffusion length in 9 ns time in Au is higher with respect to the penetration depth, the irradiated mass practically is the same at the two wavelengths and the two thresholds are similar.…”

Optical-vortex laser ablation

“…Using this expression, the ablation-threshold fluence was evaluated to be about 1.5 J/cm 2 and 3.3 J/cm 2 for the OV with m = 2 and NVAB, respectively, on the assumption of same values in optical penetration depth ξ for both cases. This is a reasonable assumption since the optical penetration depth was determined by material parameters and incident wavelength [25].…”

“…Tantalum (Ta) plates were used as target samples. They exhibit low ablation threshold in comparison with other metals [23][24][25], which enables us to perform ablation experiment easily. Thickness of the Ta plates was ~1 mm and the plate surfaces were polished by sandpaper.…”