Existence of phase explosion during laser ablation and its effects on inductively coupled plasma-mass spectroscopy

A sudden increase in crater depth was observed during high irradiance (> 10 (10) W/cm(2)) laser ablation of silicon, and his attributed to the phenomen on of phase explosion. The threshold irradiance for phase explosion showed a dependence on two laser parameters: laser beam spot size and wavelength. For a larger beam size and longer incident wavelength, a higher laser irrad iance was required to generate phase explosion. The rapid increase of crate r depth above the phase explosion threshold irradiance correlated with a si gnificant increase in the ICPMS signal intensity. The ratio of crater volum e to ICPMS intensity, which represents entrainment efficiency, remained the lowest at laser irradiances slightly above the phase explosion threshold. However, this Patio increased at irradiances well above the threshold (> 10 (11) W/cm(2)). Chemical analysis using laser ablation at irradiance above 1 0(11) W/Cm-2 provides increased sensitivity via improved entrainment and tr ansport efficiency and increased ablation rate.