Temporally resolved laser inducedplasma diagnostics of single crystal silicon - effects of ambient pressure

Laser-Induced Breakdown Spectroscopy of silicon was performed using a nanosecond pulsed frequencydoubled Nd:YAG (532 nm) laser. The temporal evolution of the laser ablation plumes in air at atmosphericpressure and at an ambient pressure of ∼10−5 mbar is presented. Electron densities were determined fromthe Stark broadening of the Si (I) 288.16 nm emission line. Electron densities in the range of 6.91×1017 to1.29×1019 cm−3 at atmospheric pressure and 1.68×1017 to 3.02×1019 cm−3 under vacuum were observed.Electron excitation temperatures were obtained from the line to continuum ratios and yielded temperaturesin the range 7600–18,200 K at atmospheric pressure, and 8020–18,200 K under vacuum. The plasmamorphology is also characterized with respect to time in both pressure regimes