Time-resolved x-ray monitoring of laser ablation of and plasma formation from Si

We present x-ray absorption measurements on silicon clusters and silicon plasmas produced by pulsed laser irradiation of bulk silicon. The results are compared with earlier time-resolved x-ray absorption measurements on amorphous silicon foils under pulsed laser irradiation. Clusters are formed at an irradiance as low as 3.0 J/cm2. At an irradiance of 14 J/cm2 ionized species up to Si4+ are formed. We find a removed Si layer thickness of 80 Å at an irradiance of [approximately-equal-to]6 J/cm2, at 15 ns pulse duration