%0 Journal Article %K Laser ablation %K Crater %K Electron number density %K Plasma temperature %K Laser induced plasma spectroscopy %A Haichen Liu %A Xianglei Mao %A Jong-Hyun Yoo %A Richard E Russo %B Spectrochimica Acta Part B: Atomic Spectroscopy %D 1999 %G eng %N 11 %P 1607-1624 %R 10.1016/S0584-8547(99)00092-0 %T Early phase laser induced plasma diagnostics and mass removal during single-pulse laser ablation of silicon %V 54 %2 LBNL-43861 %8 11/1999 %X

The electron number density and temperature during the early phase (<300 ns) of laser-induced plasmas from silicon using a 266-nm, 3-ns Nd:YAG laser were deduced via spectroscopic methods. These parameters were measured as a function of delay time vs. irradiance in the range of 2–80 GW/cm2, and compared with crater volume measurements. A dramatic change in plasma characteristics (electron number density, temperature, and degree of ionization) as well as a sharp increase of mass removal was observed when the irradiance was increased beyond a threshold of 20 GW/cm2. Possible mechanisms such as inverse bremsstrahlung and self-regulation were used to describe these data in the low irradiance region. Laser self-focusing and critical temperature are discussed to explain the dramatic changes after the irradiance reaches the threshold.