Femtosecond laser ablation of gallium arsenide investigated with time-of-flight mass spectroscopy

We have investigated femtosecond laser-induced ablation of gallium arsenide using time-of-flight mass spectroscopy. At the ablation threshold, we estimated surface temperatures on the order of 3500 K. We observed a clear thresholdlike effect in the number of detected particles and with increasing fluence free flight desorption transforms into a collisional expansion process. Above the ablation threshold, the behavior of gallium particles can be quantitatively described through Knudsen-layer theory. (C) 1998 American Institute of Physics. [S0003-6951(98)03919-9].