Time of flight mass spectroscopy of femtosecond laser ablation of solid surfaces
P SOC PHOTO-OPT INS 3343 (1998) 334-343
Abstract:
We have investigated femtosecond laser-induced ablation of gallium arsenide and silicon using time-of-flight mass spectroscopy. Below the ablation threshold we observe free flight desorption of atoms from the laser heated surface. The absence of collisions between particles leaving the solid allows to obtain the maximum surface temperature during laser irradiation of Gallium Arsenide. We estimated maximum surface temperatures of the order of 3500 K at the ablation threshold, where we observed a step-like increase in the number of detected particles. In the case of Silicon the existence of molecules of up to 6 atoms does not allow to measure the surface temperature. With increasing fluence free flight desorption transforms into a collisional expansion process. The behaviour of Gallium particles can be quantitatively described through Knudsen-layer theory, indicating that Gallium particles expand as a non-ideal gas close to the ablation threshold (gamma=Cv/Cp<5/3). Above fluences of approximately 2.5 Fth gamma approaches 5/3 indicating an ideal gas behaviour for the expanding material. Dilution into the two phase regime of a superheated liquid characterises ablation close to threshold.Time resolved studies of femtosecond laser induced ablation from solid surfaces
SPRINGER SERIES CHEM 63 (1998) 316-318
Abstract:
Ultrafast time resolved microscopy has been used to study the dynamics of femtosecond laser induced ablation from the surfaces of various semiconductors and metals. Upon ablation initially metallic matter transforms into a transparent state with a high index of refraction.Transient states of matter during short pulse laser ablation
PHYSICAL REVIEW LETTERS 81:1 (1998) 224-227
Coherent acoustic oscillations in metallic nanoparticles generated with femtosecond optical pulses
PHYSICAL REVIEW B 55:20 (1997) 13424-13427
fs spectroscopy of phonon emission and absorption for a cold plasma in gallium arsenide
MATER RES SOC SYMP P 397 (1996) 21-26