LASER SILICON ABLATION STUDIED BY TIME-OF-FLIGHT MASS-SPECTROMETRY - GENERATION OF SI IONS AND NEUTRALS AND THEIR TRANSLATIONAL PROPERTIES

Laser pulses of Nd:YAG (532 and 266 nm) were irradiated on a Si target to investigate the ablation process. Monoatomic ions and neutrals were simultaneously ablated, with ions having higher most probable kinetic energy (MPKE) and broader velocity distribution than neutrals. The two beams showed close ablation fluence threshold, but different exponential relationships of the intensity of the ablated species vs laser fluence. with the 266 nm beam having a higher increasing rate than that of the 532 nm beam. The 266 nm beam also resulted in higher kinetic energy and a higher fraction of ions in the ejected particle stream. The time-of-flight (TOF) results fitted the shifted Maxwell-Boltzmann distribution well. The laser Si ablation mechanism was discussed.