engleski

TIME-OF-FLIGHT MASS SPECTROMETRY OF LASER INDUCED PLUME FROM METALLIC TARGETS

Pulsed laser vaporization is a very promising method for obtaining new species not observed in standard thermal prosesses. The method is very succesfully applied in deposition of thin films. Laser vaporization is a method for production of different nanoparticles and clusters. Different metal and non-metal targets can be vaporized under action of high energy pulsed laser. Laser vaporization of solid targets results with cloud of ions, electrons and neutrals formed above the surface. In our laboratory we developed a Time-of-Flight (TOF) mass spectrometry technique for detection of ionic species. In this work we concentrate on the detection of ionic species created by excimer laser (308 nm, 15 ns pulse duration) vaporization of different elements, such as Li, Cd, Zn, Al and Li/Cd alloy. Vaporization is performed in a high vacuum (approximatelly 10-6 mbar), or in a background gas (N2, H2, Ar..., approximatelly 10-4 mbar) which interacts with the vaporized species. Measurements are taken in continuous field and pulsed field work regime of TOF. We performed both spatial and time resolved TOF analysis of the vaporized cloud. Mass spectra are discussed in terms of different laser fluences, laser spot sizes and given target-TOF axis distances. We observed ions with masses 30 and 28 in nitrogen background for Li/Cd and Li targets, respectively. These results will be compared to results of vaporization with the pulsed dye laser tuned to Li(2s-3d) two-photon atomic resonance.

time of flight; laser ablation

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