Energy distributions of particles ejected from laser-generated pulsed plasmas

Abstract

A study of laser ablation in vacuum of metallic elements (Al, Cu and Ta) at different boiling points is reported. A Nd:YAG laser radiation, 3 ns pulse duration and 10 9 W/cm 2 intensity, produces non-isotropic emission of neutral and ionic species. Mass quadrupole spectrometry, coupled to a 45 • electrostatic ion deflection, allows estimation of the energy distributions of the emitted species within the plasma plume as a function of the incident laser energy. Neutrals show typical Boltzmann distributions indicating the plasma temperature. Ions show Coulomb-Boltzmann-shifted distributions, typical of plasma thermal interactions, adiabatic expansion in vacuum and Coulomb interaction between charged species. Surface profiles of the craters and microscopy investigations permitted to study the ablation threshold, the ablation yields and the deposition rate of thin films on silicon substrates. The multi-component structure of the plasma plume emission is described in terms of charge state, ions and neutrals temperature and plasma density. A special regard is given to the study of the ion acceleration process occurring inside the plasma due to a high electrical field generated in the non-equilibrium plasma. : 41.75.Jv, 52.25.Jm, 52.25.Ya PACS

Experimental Research on Impulse Coupling Characteristics and Plasma Plume Dynamics of a Nanosecond Pulsed Laser Irradiated Aluminum Target

“…8 were identified according to the NIST database. As can be seen, Al + was the main Al charge state, which corresponded to the results reported by Caridi et al [31]. Therefore, the Al + whose spectral line appeared at the wavelength of 624.33 nm could be selected as the representative species to analyze the ion plume images.…”

“…The emission intensity was more distinguished for the condition of a fluence higher than 15.92 J/cm 2 . This could be interpreted with the result of [31] that the charges state increased with the laser fluence and the energetic distributions shifted towards higher energies. Additionally, with the increase of the laser fluence, the highest radiation intensity region in the plasma plume located above the target surface was observed, and it was called the plasma core [17].…”

Angular and energy distribution of Sn ion debris ejected from a laser-produced plasma source, for laser power densities in the range suitable for extreme ultraviolet lithography

“…Figure 3 decrease in the mean ion energy as a function of emission angle for all the investigated charge states and laser power densities. This is in agreement with previous charge-integrated results presented by Hansen et al 32 (1-4 Â 10 11 W/ cm 2 ) and Claeyssens et al 33 performed on Ag and C, respectively, and with charge-differentiated results presented by Caridi et al 34 for Ta ions with a laser power density in the region of 10 9 W/cm 2 . Investigating the mean ion energy as a function of ion charge for a range of emission angles, from Fig.…”

“…Ions traversing the double layer are reported to gain a substantial fraction of their final kinetic energy. 34,35,55,58 Bulgakova et al examined the angular distribution of ions due to the formation of a double layer within a plasma plume, for similar spot size conditions to those employed in this study, and found ions subjected to potential acceleration are ejected in a narrow emission cone. 35,62 The introduction of a Knudsen and/or a double layer superimposed on the supersonic adiabatic expansion of the plume can help further describe the features observed in this study.…”

Optical-vortex laser ablation

“…Tantalum (Ta) plates were used as target samples. They exhibit low ablation threshold in comparison with other metals [23][24][25], which enables us to perform ablation experiment easily. Thickness of the Ta plates was ~1 mm and the plate surfaces were polished by sandpaper.…”