Investigation of the Dynamics of Copper Plasma Generated from a Laser-Ablated Target Using Optical Emission Analysis

Abstract

Spatially resolved and integrated spectroscopies, especially temporal emission profile measurements, were used to examine the plume emissions associated with copper plasma generated by 308-nm excimer laser ablation at reduced pressures (< 1.0 × 10−1 Pa), by which the composition and dynamics of the plasma were investigated. It is found that, even for the same emitting species, the temporal and spatial behaviors of the emissions originating from different transitions can be very different. Three types of emission lines are clearly evident, which reveal the characteristics of the plasma. The plasma forms as a result of laser ablation and evolves from breakdown of the ablation-created copper vapor to electron-collisional expansion dynamics. At the initial stage, the plasma involves a large amount of Cu(II) and high energy-excited Cu(I) species, and then evolves to consist mainly of low energy-excited Cu(I) species. The results also show that the plasma maintains higher temperature for a quite a long time, and cool electron-impacting excitations determine the plasma behavior while it expands far away from the target.