The influence of surface contamination on the ion emission from nanosecond-pulsed laser ablation of Al and Cu

Abstract

Ions emitted from planar Al and Cu targets irradiated with a 1064 nm pulsed laser were investigated with the help of a time-resolving Langmuir probe. It was found that the intensity of the ions emitted from a target area rapidly decreases with the increasing number of laser shots, and seems to reach saturation after about 10 laser shots. The saturated intensity of Al and Cu ions was approximately 0.1 and 0.3 times the intensity of the respective ions measured at the first laser shot, respectively. The higher target ion intensity for the first few shots is thought to be due to the enhanced ionization of target atoms by vacuum-ultraviolet radiations emitted from the thermally excited/ionized surface contaminants. The reduction of target ion intensity with an increasing number of laser shots thus indicates the removal of contaminants from the irradiated surface area. Laser-cleaned Al and Cu surfaces were then allowed to be recontaminated with residual vacuum gases and the ion intensity was measured at various time delays. The prolonged exposure of the cleaned target to vacuum residual gases completely restores the ion intensity. Regarding surface contaminants removal, laser shots of higher intensities were found to be more effective than a higher number of laser shots having lower intensities.

Microstructural Design of the Cast Iron via Laser Hardening with Defocused Beam of the Continuous Wave CO2 Laser

“…l is defined via thermal factor, ltherm, and optical parameter, lop, as can be observed in equation 8 [30,31].…”

“…ltherm is determined by thermodynamic properties of the material and laser parameters, as being detailed in equation 9 [30,31]…”

“…In the case of the metallic materials processed with infrared laser, ltherm is much larger than lop [30]. Thus, thermal factor is the dominant parameter in l. ltherm is defined by τ (equation 9 [30,31]), which is in turn determined through v and Do, as can viewed in equation 10 [26].…”

“…This due to lower El and higher φth for laser scans at 4.0mm.As commented early, the increment of Z reduces the El that is determinant on the depth size. In the case of φth, larger Z generates higher values of this factor, as being indicated in equations 8 [30], 9 [30,31], 10 [26] and 11 [29].…”