Positive ion emission from oxidized aluminum during ultraviolet excimer laser irradiation

Abstract

The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Positive ion emission Interaction of vacuum ultraviolet excimer laser radiation with fused silica. I. Positive ion emission

The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Positive ion emission

“…In the case of insulating oxides (e.g., MgO 20 and Al 2 O 3 9 ), ions emitted during UV laser exposure can display high kinetic energy ions that are consistent with Dq trap ¼ þ2jej in Eq. (2), where both electrons are ejected from the trap by laser photons.…”

“…We have previously shown that laser-induced ion emission from wide bandgap insulators originates from surface defect sites where a positive ion is sorbed on top of a surface electron trap. [1][2][3][4][5][6][7][8][9] We suggest that the corresponding defect configuration for semiconducting ZnO is a zinc ion sorbed on top of a surface oxygen vacancy. When the electron trap is photoionized by the laser, the electrostatic force on the sorbed positive ion changes sign and the ion is ejected with significant kinetic energy.…”

“…17 In Ref. 9, we show that laser-induced PIE from clean metal surfaces at fluences below the threshold for plume formation (optical breakdown) is highly unlikely.…”

“…A similar change in TOF signal with fluence was observed in the emission of Al þ from thin oxidized films on aluminum metal during 193-nm irradiation. 9 The mean and standard deviation of the kinetic energy distribution determined by fitting Eq. (1) to the signal at 220 mJ/cm 2 are 9.0 eV and 1.1 eV, respectively; signals acquired at lower fluences (not shown) yield similar kinetic energies.…”

“…Examples include MgO, 1-3 a number of alkali halides, 4,5 fused silica, 6 and more complex oxides. [7][8][9] In each case, the photon energy is well below the material's bandgap, in which case photon absorption is defect-mediated. We have shown that these emissions are due to the electrostatic ejection of ions that are sorbed atop photoionized surface electron traps.…”