Laser-induced fluorescence and Langmuir probe studies of copper photoablation

Abstract

Following the photoablation of copper metal targets with wavelengths of 193, 248, and 351 nm, laser-induced fluorescence (LIF) and Langmuir probe measurements have been made in the etch plume. Langmuir probe data give results for overall ion energy and density and electron temperature on a microsecond time scale. LIF probing of the plume gives results for Cu0, Cu2, and Cu+ densities and respective kinetic energies. The object is to test the various theories and concepts that have been invoked to explain the energy and density dependence on fluence and etch laser wavelength. The results support the importance of plasma effects. First, the role of plasma potentials in accelerating the ions is present even with submonolayer removal rates and with nonluminous plasma; and, second, close coupling does exist for the transfer of ion energy into atom motion.