Modeling of pulsed-laser-induced gas detrapping, chemical reactions, diffusion, and desorption

Abstract

Short, intense laser pulses can thermally desorb hydrogen and other gases from the near surface (∼1 μm) of solids. This can be used, with some advantages, to study the trapping mechanisms, whether physical or chemical, the diffusion, and the surface recombination of these gases. By assuming a laser pulse with a Gaussian time profile, these successive steps are modeled with a finite difference code by using realistic temperature- and concentration-dependent material parameters. We show explicit results for the magnitude of the desorption puff as a function of the laser energy and for the depth profiles of the remaining gas under various assumptions for the detrapping mechanism, the diffusion coefficient, and the surface recombination coefficient. The results demonstrate that in spite of the poorer control on temperature, compared to isochronal or ramp anneals, the rate-limiting process can be identified and the activation energies determined.