Laser-Assisted Field Evaporation
Résumé
After an introduction on the history of laser-assisted field evaporation of metallic and nonmetallic samples, the evaporation mechanisms of surface atoms in laser-assisted atom probe tomography (La-APT) are presented and discussed with an emphasis on the laser–matter interaction when the sample is a nanometric tip submitted to a high electric field. In the case of metallic samples, we will discuss the evaporation behavior under laser illumination using numerical simulations of optical absorption maps of the nanosamples coupled with numerical solutions of two-temperature model equations, to determine the tip temperature evolution after the interaction with the laser pulse. This multiphysics model is used to interpret the experimental results and predict the evaporation dynamics of metallic samples as a function of the illumination conditions (wavelength, repetition rate, and polarization) and tip shape. The evaporation behavior of band-gap materials (semiconductors and oxides) under laser illumination will be presented, taking into account the change of the surface optical properties of these materials due to the band bending induced at the surface by the strong static field, diffraction effects, and photon-induced conductivity of the samples. All these effects are presented and studied to determine the physical mechanisms of the evaporation of nonmetallic materials in La-APT. Moreover, we will show that La-APT can be used as an original experimental setup to study (1) the absorption of nanometric tips; (2) the contribution of the standing field to this laser energy absorption, and (3) the heating and cooling process of nanometric sample after the interaction with ultrafast laser.