Theoretical insights into laser-assisted field evaporation of ionic compounds

This study addresses the kinetic process of field evaporation of MgO assisted by ultrafast laser pulses combining density functional theory and molecular dynamics. A quantitative model is presented to describe the competitive evaporation of Mg and O ions under various conditions by comparing the activation barriers. The coordination number has a significant impact on the evaporation kinetics. The evaporation ratio of Mg to O rises with increasing DC field strength and laser intensity. Moreover, the energetics of evaporation is in correlation with photo-induced field ionization, revealing distinct mechanisms of evaporation for Mg and O. While Mg undergoes further ionization and field evaporation simultaneously, the evaporation of O is coupled with the relaxation of excited carriers. The final charge state of evaporated O is determined by the DC field strength rather than the laser intensity. Our findings provide insights into laser–matter interactions in ionic compounds and contribute to the development of atom probe techniques.