Laser-assisted field evaporation from insulators triggered by photoinduced hole accumulation

Abstract

We analyze the mechanism of laser-assisted field evaporation from insulators triggered by photoinduced hole accumulation at the tip apex. The effects of hole accumulation on the electric flux line and the activation barrier for field evaporation are analyzed by the boundary element method with a mesoscopic model and atomistic ab initio calculations. The ab initio calculations indicate that a certain amount of hole accumulation reduces the activation barrier for field evaporation substantially. We propose the following scenario for laser-assisted field evaporation from insulators: 1) a laser pulse creates holes in the valence band of oxide through electronic excitation, 2) the holes accumulate at the tip apex due to the external direct-current electric field, 3) the positive charge at the apex reduces the activation barrier for cation evaporation, 4) the cation evaporates from the apex, and 5) the next laser pulse creates holes again and triggers subsequent field evaporations.