Thermal effects on laser-assisted field evaporation from a Si surface: A real-time first-principles study

• Published in: Journal of applied physics Vol. 126; no. 3
• Main Authors: Uchida, Kazuki, Suzuki, Yasumitsu, Watanabe, Kazuyuki
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 21.07.2019
• Subjects: Applied physics; Density functional theory; Electric fields; Electron energy; Electron transfer; Evaporation; Evaporation rate; Excitation; First principles; Laser ablation; Lasers; Real time; Temperature effects; Time dependence
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.5090949

This work assessed thermal effects on laser-assisted field evaporation from a Si surface using real-time time-dependent density functional theory calculations. These assessments focused on finite electron and lattice temperatures, both of which were characterized on different time scales. The results show that dangling bonds at clean surfaces assist thermal excitation in response to increased finite electron temperature. It was also determined that thermal excitation induces electron transfer from the surface to the interior of Si in the presence of an electrostatic field, resulting in ionization of the surface atoms. The finite electron temperature effect on evaporation dynamics, however, was found to be negligible. In contrast, increases in the finite lattice temperature evidently induce atomic motion both parallel and perpendicular to the surface, thus appreciably enhancing the evaporation rate in the presence of electrostatic and laser fields. The real-time first-principles simulations “without empirical parameters” presented herein provide theoretical evidence for thermal effects during laser-assisted field evaporation, and this method should also be applicable to various nonequilibrium thermal phenomena, such as laser ablation.