Electron-ion dynamics in laser-assisted desorption of hydrogen atoms from H-Si(111) surface

Abstract

In the framework of real time real space time-dependent density functional theory we have studied the electron-ion dynamics of a hydrogen-terminated silicon surface H-Si(111) subjected to intense laser irradiation. Two surface fragments of different sizes have been used in the simulations. When the intensity and duration of the laser exceed certain levels (which depend on the wavelength) we observe the desorption of the hydrogen atoms, while the underlying silicon layer remains essentially undamaged. Upon further increase of the laser intensity, the chemical bonds between silicon atoms break as well. The results of the simulations suggest that with an appropriate choice of laser parameters it should be possible to remove the hydrogen layer from the H-Si(111) surface in a matter of a few tens of femtoseconds. We have also observed that at high laser field intensities (2-4 V=Å in this work) the desorption occurs even when the laser frequency is smaller than the optical gap of the silicon surface fragments. Therefore, nonlinear phenomena must play an essential role in such desorption processes.

Simulation of high-energy ion collisions with graphene fragments

“…TDDFT has been successfully used in various timedependent quantum mechanical simulations, e.g., in nonperturbative calculations of properties of systems in intense laser fields [32][33][34] or to study the scattering of energetic atoms with carbon nanostructures 31,35,36 .…”

First-principles molecular-dynamics simulation of biphenyl under strong laser pulses by time-dependent density-functional theory

“…The main framework of this approach is similar to that for TDDFT simulation of Coulomb explosion dynamics in Ref. [32] and other incident laser reaction dynamics in the literature [33,34]. The electron system is described by the TD Kohn-Sham equation, and the ions are assumed to be classical particles moving under Hellmann-Feynman forces [35]; therefore, the TDDFT-MD simulation follows the Ehrenfest dynamics.…”

Excited-state electronic coherence in vinyl bromide ions

“…The electron dynamics is described in the framework of TDDFT [34] using a real-space grid with real-time propagation. This formalism was previously used by our group to describe Coulomb explosion of molecules [35][36][37], electron dynamics in graphene and silicon subject to intense laser pulses [38][39][40], and high energy irradiation of materials [41,42].…”