title: Electron Elevator: Excitations across the Band Gap via a Dynamical Gap State.
abstract: We use time-dependent density functional theory to study self-irradiated Si. We calculate the electronic stopping power of Si in Si by evaluating the energy transferred to the electrons per unit path length by an ion of kinetic energy from 1 eV to 100 keV moving through the host. Electronic stopping is found to be significant below the threshold velocity normally identified with transitions across the band gap. A structured crossover at low velocity exists in place of a hard threshold. An analysis of the time dependence of the transition rates using coupled linear rate equations enables one of the excitation mechanisms to be clearly identified: a defect state induced in the gap by the moving ion acts like an elevator and carries electrons across the band gap.
authors.affiliation: Department of Physics and Thomas Young Centre, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Lim
authors.affiliation: Department of Physics and Thomas Young Centre, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: W M C
authors.initials: WM
authors.lastname: Foulkes
authors.affiliation: Department of Materials and Thomas Young Centre, Imperial College London, London SW7 2AZ, United Kingdom.
authors.forename: A P
authors.initials: AP
authors.lastname: Horsfield
authors.affiliation: CCFE, Culham Centre for Fusion Energy, Abingdon, Oxfordshire OX14 3DB, United Kingdom.
authors.forename: D R
authors.initials: DR
authors.lastname: Mason
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: A
authors.initials: A
authors.lastname: Schleife
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: E W
authors.initials: EW
authors.lastname: Draeger
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Correa