Pre-equilibrium stopping and charge capture in proton-irradiated aluminum sheets

Electron cascades and secondary electron emission in graphene under energetic ion irradiation

“…Real-time TDDFT [20][21][22][23][24] explicitly approximates the quantum-mechanical electron-electron interaction and includes the electron-ion Coulomb interaction. It has recently been used to describe strong excitations in material surfaces created by either charged particles or electromagnetic radiation, 13,18,[25][26][27] and it is able to account for charge capture by the passing ion. 13 In the context of this work, we use TDDFT to describe (i) energy deposition by the ion in the electronic system of the target, (ii) subsequent electron-electron scattering and electron-hole interactions in the excited state, and (iii) emission and capture of electrons.…”

“…It has recently been used to describe strong excitations in material surfaces created by either charged particles or electromagnetic radiation, 13,18,[25][26][27] and it is able to account for charge capture by the passing ion. 13 In the context of this work, we use TDDFT to describe (i) energy deposition by the ion in the electronic system of the target, (ii) subsequent electron-electron scattering and electron-hole interactions in the excited state, and (iii) emission and capture of electrons. However, the high computational cost of this method does not allow for simulations of very heavy and fast ions as well as large graphene sheets.…”

“…( 1), for the electronic system because of its exceptional numerical accuracy for simulations of extended systems over thousands of time steps. 13,56 In the beginning of the timedependent simulation, each projectile ion starts 25 a 0 away from the graphene layer; it approaches and traverses the graphene at a constant velocity along a normal trajectory (see inset of Fig. 3).…”

“…First, the excitation modes of 2D materials can differ from their bulk counterparts, which can influence energy deposition. 13 Also, electrons excited to high energy states during a SHI impact may escape from the surface if their energy exceeds the barrier imposed by the work function. This phenomenon is known as secondary electron emission (SEE).…”

“…[14][15][16][17] In 2D materials, the electron capture starts as the ion approaches the target, but this process may not have enough time to fully complete within the material and can become disrupted upon the SHI's exit from the target. 13 Moreover, graphene might be especially efficient at supplying electrons; Refs. 18 and 19 showed that during the impact of a highly charged ion (HCI) up to 30 and 70 electrons are captured and emitted, respectively.…”