Search

The idea of using carbon nanotubes (CNTs) as masks against irradiation has recently emerged, because of the region of a given material covered by a CNT can be protected from the effects of irradiation, creating nanowires. In this case, it is interesting to know in detail the number of generated recoils and their energy. In order to obtain these data, we simulate the irradiation of CNTs with carbon ions using a molecular dynamics code. To describe the interaction between carbon ions we use the Brenner potential joined smoothly to the Universal ZBL potential at short distances. We have analyzed the energy distributions of the carbon atoms emerging from the CNT for single projectile irradiation with incident energies from 30 eV to 5 keV. Our results show that the number and the energy of the recoil carbon atoms emerging from the CNT increases with the projectile incident energy. In average, each projectile with incident energy of 1 keV produces ∼3.6 recoils, which have a mean energy of 150 eV, while projectiles with 5 keV produce ∼7 recoils with a mean energy of 400 eV. [ABSTRACT FROM AUTHOR]

Abstract: The electronic energy loss of swift H and He ions in solid Ag is studied theoretically within the dielectric formalism, considering the different equilibrium charge states of the projectile inside the target. Excitation of the weakly-bound (outer) electrons is described by a superposition of Mermin-type energy-loss functions, whereas the contribution to the projectile energy loss due to the ionization of the K, L and M shells of the Ag atoms is included through hydrogenic or numerical generalized oscillator strengths. This method is used to evaluate the stopping power and the energy-loss straggling parameter of H and He ions in Ag as a function of the projectile energy, showing a good agreement with available experimental data. The contribution of the target inner-shells to the energy loss begins to be appreciable at projectile energies larger than a few hundred keV/u, being more important for the energy-loss straggling parameter than for the stopping cross section. [Copyright &y& Elsevier]

Abstract: We calculate the electronic energy loss of swift H+ and He+ ion beams in several solids with applications in material science and microelectronics, namely Ti, Fe, Ge, Pd, LiF and Si3N4. Our calculations are based on the dielectric formalism, where the charge density of the projectile is described by the Brandt–Kitagawa model, with the addition of projectile polarization. We take into account the different charge states of the projectile inside the target and the energy loss due to electron capture and loss processes. Using a realistic description of the target energy loss function, we obtain results that show a good agreement with available experimental data in a wide range of projectile energies. [Copyright &y& Elsevier]

Abstract: We have theoretically studied the electronic stopping cross section and the energy loss straggling of swift light ions (H+ and He+) moving through several compound semiconductors (GaAs, ZnSe, InP and SiC) as a function of the incident projectile energy. The calculations have been done using the dielectric formalism, in which the electronic structure of the projectile is described by the modified Brandt–Kitagawa model and the energy loss function (ELF) of the semiconductors is obtained using a linear combination of Mermin-type ELF to describe the outer electron excitations and generalized oscillator strengths to take into account the excitations of the inner-shell electrons. The different charge states that the projectile can acquire during its travel through the solid, as a result of electronic capture and loss processes, has been also considered. The contributions to the projectile energy loss from both the outer- and the inner-shell electron excitations are analyzed. The comparison of our calculated stopping cross sections with available experimental data shows a good agreement in a wide range of incident projectile energies. [Copyright &y& Elsevier]