Nano-hillock formation in diamond-like carbon induced by swift heavy projectiles in the electronic stopping regime: Experiments and atomistic simulations

The formation of surface hillocks in diamond-like carbon is studied experimentally and by means of large-scale molecular dynamics simulations with 5 × 106 atoms combined with a thermal spike model. The irradiation experiments with swift heavy ions cover a large electronic stopping range between ∼12 and 72 keV/nm. Both experiments and simulations show that beyond a stopping power threshold, the hillock height increases linearly with the electronic stopping, and agree extremely well assuming an efficiency of approximately 20% in the transfer of electronic energy to the lattice. The simulations also show a transition of sp3 to sp2bonding along the tracks with the hillocks containing almost no sp3 contribution.Fil: Schwen, D.. University of Illinois at Urbana-Champaign. Department of Materials Science and Engineering; Estados UnidosFil: Bringa, Eduardo Marcial. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Krauser, J.. Hochschule Harz; AlemaniaFil: Weidinger, A.. Helmholtz-Zentrum Berlin fur Materialien und Energie; AlemaniaFil: Trautmann, C.. GSI Helmholtzzentrum; AlemaniaFil: Hofsass, H.. Universitat Gottingen. Physikalisches Institut; Alemani

Lattice sites of Li in CdTe

The lattice site occupation of Li in CdTe at temperatures between 40 and 500 K was investigated with the emission channeling method. Radioactive Li-8 ions were implanted at low doses into CdTe single crystals. Emission channeling patterns of alpha-particles emitted in the nuclear decay of Li-8 (t(1/2) = 838 ms) were measured and compared to calculated emission channeling and blocking effects. At temperatures below 130 K the Li ions occupy mainly tetrahedral interstitial sites and about 10% substitutional sites. In the temperature range between 130 and 190 K, a site change from the tetrahedral interstitial sites to substitutional sites is observed. Between 190 and 470 K, in addition to the substitutional Li, all samples show Li at sites, which are displaced 0.7(1) Angstrom from the substitutional position, either along the [111] axis or [100] axis. Above 470 K out-diffusion of Li to the surface is observed

Thermal stability of substitutional ag in CdTe

The thermal stability of substitutional Ag in CdTe was deduced from lattice location measurements at different temperatures. Substitutional Ag probe atoms were generated via transmutation doping from radioactive Cd isotopes. The lattice sites of Ag isotopes were determined by measuring the channeling effects of emitted conversion electrons. Below room temperature Ag occupies mainly substitutional lattice sites. With increasing measurement temperature the substitutional fraction of Ag atoms decreases and vanishes completely above 400 K. Simultaneously measured loss of Ag activity indicates that some of the Ag diffuses preferentially to the surface where it disappears. The remaining Ag may be trapped at extended defect complexes or precipitates. In Cd-rich CdTe we suspect an interstitial diffusion directly after the dissociation to the sinks, whereas in Te-rich CdTe this process is possibly retarded by retrapping at Cd vacancies