Speaker: P Sen (pdf slides 1.5 Mb).

Abstract: Swift MeV ions can travel deep inside a lattice (even in the absence of channeling), concomitant with large electronic energy loss. This method of energy transfer makes this a gradual process, spread over several layers of lattice atoms. The effect of large electronic energy loss depends on the material type. For example, a metal is quickly returned to its normal state, sharing much of the energy with the screening electrons. On the other hand, an insulator like mica cannot do so, leaving atoms momentarily charged along the ion path. These charged atoms can interact violently through Coulomb forces leading to atomic displacements (called Coulomb explosion) and track formation in insulators. For semiconductors, the situation can be complex, but interesting. I shall describe the evolution of a hitherto unknown modification of single crystalline materials by the way of MeV ion irradiation. The ions deform the single crystals at predetermined regions, spatially separated from the irradiation event through nonlinear transport of energy along atomic chains. I shall provide a background to the problem and their consequences, with applications.

NLDD05, Nonlinear excitations: theory and experiments, Sevilla, March 3-4, 2005.