Materials modification with high energy heavy ions

Fast ions moving through condensed matter produce a track of excitations and ionizations that can have lasting effects depending on the properties of the medium. Latent tracks or columnar defects are always produced in insulators. These columnar defects have been used to modify the properties of high temperature superconductors by pinning the vortices. The effect of pinning is also observed in the microwave frequency regime. With the use of higher energy heavy ions electronic loss induced effects are now observed even for metals. There seems to exist a threshold electronic stopping power for each material above which latent tracks can be produced. Creation and annealing of defects due to the heavy ion energy locked into electronic excitations needs to be understood. It is observed that below the threshold, electronic stopping power (S-e) can even provide annealing effects. The nuclear stopping power (S-e) is predominant at lower energies, i.e. towards the end of the range of the high energy ions. The extent of lattice deformation in the spatially separated electronic and nuclear loss region has been examined in Si crystal with a 100 MeV Ti beam using X-ray topography. An attempt is made to study the transient behavior of the defects produced by S-e in cuprate superconductors. The microstructure changes associated with 85 MeV Ni ion irradiation have been studied along with the hydrogen concentration variations in diamond-like carbon films.