Sub-nanosecond Thermal Spike Induced Nanostructuring of Thin Solid Films Under Swift Heavy Ion (SHI) Irradiation

The interaction between swift heavy ions (SHI) and a solid has been identified as one of the important physical processes to generate or modify nanostructures in thin solid films. The large part of the energy which is deposited in the electronic subsystem of a material by SHI is known as electronic energy loss and gets coupled to the lattice subsystem in a complex way resulting in a transient (picoseconds to sub-nanosecond) thermal spike within a few nanometer diameter region of the thin solid film along the ion path. The temperature of this narrow zone may raise up to 1000 K or more during this time. This transient heating process is known as lattice thermal spike and can be used as a tool to engineer materials down to the nanoscale. Here we address two important consequences of lattice thermal spike; (i) elongation of metal nanoparticles embedded in dielectric thin films and (ii) generation of a-Si/c-Si nanostructures in a silicon nitride matrix.