- The physical mechanisms and processes underlying the erosion of a surface induced by cluster bombardment or short-pulse laser irradiation are highlighted. When the average energy delivered per atom in the vicinity of the surface becomes comparable to the cohesive energy of the solid, sputtering from a so-called spike may result. Such a spike leads to abundant sputtering (surface erosion) and crater formation. Direct atomization in the region of highest energy deposition, as well as melt flow and gas flow contribute to the erosion. The materials phenomena occurring after ultra-fast laser irradiation of a metal in the ps- or fs-regime are reviewed. With increasing laser fluence, the film melts, voids are formed, the film tears (spallation), and finally fragments to form a multitude of clusters. These processes are universal in the sense that they occur in widely differing materials such as metals or van-der-Waals bonded materials. We investigate a Lennard-Jones solid as well as four different metals (Al, Cu, Ti, W), which vary widely in their cohesive energy, melting temperature, bulk modulus, and crystal structure. When the energy transfer starting the process is scaled to the cohesive energy of the material, the thresholds of these processes adopt similar values. A comparison of the similarities and differences of the mechanisms underlying surface erosion under cluster ion impact and ultrafast laser irradiation will be drawn.
