Linkage between crystallographic texture and surface roughness in niobium films synthesized by ion beam assisted deposition

The development of texture in thin films under ion bombardment is due to the preferential growth of the aligned grains in the film relative to the unaligned grains. The difference in growth rates between aligned and unaligned grains causes the surface to roughen with increasing film thickness. Hence, the development of texture and roughness are rooted in the same physical processes; differential sputtering caused by ion channeling. Experiments were performed to test the validity of a model for the development of roughness and texture. Results of Nb films deposited onto Si substrates using ion beam assisted deposition (IBAD) confirmed that both surface roughness and texture increase linearly with film thickness up to a critical value. That the critical thickness range is 114-250 nm supports a growth mechanism for texture development in Nb films