Effect of deposition rate on the microstructure of electron beam evaporated nanocrystalline Pd thin films

The influence of the deposition rate on the formation of growth twins in nanocrystalline Pd films deposited by electron beam evaporation is investigated using transmission electron microscopy. Statistical measurements prove that twin boundary (TB) density and volume fraction of grains containing twins increase with increasing deposition rate. A clear increase of the dislocation density was observed for the highest depositin rate of 5 Å/s, caused by the increase of the internal stress building up during deposition. Based on crystallographic orientation indexation using transmission electron microscopy, it can be concluded that a (111) crystallographic texture increases with increasing deposition rate even though the (101) crystallographic texture remains dominant. Most of the TBs coherent without any residual dislocations. However, for the highest deposition rate 5 Å/s, the coherency of the TBs decreases significantly as a result of the interactin of lattice dislocations emitted during deposition with the growth TBs. The analysis of the grain boundary character of differentPd films shows that an increasing fraction of high angle grain boundaries with misorientation angles around55-56° leads to a higher potential for twin formation.