Thermal exfoliation and crystallographic transformation of single-crystal metal oxides induced by He-ion implantation

We report on the thermal exfoliation of 7 μm thick films from 3.8 MeV He ion-implanted single-crystal 0.955 Pb(Zn1/3Nb2/3)O3-0.045 PbTiO3 [(PZN-PT) with 4.5% PT] by rapid thermal processing. Comparison with z-cut LiNbO3 shows a significantly higher exfoliation threshold temperature in PZN-PT for the same implantation conditions. Unusually large strains in the through-implanted layer are induced in the relaxor ferroelectric PZN-PT upon ion implantation leading to a crystallographic phase transformation in that material that is not observed in LiNbO3. Depth profile analysis of the refractive index shows a much larger refractive index modulation due to nuclear collisions than in LiNbO3. The higher exfoliation temperature observed for PZN-PT, despite a larger impact of the ion implantation on material structure, suggests that the electronic polarizability and elastic response of relaxor ferroelectrics near the morphotropic phase boundary have a significant impact on the crack propagation process responsible for thermally induced exfoliation