Dislocation pileup in He implanted complex oxides

The origin of the anomalous high spatial selective etch rate in a 0.4 $\mu $m-wide buried deeply implant region in complex oxides is studied. LiNbO$_{3}$ samples, prepared with 10 $\mu $m implantation depth and 5x10$^{16}$ cm$^{-2}$ He$^{+}$ fluence, show wet-etch-rate enhancement of 10$^{4}$ occurs after implantation and a narrow window (175-275 $^{\circ}$C) of low-temperature post-implantation annealing. Examination using time-resolved optical microscopy, XRD, and TEM show that this enhancement arises from the more rapid etch-solution transport in the highly dense network of dislocations pileups formed in the implanted region after annealing. Full curing of the dislocations takes place at 350 $^{\circ}$C. A mechanism for the pileups build-up and disappearance is suggested.