Characterization of the recovery and recrystallization of SrTiO 3 surface by ion channeling

The response of amorphous SrTiO ₃ (STO) films, deposited by sputtering on STO single crystalline substrates, to thermal annealing has been investigated using 950 keV He ⁺ ion channeling. During annealing, the amorphous films (∼ 560 Å thick) crystallize epitaxially with the underlying substrate by solid phase epitaxy (SPE). The crystallized films are defective. The defect level first decreases with increasing annealing temperature in the range of 400-800°C, and then increases with increasing temperature in the range of 800-1100°C. This is thought to result from the competition during annealing between SPE and the formation of randomly oriented crystallites that becomes a dominant process at high temperatures. The recovery of full crystallinity of the STO substrate with a 560 Å thick amorphous layer requires a two-step annealing sequence, i.e., annealing at 800°C followed by annealing at 1100°C. The single crystal substrates with a thin STO amorphous layer up to 80 Å thick can be completely recovered by a single-step annealing at 1100°C for 30 min.