Fig. 1: Dynamic layer rearrangement revealed in RHEED rocking curves during shuttered deposition.

The diffracted-beam rocking curve shape depends only on net Sr coverage on the TiO₂ termination and is stable during anneals. a RHEED on perovskites. Layered ABO₃ crystal structure along (001) growth direction, and RHEED image of TiO₂-terminated SrTiO₃(001) surface with beam along (100) azimuth. Diffracted reflections are encircled by red ellipses inside which the (average) intensity is monitored; specular (0,0) reflection is also indicated. b RHEED diffracted intensity rocking curves. Left panel: rocking curves during Sr deposition starting on TiO₂ termination. Curves are measured during growth interruptions after Sr deposition in 0.2 monolayer increments, repeated to a total of 1.4 Sr layers; intensities are normalized to the maximum of each scan. Right panel: return to TiO₂ termination by Ti deposition in 0.2 monolayer increments. Note the similarity of the rocking curves for the same net Sr coverage (e.g., compare “Sr +0.6” and “Sr +1.4 followed by Ti +0.8”). Gray lines are guides to the eye for the peak positions, and curves are shifted for clarity. c RHEED diffracted intensity oscillations during shuttered STO growth of Sr₁/Ti₁ cycles (Sr in red, Ti in blue) at ~2.5° beam incidence (vertical dashed line in (b)). The first cycle is broken into 3 segments of Sr (red) or Ti (blue) deposition, separated by anneals (black), followed by 3 complete Sr₁/Ti₁ cycles. The starting surface has ~0.5 SrO atomic layer on TiO₂ termination. On the last cycle, open circles (860–920 s) are intensities taken from the rocking curves at equivalent Sr coverage.