Abstract
We use real-time diffuse surface x-ray diffraction to determine the island size distributions for individual laser shots in pulsed laser deposition (PLD) of SrTiO$_3$. Our measurements show that the island size evolution obeys dynamic scaling and the presence of two distinct regimes of island growth kinetics. These data show a decrease in island densities and a crossover from diffusion limited to attachment limited island growth kinetics that clearly contradicts the prevailing view that surface smoothing is produced by increasing island density. This previously unreported crossover reveals a fundamental change in the atomic surface transport processes that control PLD growth and is the kinetic signature for entering a quasi step flow regime. Direct measurements show that surface smoothing occurs by quasi step flow as PLD self-organizes local step flow on a length scale consistent with temperature and PLD parameters. The significance of PLD driven quasi step flow is that it is a highly adaptive local variant of ordinary step flow that occurs without need for long straight terraces and very high temperatures.
