Growth and structural evolution of ultrathin LaAlO3 films on Al2O3 (0001) via pulsed laser deposition

This study reports the first direct growth of ultrathin LaAlO3 films on Al2O3 (0001) using pulsed laser deposition. Despite significant lattice and symmetry mismatches between the perovskite LaAlO3 and the trigonal sapphire substrates, in situ reflection high-energy electron diffraction confirms single-crystalline films with predominantly two-dimensional (2D) growth. Atomic force microscopy confirms uniform 2D growth, while ex-situ in vacuum annealing at 900◦C shows grain coarsening and uniform island formation of the film. X-ray photoelectron spectroscopy demonstrates the absence of interdiffusion at the LaAlO3/Al2O3 (0001) interface, even after high-temperature annealing (900◦C). These findings establish Al2O3 (0001) as a thermally stable substrate for the direct 2D growth of ultrathin LaAlO3 films, providing a promising platform for buffer layers, high-k di electrics, and fundamental studies of heteroepitaxy.