Microstructure of epitaxial Mg₃N₂ thin films grown by MBE

The epitaxial growth of Mg3N2 thin films by molecular beam epitaxy has been recently achieved. This work presents the structural properties of the films, including grain sizes and lattice rotations, as assessed by x-ray diffraction and transmission electron microscopy. The films’ microstructure consists of well-aligned columnar grains 10 nm in diameter that nucleate at the film/substrate interface and display a significant column twist, in the order of 2.5°. As growth proceeds, tilted and twisted mosaic blocks overgrow these columns, as observed in many other epitaxial semiconductors. Yet, the rocking curves on symmetric reflections display extremely narrow peaks (∼50 arc sec), revealing a long-range spatial correlation between structural defects that should not be mistakenly considered a proof of high crystalline quality.