Observation of bulk Bragg-reflection using reflection high-energy electron diffraction on Mn₃O₄-like films grown on MgO (001) by molecular beam epitaxy

Bulk Bragg diffraction spots are observed in the reflection high-energy electron diffraction (RHEED) pattern of Mn₃O₄-like films, whose surfaces consist of truncated-pyramid hillocks. The bulk Bragg diffraction spots are superposed on sharp streaks due to the flat top-face of the truncated pyramids. The appearance of the bulk Bragg diffraction spots is found to be critically dependent on the surface morphology. The incidence of the electron beam at the side facets of the truncated pyramids is found to give rise to the bulk Bragg diffraction spots. It is found that the incident angle of the electron beam with respect to the facet plane should be larger than 11° to observe bulk Bragg diffraction spots from the Mn₃O₄-like films. In the Bragg diffraction spots, a kinematically forbidden 006 diffraction spot has been observed, which can be attributed to a dynamic diffraction effect. Based upon the RHEED patterns, the crystal structure and lattice parameters of the films are directly obtained.