On the study of the oriented cracks formed in ErD2 thin film

Pure erbium (Er) film was grown on molybdenum substrate by an electron-beam evaporation deposition technique. Cracks along the {111} crystal planes of ErD2 lattice have been found to grow in ErD2 films synthesized by deuteration of metal Er films. The preferentially orientated cracks consist of polycrystalline Er2O3 particles, which are well confirmed by chemical analysis via X-ray energy dispersive spectroscopy (EDS) element mapping and selected area electron diffraction (SAED) performed in a transmission electron microscope (TEM). Two main factors are thought to account for the formation of the orientated cracks. One is the increase in local stresses caused by the phase transformation from Er to ErD2, the other is the oxygen diffusion to the favored sites in ErD2 lattice during deuteration processing.